From blaktony86 at yahoo.com Wed Jul 1 00:03:46 2009 From: blaktony86 at yahoo.com (TONY B) Date: Tue, 30 Jun 2009 10:03:46 CDT Subject: [ATM] Tessellated Blank Ronchi .. Coherency! Message-ID: Excellent progress and persistence!! I still have a feeling your problems are in the silicone adhesive. Too much flexure i would assume. Perhaps a more rigid sealant would perform better. -----Original Message----- Date: Monday, June 29, 2009 11:01:49 pm To: atm at atmlist.net From: vorblesnak at peak.org Subject: [ATM] Tessellated Blank Ronchi .. Coherency! It is nice when things work. This shot was taken after I pulled the blank off the machine for the night. Prior to this each element of the tessellation had it's own ronchi. I was wondering if it would just test that way and that is why I ended my last report with questions about figuring. I have no less work ahead of me but at least the mirrors are all pointing the same way now. http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/Tessellated%20Ronchi.JPG David Davis Toledo, OR 97391 _______________________________________________ ATM mailing list http://www.atmlist.net/ From jbentz at inreach.com Wed Jul 1 03:58:14 2009 From: jbentz at inreach.com (Jan Bentz) Date: Tue, 30 Jun 2009 11:58:14 -0700 Subject: [ATM] large aluminum mirrors In-Reply-To: <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> Message-ID: <4A4A6046.4010701@inreach.com> Michael Coslo wrote: > > On Jun 27, 2009, at 5:34 PM, Mark Holm wrote: > >> I just don't understand why people keep thinking aluminum will make >> lighter mirrors. Density is actually higher than glass and modulus >> is only a bit higher. The two pretty much cancel each other out. >> Will a real mechanical or structural engineer address this? All >> others, keep quiet. > > > > Okay, just let us know when us unwashed can join in..... ;^) Since I > play a mechanical engineer on TV, I'll chime in. > > The reason that people keep bringing up Al is that it is cheap and > potentially really easy to work with. > > If they include lightweight in the mix, they are kinda wrong - > although it is disturbingly easy to honeycomb an Al mirror blank. > Accurately following the front surface contour is not even that much > more difficult, It' is almost irresistible for many people who like > to make things to take a stab at an Al mirror. > > Problem is that Al has some other issues that make it not so > desirable. Everyone who has tried to make an Al mirror knows them. > > I have no doubt that with enough time and money, good mirrors could > be made from Al. I suspect that anything we come up with will no > longer be cheap or easy, negating my first point above. > > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > Mike -- You are certainly right in thinking it will take an adventurous soul to try Al but there have been a couple of large successful mirrors made of Al and many experiments mostly having to do with the method of manufacture and treatment of the blank. Casting, forging, rolling & welding have all been tried. The flats or spheres figured on them have exibited various degrees of figure change with time. Some methods are quite promising showing only a small fraction of a fringe change while others will change several fringes. It appears that the heat treatment they undergo vs. the environment they will operate in is the most important factor. Many of these experiments were done with an eye toward operation in hostile environments so the blank preparation is not directly applicable to our operating conditions. The main attraction of Al blanks is mainly the ease of lightweighting and its outstanding "figure of merit". The last has to do with a dimensionless number Andre Couder came up with decades ago. It was a combination of thermal diffusivity, thermal merit and specific stiffness. I'm not sure how valid this is but Al ranked quite high on the scale compared with other blank materials. Jan Bentz From toolontop at yahoo.com Wed Jul 1 03:41:49 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Tue, 30 Jun 2009 11:41:49 -0700 (PDT) Subject: [ATM] Tessellated Mirror Picture Message-ID: <471187.86863.qm@web112419.mail.gq1.yahoo.com> Hi David, Sorry, you ended up in my Yahoo spam, but you've got good company there I see now. :) 3 inch hexes - ok - that means the latest picture is looking quite good. As I recall the foam glass discussions, you're going to continue to see edge problems on the individual segments whenever they go out from under the edge of the polisher, so I'd think the best way to finish one of these would be with an oversize lap. Not something I've done with a fast mirror though. The edges are polishing first on the segments likely because they are unrestrained and the Twymann effect is causing them to warp as they polish. As you're seeing already that'll go away eventually. I recently had a 14.7x.8" f/4.2 quartz mirror (finished!) gain 20% correction overall when I removed a slightly scratched sapphire coating from the bank of the blank! Best, Mark --- On Thu, 6/25/09, vorblesnak at peak.org wrote: > From: vorblesnak at peak.org > Subject: Tessellated Mirror Picture > To: toolontop at yahoo.com > Date: Thursday, June 25, 2009, 8:26 PM > The mirror is made by gluing 3 inch > hexagons to a glass foam backer. The > glass foam has the basic curve milled into it and the > hexagons are worked > like a block of lenses. > > The idea is to be able to make a mirror of very large size, > say in the 2 > meter range, without having to handle large chunks of > glass. The idea came > to me from looking at the Keck. Then I found a whole long > discussion on > the list dated June 2008. The list folks were talking > active control. I > said why not a monolithic structure. Well, they had argued > it all out > prior to this and were not interested for the most part. So > I glued it up > and I am grinding it. > > The picture is of a 18 inch F3 mirror. You can see a > picture of the mirror > in my upload section on the atm list. The picture was to > show the > strangeness of the polish. It is polishing from the middle > out, which is > normal, but the individual hexes are polishing from the > edge in, which is > weird. But it is polishing. I have about 7 hours into it > now and I am > making headway but it is like any mirror, slow and > exacting. > > What more can I tell you? > > David Davis > Toledo, OR 97391 > > > > > > From wkitty42 at windstream.net Wed Jul 1 04:46:14 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Tue, 30 Jun 2009 15:46:14 -0400 Subject: [ATM] Tessellated Mirror Picture In-Reply-To: <471187.86863.qm@web112419.mail.gq1.yahoo.com> References: <471187.86863.qm@web112419.mail.gq1.yahoo.com> Message-ID: <4A4A6B86.9010001@windstream.net> Mark Cowan wrote: > I recently had a 14.7x.8" f/4.2 quartz mirror (finished!) gain 20% correction overall when I removed a slightly scratched sapphire coating from the bank of the blank! from the /back/ of the mirror? that would seem to indicate that it was causing the mirror to flex and not be properly flat... interesting... very interesting... -- _\/ (@@) Waldo Kitty, Waldo's Place USA __ooO_( )_Ooo_____________________ telnet://bbs.wpusa.dynip.com _|_____|_____|_____|_____|_____|_____ http://www.wpusa.dynip.com ____|_____|_____|_____|_____|_____|____ ftp://ftp.wpusa.dynip.com _|_Eat_SPAM_to_email_me!_YUM!__|_____ wkitty42 -at- windstream.net From rmay at nethere.com Wed Jul 1 05:19:10 2009 From: rmay at nethere.com (Bob May) Date: Tue, 30 Jun 2009 13:19:10 -0700 Subject: [ATM] Tessellated Blank Ronchi .. Coherency! References: <1508.69.59.200.230.1246334403.squirrel@webmail.peak.org> Message-ID: <000e01c9f9c0$07db0100$2d985545@amd> Looks like most of it is complying with the general spherical shape. There are spots tho that aren't fitting in well. I'd see about a lighter lap if possible to keep the glass from flexing. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From toolontop at yahoo.com Wed Jul 1 06:08:47 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Tue, 30 Jun 2009 14:08:47 -0700 (PDT) Subject: [ATM] Tessellated Mirror Picture Message-ID: <366838.24362.qm@web112410.mail.gq1.yahoo.com> My take is that the sapphire coating had stressed the back of the mirror - it was hard as nails (something put onto these semiconducter industry blanks to make them last longer under plasma exposure). Removing it by grinding overpowered the Twymann effect for a polished surface -> rough surface, which would have removed correction from the other side while increasing strain (I've seen that too). It hadn't any effect on the blank that was noticeable, but after being worked and then releasing the strain it obviously shifted the optical side. Stressed blank polishing uses this sort of effect - what was interesting was that it was perfectly overcorrected! Best, Mark --- On Tue, 6/30/09, waldo kitty wrote: > From: waldo kitty > Subject: Re: [ATM] Tessellated Mirror Picture > To: atm at atmlist.net > Date: Tuesday, June 30, 2009, 12:46 PM > Mark Cowan wrote: > > I recently had a 14.7x.8" f/4.2 quartz mirror > (finished!) gain 20% correction overall when I removed a > slightly scratched sapphire coating from the bank of the > blank! > > from the /back/ of the mirror? > > that would seem to indicate that it was causing the mirror > to flex and not be properly flat... interesting... very > interesting... > > --? ? ? ? _\/ > ? ? ? (@@)? ? ? ? ? > ? ? ? ? ? ? Waldo Kitty, > Waldo's Place USA > __ooO_( )_Ooo_____________________ > telnet://bbs.wpusa.dynip.com > _|_____|_____|_____|_____|_____|_____ http://www.wpusa.dynip.com > ____|_____|_____|_____|_____|_____|____ ftp://ftp.wpusa.dynip.com > _|_Eat_SPAM_to_email_me!_YUM!__|_____ wkitty42 -at- > windstream.net > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From holmmarkd at gmail.com Wed Jul 1 10:40:16 2009 From: holmmarkd at gmail.com (Mark Holm) Date: Tue, 30 Jun 2009 21:40:16 -0400 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4A6046.4010701@inreach.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> Message-ID: <4A4ABE80.3050206@gmail.com> Amateurs need to keep in mind that while aluminum has high thermal conductivity, the major deterrent to quick thermal equilibration in atm sized mirrors is the air boundary layer. Unless you are blowing the boundary layer away with fans, it won't matter much how good the thermal conductivity of the material is. I'm not making this up. Practical work by practical atm's has already proved it. Jan Bentz wrote: > > The main attraction of Al blanks is mainly the ease of lightweighting > and its outstanding "figure of merit". The last has to do with a > dimensionless number Andre Couder came up with decades ago. It was a > combination of thermal diffusivity, thermal merit and specific stiffness. > I'm not sure how valid this is but Al ranked quite high on the scale > compared with other blank materials. > > Jan Bentz > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -- Mark Holm markholm at verizon.net holmmarkd at gmail.com From jbentz at inreach.com Wed Jul 1 10:52:43 2009 From: jbentz at inreach.com (Jan Bentz) Date: Tue, 30 Jun 2009 18:52:43 -0700 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4ABE80.3050206@gmail.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <4A4ABE80.3050206@gmail.com> Message-ID: <4A4AC16B.9090609@inreach.com> Mark Holm wrote: > Amateurs need to keep in mind that while aluminum has high thermal > conductivity, the major deterrent to quick thermal equilibration in > atm sized mirrors is the air boundary layer. Unless you are blowing > the boundary layer away with fans, it won't matter much how good the > thermal conductivity of the material is. I'm not making this up. > Practical work by practical atm's has already proved it. > > Jan Bentz wrote: > >> >> The main attraction of Al blanks is mainly the ease of lightweighting >> and its outstanding "figure of merit". The last has to do with a >> dimensionless number Andre Couder came up with decades ago. It was a >> combination of thermal diffusivity, thermal merit and specific >> stiffness. >> I'm not sure how valid this is but Al ranked quite high on the scale >> compared with other blank materials. >> >> Jan Bentz >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > > Mark -- Quite so but with its high conductivity the entire mirror will reach equilibrium much faster than a glass one with or without fans. -- Jan From s.truitt at hawaiiantel.net Wed Jul 1 11:30:39 2009 From: s.truitt at hawaiiantel.net (Stan Truitt) Date: Tue, 30 Jun 2009 16:30:39 -1000 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4ABE80.3050206@gmail.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <4A4ABE80.3050206@gmail.com> Message-ID: Aloha Mark, >Amateurs need to keep in mind that while aluminum has high thermal >conductivity, the major deterrent to quick thermal equilibration in >atm sized mirrors is the air boundary layer. Unless you are blowing >the boundary layer away with fans, it won't matter much how good the >thermal conductivity of the material is. I'm not making this up. >Practical work by practical atm's has already proved it. Along with the ease of machining, advantages in being able to readily provide fluid circulation paths in contact with, or an integral part of, the mirror blank's structure; allows significant advantages in vibrationless heat exchange, far beyond that of fans. Machining slots or simply drilling holes between cells give simple and convenient design opportunities for thermal improvement. Designed in, controlled fluid circulation, trumps fans every time, and does not preclude their use. Friendly regards, Stan Truitt From vorblesnak at peak.org Wed Jul 1 07:26:27 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Tue, 30 Jun 2009 15:26:27 -0700 (PDT) Subject: [ATM] Tessellated Mirror Picture In-Reply-To: <471187.86863.qm@web112419.mail.gq1.yahoo.com> References: <471187.86863.qm@web112419.mail.gq1.yahoo.com> Message-ID: <25496.159.121.96.200.1246400787.squirrel@webmail.peak.org> A couple of folks have suggested either an oversized lap or a full sized lap to finish the polishing work. The mirror is probably about 17 inches across. I am using a 12 inch lap. Anyone care to specify a size and a why? I am willing to make that move if it will bring this thing to polish and figure. I was thinking earlier, there had been some concern expressed about crushing the glass foam slightly as polishing progressed. This would have the affect of changing the curve with every polishing cycle. I usually cold press at the end of a polishing day adding a lead ring, (about 25 pounds), to the top of the stack. I began to wonder if that might also damage the glass foam curve. David Davis Toledo, OR 97391 > > Hi David, > > Sorry, you ended up in my Yahoo spam, but you've got good company there I > see now. :) > > 3 inch hexes - ok - that means the latest picture is looking quite good. > As I recall the foam glass discussions, you're going to continue to see > edge problems on the individual segments whenever they go out from under > the edge of the polisher, so I'd think the best way to finish one of these > would be with an oversize lap. Not something I've done with a fast mirror > though. > > The edges are polishing first on the segments likely because they are > unrestrained and the Twymann effect is causing them to warp as they > polish. As you're seeing already that'll go away eventually. I recently > had a 14.7x.8" f/4.2 quartz mirror (finished!) gain 20% correction overall > when I removed a slightly scratched sapphire coating from the bank of the > blank! > > Best, > Mark > > --- On Thu, 6/25/09, vorblesnak at peak.org wrote: > >> From: vorblesnak at peak.org >> Subject: Tessellated Mirror Picture >> To: toolontop at yahoo.com >> Date: Thursday, June 25, 2009, 8:26 PM >> The mirror is made by gluing 3 inch >> hexagons to a glass foam backer. The >> glass foam has the basic curve milled into it and the >> hexagons are worked >> like a block of lenses. >> >> The idea is to be able to make a mirror of very large size, >> say in the 2 >> meter range, without having to handle large chunks of >> glass. The idea came >> to me from looking at the Keck. Then I found a whole long >> discussion on >> the list dated June 2008. The list folks were talking >> active control. I >> said why not a monolithic structure. Well, they had argued >> it all out >> prior to this and were not interested for the most part. So >> I glued it up >> and I am grinding it. >> >> The picture is of a 18 inch F3 mirror. You can see a >> picture of the mirror >> in my upload section on the atm list. The picture was to >> show the >> strangeness of the polish. It is polishing from the middle >> out, which is >> normal, but the individual hexes are polishing from the >> edge in, which is >> weird. But it is polishing. I have about 7 hours into it >> now and I am >> making headway but it is like any mirror, slow and >> exacting. >> >> What more can I tell you? >> >> David Davis >> Toledo, OR 97391 >> >> >> >> >> >> > > > > From toolontop at yahoo.com Wed Jul 1 14:31:13 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Tue, 30 Jun 2009 22:31:13 -0700 (PDT) Subject: [ATM] Tessellated Mirror Picture Message-ID: <125231.71799.qm@web112414.mail.gq1.yahoo.com> My thinking is that if the polisher is large enough it won't damage the support foam, but I don't actually know how resilient the foam is. I think I would avoid cold pressing altogether on something like this, as brief hot pressing works a wonder. But figuring an f/3 is something else again, and though Mel knows how to do it with an oversize lap I certainly don't! I understand you're using RTV to adhere the tessellations to the backing? Something nonflexible might be a better choice, though I realize this is a test to see if it works at all. The idea with the oversized polisher is you don't really have to move off it to bring it spherical, at least. Shorter strokes will do it, but pressing for contact takes some care. Again, I've not tried this at f/3. Best, Mark --- On Tue, 6/30/09, vorblesnak at peak.org wrote: > From: vorblesnak at peak.org > Subject: Re: Tessellated Mirror Picture > To: "Mark Cowan" > Cc: vorblesnak at peak.org, atm at atmlist.net > Date: Tuesday, June 30, 2009, 3:26 PM > A couple of folks have suggested > either an oversized lap or a full sized > lap to finish the polishing work. The mirror is probably > about 17 inches > across. I am using a 12 inch lap. Anyone care to specify a > size and a why? > I am willing to make that move if it will bring this thing > to polish and > figure. > > I was thinking earlier, there had been some concern > expressed about > crushing the glass foam slightly as polishing progressed. > This would have > the affect of changing the curve with every polishing > cycle. I usually > cold press at the end of a polishing day adding a lead > ring, (about 25 > pounds), to the top of the stack. I began to wonder if that > might also > damage the glass foam curve. > > David Davis > Toledo, OR 97391 > > > From richard1941 at gmail.com Wed Jul 1 15:10:14 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Wed, 1 Jul 2009 01:10:14 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4AC16B.9090609@inreach.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <4A4ABE80.3050206@gmail.com> <4A4AC16B.9090609@inreach.com> Message-ID: Note that the Hubble mirror works in a tough thermal environment with no convection to equalize temperature. Instead of a heat conductor (which never completely equalizes) the used zerodur. 1970's technology, but hard to find fault with it. Sent from my iPhone On Jun 30, 2009, at 20:52, Jan Bentz wrote: > Mark Holm wrote: > >> Amateurs need to keep in mind that while aluminum has high thermal >> conductivity, the major deterrent to quick thermal equilibration in >> atm sized mirrors is the air boundary layer. Unless you are >> blowing the boundary layer away with fans, it won't matter much how >> good the thermal conductivity of the material is. I'm not making >> this up. Practical work by practical atm's has already proved it. >> >> Jan Bentz wrote: >> >>> >>> The main attraction of Al blanks is mainly the ease of >>> lightweighting and its outstanding "figure of merit". The last >>> has to do with a dimensionless number Andre Couder came up with >>> decades ago. It was a combination of thermal diffusivity, thermal >>> merit and specific stiffness. >>> I'm not sure how valid this is but Al ranked quite high on the >>> scale compared with other blank materials. >>> >>> Jan Bentz >>> _______________________________________________ >>> ATM mailing list http://www.atmlist.net/ >> >> >> > Mark -- Quite so but with its high conductivity the entire mirror > will reach equilibrium much faster than a glass one with or without > fans. > > -- Jan > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Wed Jul 1 15:50:47 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Wed, 1 Jul 2009 01:50:47 -0500 Subject: [ATM] Tessellated Mirror Picture In-Reply-To: <4A4A6B86.9010001@windstream.net> References: <471187.86863.qm@web112419.mail.gq1.yahoo.com> <4A4A6B86.9010001@windstream.net> Message-ID: <1DDE2AEA-57A2-4E2B-B513-B58760BBAEDB@gmail.com> How did you remove the coating ok the back? If by grinding, maybe the coating had nothing to do with it. Also, how did the glass look between crossed polorrhoids before you removed the back coating? (sorry, I'm just trying to keep you honest) Sent from my iPhone On Jun 30, 2009, at 14:46, waldo kitty wrote: > Mark Cowan wrote: >> I recently had a 14.7x.8" f/4.2 quartz mirror (finished!) gain 20% >> correction overall when I removed a slightly scratched sapphire >> coating from the bank of the blank! > > from the /back/ of the mirror? > > that would seem to indicate that it was causing the mirror to flex > and not be properly flat... interesting... very interesting... > > -- > _\/ > (@@) Waldo Kitty, Waldo's Place USA > __ooO_( )_Ooo_____________________ telnet://bbs.wpusa.dynip.com > _|_____|_____|_____|_____|_____|_____ http://www.wpusa.dynip.com > ____|_____|_____|_____|_____|_____|____ ftp://ftp.wpusa.dynip.com > _|_Eat_SPAM_to_email_me!_YUM!__|_____ wkitty42 -at- windstream.net > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Wed Jul 1 15:55:42 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Wed, 1 Jul 2009 01:55:42 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4A6046.4010701@inreach.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> Message-ID: <02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com> Can you provide a link to Couder's figure of merit? Sent from my iPhone On Jun 30, 2009, at 13:58, Jan Bentz wrote: > Michael Coslo wrote: > >> >> On Jun 27, 2009, at 5:34 PM, Mark Holm wrote: >> >>> I just don't understand why people keep thinking aluminum will >>> make lighter mirrors. Density is actually higher than glass and >>> modulus is only a bit higher. The two pretty much cancel each >>> other out. >>> Will a real mechanical or structural engineer address this? All >>> others, keep quiet. >> >> >> >> Okay, just let us know when us unwashed can join in..... ;^) Since >> I play a mechanical engineer on TV, I'll chime in. >> >> The reason that people keep bringing up Al is that it is cheap and >> potentially really easy to work with. >> >> If they include lightweight in the mix, they are kinda wrong - >> although it is disturbingly easy to honeycomb an Al mirror blank. >> Accurately following the front surface contour is not even that >> much more difficult, It' is almost irresistible for many people >> who like to make things to take a stab at an Al mirror. >> >> Problem is that Al has some other issues that make it not so >> desirable. Everyone who has tried to make an Al mirror knows them. >> >> I have no doubt that with enough time and money, good mirrors could >> be made from Al. I suspect that anything we come up with will no >> longer be cheap or easy, negating my first point above. >> >> >> -73 de Mike N3LI - >> >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > Mike -- You are certainly right in thinking it will take an > adventurous soul to try Al but there have been a couple of large > successful mirrors made of Al and many experiments mostly having to > do with the method of manufacture and treatment of the blank. > Casting, forging, rolling & welding have all been tried. The flats > or spheres figured on them have exibited various degrees of figure > change with time. Some methods are quite promising showing only a > small fraction of a fringe change while others will change several > fringes. It appears that the heat treatment they undergo vs. the > environment they will operate in is the most important factor. Many > of these experiments were done with an eye toward operation in > hostile environments so the blank preparation is not directly > applicable to our operating conditions. > The main attraction of Al blanks is mainly the ease of > lightweighting and its outstanding "figure of merit". The last has > to do with a dimensionless number Andre Couder came up with decades > ago. It was a combination of thermal diffusivity, thermal merit and > specific stiffness. > I'm not sure how valid this is but Al ranked quite high on the scale > compared with other blank materials. > > Jan Bentz > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From mjc5 at psu.edu Wed Jul 1 21:39:54 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Wed, 01 Jul 2009 08:39:54 -0400 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4ABE80.3050206@gmail.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <4A4ABE80.3050206@gmail.com> Message-ID: <1EF99455-58E1-4BB4-BB87-BA0BFC22906E@psu.edu> On Jun 30, 2009, at 9:40 PM, Mark Holm wrote: > Amateurs need to keep in mind that while aluminum has high thermal > conductivity, the major deterrent to quick thermal equilibration in > atm sized mirrors is the air boundary layer. Unless you are blowing > the boundary layer away with fans, it won't matter much how good the > thermal conductivity of the material is. I'm not making this up. > Practical work by practical atm's has already proved it. No doubt. A fan isn't a huge deal though. side note: My experiments with fans indicate that if you want lots of vibration, get an old computer fan or something at an electronics flea market, and run it nice and fast. You'll get those shaky images we all love. I did find that a nice unused brushless DC motor fan, run at a little less than rated voltage, will have virtually no vibration. And I say virtually because I can't believe something has no vibration - I couldn't detect any so take that for what it's worth. I ended up using a Radio Shack brushless fan rated at 12 volts, but run at 9 volts. I use 1 nine volt battery per observing session. Back to Al mirrors. I think the temperature issues will be the biggest problem for AL mirrors for our application. with that 23 linear/69 volume coefficient of expansion, the mirror is going to shake and dance a lot. For a fixed temperature application they would do a lot better. Steady hot or cold. So I think for astronomy, we'd be looking at: specialized grinding and polishing techniques (no big deal ) specialized coatings, unless we're planning to go through re-polishing old school like with speculum metal mirrors Question, does a nickel over Al coating give a bimetallic junction? Temperature stabilization - moving some fluid strikes me as the best way to keep a handle on temp variations. With the combination of high thermal conductivity/high coefficient of expansion, I think we want to acclimate quickly and as evenly as possible. That system sure complicates things a bit. -73 de Mike N3LI - From toolontop at yahoo.com Thu Jul 2 07:40:46 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Wed, 1 Jul 2009 15:40:46 -0700 (PDT) Subject: [ATM] sapphire coating was Tessellated Mirror Picture Message-ID: <66.99492.qm@web112402.mail.gq1.yahoo.com> Hi Richard, It wouldn't be a story worth relating if it wasn't unusual, now would it? If you take a finished thin mirror with a polished back and roughen it significantly with grinding, you increase the tension on the back of the mirror thanks to the Twymann effect. This causes the back to become very slightly concave and the front to go slightly convex, which manifests itself mostly around the edge as a depressed edge in testing. I've seen that happen before. Polishing it back restores the original figure to the front. In this case, the blank came with sapphire coatings on both side. One side was generated and worked as normal, until IIRC it tested finished. At that point I clean up the edges and back if needed, and due to some scratching on the back I elected to fine grind that by hand - but the grit wouldn't even touch it under hand pressure. I put it on the machine to go at either 320 or 500 SiC and finished with some AlOx around 25 micron to get a nice smooth surface. Normally that would have no appreciable effect on the figure. I put it on the test stand and it looked fine at first under Ronchi, but then I measured it and found 120% correction! Had to take it back and start over. Sorry, I don't recall exactly if the correction was the same zone-zone, but it looked very nice under Ronchi and, as I said, had tested finished before at 100% correction. I can only attribute it to the sapphire coating. I didn't test it for strain specifically, but I have an f/6.6 in process that has sapphire on the back and will be going into polishing - so I'll check it for strain before and after I take the coating off the back of that one (prior to figuring!!). Best, Mark --- On Tue, 6/30/09, Richard Schwartz wrote: > From: Richard Schwartz > Subject: Re: [ATM] Tessellated Mirror Picture > To: "wkitty42 at windstream.net" > Cc: "atm at atmlist.net" > Date: Tuesday, June 30, 2009, 11:50 PM > How did you remove the coating ok the > back?? If by grinding, maybe the coating had nothing to > do with it.? Also, how did the glass look between > crossed polorrhoids before you removed the back > coating?? (sorry, I'm just trying to keep you honest) > > Sent from my iPhone > > On Jun 30, 2009, at 14:46, waldo kitty > wrote: > > > Mark Cowan wrote: > >> I recently had a 14.7x.8" f/4.2 quartz mirror > (finished!) gain 20% correction overall when I removed a > slightly scratched sapphire coating from the bank of the > blank! > > > > from the /back/ of the mirror? > > > > that would seem to indicate that it was causing the > mirror to flex and not be properly flat... interesting... > very interesting... > > > > --? ? ? _\/ > >? ? ? (@@)? ? ? ? > ? ? ? ? ? ? ? Waldo > Kitty, Waldo's Place USA > > __ooO_( )_Ooo_____________________ > telnet://bbs.wpusa.dynip.com > > _|_____|_____|_____|_____|_____|_____ http://www.wpusa.dynip.com > > ____|_____|_____|_____|_____|_____|____ ftp://ftp.wpusa.dynip.com > > _|_Eat_SPAM_to_email_me!_YUM!__|_____ wkitty42 -at- > windstream.net > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From jbentz at inreach.com Thu Jul 2 11:24:52 2009 From: jbentz at inreach.com (Jan Bentz) Date: Wed, 01 Jul 2009 19:24:52 -0700 Subject: [ATM] large aluminum mirrors In-Reply-To: <02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com> Message-ID: <4A4C1A74.3060602@inreach.com> Richard wrote: Can you provide a link to Couder's figure of merit? Richard -- I found it in Wilson RTO II starting on p. 216. The original reference is Couder, A,1931, Bulletin Astronomique, 2me Serie, Tome VII, Fasc. VI, 201 . A later reference is Maksutov,D.D., 1954 "Technologie der Astronomischen Optic", VEB Verlag Technik, Berlin, 22 Basically Couder proposed a thermal criteria while Maksutov included a more complete mechanical factor in the same equation. Figure of merit = thermal conductivity / expansion coefficient x specific heat x density. Maksutovs contribution was to multiply this whole thing by Young's modulus. There are materials that are higher on this scale than Al but are disqualified as impractical for amateurs like berylium or silicon carbide. Jan Bentz From jbentz at inreach.com Thu Jul 2 11:39:31 2009 From: jbentz at inreach.com (Jan Bentz) Date: Wed, 01 Jul 2009 19:39:31 -0700 Subject: [ATM] large aluminum mirrors In-Reply-To: <1EF99455-58E1-4BB4-BB87-BA0BFC22906E@psu.edu> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <4A4ABE80.3050206@gmail.com> <1EF99455-58E1-4BB4-BB87-BA0BFC22906E@psu.edu> Message-ID: <4A4C1DE3.304@inreach.com> Michael Coslo wrote: > > On Jun 30, 2009, at 9:40 PM, Mark Holm wrote: > >> Amateurs need to keep in mind that while aluminum has high thermal >> conductivity, the major deterrent to quick thermal equilibration in >> atm sized mirrors is the air boundary layer. Unless you are blowing >> the boundary layer away with fans, it won't matter much how good the >> thermal conductivity of the material is. I'm not making this up. >> Practical work by practical atm's has already proved it. > > > > No doubt. A fan isn't a huge deal though. > > side note: My experiments with fans indicate that if you want lots of > vibration, get an old computer fan or something at an electronics > flea market, and run it nice and fast. You'll get those shaky images > we all love. I did find that a nice unused brushless DC motor fan, > run at a little less than rated voltage, will have virtually no > vibration. And I say virtually because I can't believe something has > no vibration - I couldn't detect any so take that for what it's > worth. I ended up using a Radio Shack brushless fan rated at 12 > volts, but run at 9 volts. I use 1 nine volt battery per observing > session. > > Back to Al mirrors. > > I think the temperature issues will be the biggest problem for AL > mirrors for our application. with that 23 linear/69 volume > coefficient of expansion, the mirror is going to shake and dance a lot. > > For a fixed temperature application they would do a lot better. > Steady hot or cold. > > So I think for astronomy, we'd be looking at: > > specialized grinding and polishing techniques (no big deal ) > > specialized coatings, unless we're planning to go through > re-polishing old school like with speculum metal mirrors > Question, does a nickel over Al coating give a bimetallic junction? > > Temperature stabilization - moving some fluid strikes me as the best > way to keep a handle on temp variations. With the combination of high > thermal conductivity/high coefficient of expansion, I think we want > to acclimate quickly and as evenly as possible. That system sure > complicates things a bit. > > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > Mike -- Some of the large mirrors of Al have a fluid solution flowing through cavities or pipes inside the body of the mirror. They reach equilibrium much faster and maintain a constant temp much better than anything you could do with just fans. The nickel coating is for ease of grinding and polishing and is overcoated with evaporated Al just like glass but there is some suspicion that it may cause a slight figure change because of unequal expansion rates with the Al Jan Bentz. From richard at foucault.co.uk Thu Jul 2 19:13:09 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Thu, 2 Jul 2009 11:13:09 +0100 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4C1A74.3060602@inreach.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com> <4A4C1A74.3060602@inreach.com> Message-ID: <1687222259.20090702111309@foucault.co.uk> Hello Jan, Thursday, July 2, 2009, 3:24:52 AM, you wrote: > There are materials that are higher on this scale than Al but are > disqualified as impractical for amateurs like berylium or silicon carbide. I would think the AlSic group of materials would fair well, with typical figures 190W/mK, 8ppm/C and 3g/cm3. Maybe we need to multiply by an ease of manufacture constant though. -- Best regards, Richard in the UK From atmer at flash.net Thu Jul 2 20:37:07 2009 From: atmer at flash.net (Anthony Stillman) Date: Thu, 2 Jul 2009 04:37:07 -0700 (PDT) Subject: [ATM] large aluminum mirrors Message-ID: <271773.76568.qm@web82003.mail.mud.yahoo.com> > There are materials that are higher on this scale than Al > but are disqualified as impractical for amateurs like > berylium or silicon carbide. Disqualified? Impractical? What! has happened to the ATM spirit? Sure moissanite is hard as hell and ridiculously expensive, shrink the instrument. Yea beryllium dust is deadly poison but with great care and olive oil it's manageable. Not huge is OK. An ultra light weight liquid cooled titanium mirror single digit inches in diameter is still cool. Anthony From mjc5 at psu.edu Thu Jul 2 21:53:29 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Thu, 02 Jul 2009 08:53:29 -0400 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4C1DE3.304@inreach.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <4A4ABE80.3050206@gmail.com> <1EF99455-58E1-4BB4-BB87-BA0BFC22906E@psu.edu> <4A4C1DE3.304@inreach.com> Message-ID: On Jul 1, 2009, at 10:39 PM, Jan Bentz wrote: >> >> >> specialized coatings, unless we're planning to go through re- >> polishing old school like with speculum metal mirrors >> Question, does a nickel over Al coating give a bimetallic >> junction? >> >> Temperature stabilization - moving some fluid strikes me as the >> best way to keep a handle on temp variations. With the combination >> of high thermal conductivity/high coefficient of expansion, I >> think we want to acclimate quickly and as evenly as possible. That >> system sure complicates things a bit. >> >> >> -73 de Mike N3LI - >> >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > Mike -- Some of the large mirrors of Al have a fluid solution > flowing through cavities or pipes inside the body of the mirror. > They reach equilibrium much faster and maintain a constant temp > much better than anything you could do with just fans. The nickel > coating is for ease of grinding and polishing and is overcoated with > evaporated Al just like glass but there is some suspicion that it > may cause a slight figure change because of unequal expansion rates > with the Al hmmm, maybe someone could do bimetallic stressing to do the final figure on a mirror? 8^) No doubt that the liquid based thermal control system would be good, just a lot of extra work, esp if we opt for lightweight honeycombing of the mirror. -73 de Mike N3LI - From stainless_steel at suddenlink.net Thu Jul 2 22:42:03 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 2 Jul 2009 08:42:03 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4C1A74.3060602@inreach.com> References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd><4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com> <4A4C1A74.3060602@inreach.com> Message-ID: <41215EF3B976482B977C6120FB05FA74@R101> Has anyone thought about the old standby, "speculum metal" for mirrors, as Herschel and others in the 18th century had so much success with? D-LZ130 ----- Original Message ----- From: "Jan Bentz" To: "Richard Schwartz" ; "ATM List" Sent: Wednesday, July 01, 2009 9:24 PM Subject: Re: [ATM] large aluminum mirrors > Richard wrote: > Can you provide a link to Couder's figure of merit? > > Richard -- I found it in Wilson RTO II starting on p. 216. The original > reference is Couder, A,1931, Bulletin Astronomique, 2me Serie, Tome > VII, Fasc. VI, 201 . A later reference is Maksutov,D.D., 1954 > "Technologie der Astronomischen Optic", VEB Verlag Technik, Berlin, 22 > > Basically Couder proposed a thermal criteria while Maksutov included a > more complete mechanical factor in the same equation. Figure of merit > = thermal conductivity / expansion coefficient x specific heat x > density. Maksutovs contribution was to multiply this whole thing by > Young's modulus. > > There are materials that are higher on this scale than Al but are > disqualified as impractical for amateurs like berylium or silicon carbide. > > Jan Bentz > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2213 - Release Date: 07/01/09 18:07:00 From stainless_steel at suddenlink.net Thu Jul 2 22:53:44 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 2 Jul 2009 08:53:44 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: <1687222259.20090702111309@foucault.co.uk> References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd><4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <1687222259.20090702111309@foucault.co.uk> Message-ID: <2BDFE76399EB422C88BA0E8387F52DF6@R101> Berylium is dangerous. It used to be used in flourescent (early) light rods, but was abandoned when found to be deadly. It is used for little else now. Why not try "speculum metal"?- as was the universal mirror material until Foucault tried glass, with silver on front. Speculum metal worked for the Herschels and Lord Rosse, and many others; they had litttle to complain about its performance. Today, we would coat the functional side with something to raise the reflectivity. A suggestion for those who are looking for an alternative material, for the fun of it, and the novelty of it. Speculum metal is more dimensionally stable during temperature changes than aluminum. Aluminum is wonderful for the framework of ultra large "rigid" airships. One ultra large airship had an unbreakable hull, with no wire bracing in its novel main frame rings, which were made of STAINLESS STEEL! The bureacrats in charge of the engineers killed the ship, though. Macon and Akron were predicted to fail structurally where their fins were attached, by their designer. They fulfilled his predictions; they also had non wire braced deep cross section cantilever main frame rings and their hulls were also unbreakable, but they were the only ships that did not carry the mainspars of the fins through the hull. This is where they failed structurally. Davey ----- Original Message ----- From: "Richard in the UK" To: "Jan Bentz" Sent: Thursday, July 02, 2009 5:13 AM Subject: Re: [ATM] large aluminum mirrors > Hello Jan, > > Thursday, July 2, 2009, 3:24:52 AM, you wrote: > >> There are materials that are higher on this scale than Al but are >> disqualified as impractical for amateurs like berylium or silicon >> carbide. > > I would think the AlSic group of materials would fair well, with > typical figures 190W/mK, 8ppm/C and 3g/cm3. Maybe we need to multiply > by an ease of manufacture constant though. > > -- > Best regards, > Richard in the UK > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2213 - Release Date: 07/01/09 18:07:00 From mjc5 at psu.edu Thu Jul 2 23:01:47 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Thu, 02 Jul 2009 10:01:47 -0400 Subject: [ATM] large aluminum mirrors In-Reply-To: <41215EF3B976482B977C6120FB05FA74@R101> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com> <4A4C1A74.3060602@inreach.com> <41215EF3B976482B977C6120FB05FA74@R101> Message-ID: On Jul 2, 2009, at 9:42 AM, wrote: > Has anyone thought about the old standby, "speculum metal" for > mirrors, as Herschel and others in the 18th century had so much > success with? I've speculumated about it...... (cymbal crash) -73 de Mike N3LI - From mjc5 at psu.edu Thu Jul 2 23:10:47 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Thu, 02 Jul 2009 10:10:47 -0400 Subject: [ATM] large aluminum mirrors In-Reply-To: <2BDFE76399EB422C88BA0E8387F52DF6@R101> References: <543577.83904.qm@web81902.mail.mud.yahoo.com> <001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com> <6982D539-0017-47C7-B018-17AE17A23340@psu.edu> <4A4A6046.4010701@inreach.com> <02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com> <4A4C1A74.3060602@inreach.com> <1687222259.20090702111309@foucault.co.uk> <2BDFE76399EB422C88BA0E8387F52DF6@R101> Message-ID: <1DAB1FC3-6184-4C4B-B959-44DDD16EFF02@psu.edu> On Jul 2, 2009, at 9:53 AM, wrote: > Berylium is dangerous. It used to be used in flourescent (early) > light rods, but was abandoned when found to be deadly. It is used > for little else now. Agreed, Be is Bad. I'm not afraid of much, but that is one of the things I wouldn't work with. > Why not try "speculum metal"?- as was the universal mirror material > until Foucault tried glass, with silver on front. Speculum metal > worked for the Herschels and Lord Rosse, and many others; they had > litttle to complain about its performance. Today, we would coat the > functional side with something to raise the reflectivity. Not a bad idea, Davey. The resourceful ATM'er could take the mirror the whole way through the process, from casting to finishing. A coating would take care of the major issue of speculum metal, the reflectance. I like it! -73 de Mike N3LI - From junkwheaton at gmail.com Fri Jul 3 03:33:08 2009 From: junkwheaton at gmail.com (Bill Wheaton) Date: Thu, 2 Jul 2009 14:33:08 -0400 Subject: [ATM] Cement tile tool design In-Reply-To: References: Message-ID: Paul Check out my blog in the archives. Plenty of pictures and descriptions of my latest... using Davey's method. Sweet! No gooey epoxy. http://pythiashat.blogspot.com -Bill On Mon, Jun 22, 2009 at 2:11 PM, Paul Kulyk wrote: > I am considering making a cement tile tool. What is the general > consensus on pouring the cement directly onto the tiles? Is it a > better idea to epoxy them on top of a hardened disk? > > Thanks, > Paul > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From leftfieldstar at aol.com Fri Jul 3 03:35:49 2009 From: leftfieldstar at aol.com (leftfieldstar at aol.com) Date: Thu, 02 Jul 2009 14:35:49 -0400 Subject: [ATM] Coma and Mirror size In-Reply-To: <1508.69.59.200.230.1246334403.squirrel@webmail.peak.org> References: <1508.69.59.200.230.1246334403.squirrel@webmail.peak.org> Message-ID: <8CBC95B0E3CD1EB-1680-AED@WEBMAIL-DY39.sysops.aol.com> Quoted from another list: "I have verified that field curvature in Newtonian depends only on the focal length. As the focal length is longer, the field curvature is less. Coma depends on the F/# and aperture. Bigger the aperture at the same F/#, less coma and it is due to the mirror being less curved in a larger mirror. Hence the eyepiece may look sharper off-axis because the field is flatter. (if the eyepiece is designed for flat field first). " Is there a false statement in there? Is the author unaware of probable vignetting at the eyepiece on larger mirrors he has observed through? Dominic Di Leo From stainless_steel at suddenlink.net Fri Jul 3 08:41:00 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 2 Jul 2009 18:41:00 -0500 Subject: [ATM] Cement tile tool design In-Reply-To: References: Message-ID: <09772EEE607B47DDBA8374AABBB32F8A@R101> http://www.atmsite.org/contrib/Harbour/Tool.html ----- Original Message ----- From: "Bill Wheaton" To: "Paul Kulyk" Cc: Sent: Thursday, July 02, 2009 1:33 PM Subject: Re: [ATM] Cement tile tool design > Paul > Check out my blog in the archives. Plenty of pictures and descriptions of > my latest... using Davey's method. Sweet! No gooey epoxy. > http://pythiashat.blogspot.com > -Bill > > On Mon, Jun 22, 2009 at 2:11 PM, Paul Kulyk wrote: > >> I am considering making a cement tile tool. What is the general >> consensus on pouring the cement directly onto the tiles? Is it a >> better idea to epoxy them on top of a hardened disk? >> >> Thanks, >> Paul >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2215 - Release Date: 07/02/09 18:06:00 From stainless_steel at suddenlink.net Fri Jul 3 08:44:54 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 2 Jul 2009 18:44:54 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: <1DAB1FC3-6184-4C4B-B959-44DDD16EFF02@psu.edu> References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com><4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com><1687222259.20090702111309@foucault.co.uk><2BDFE76399EB422C88BA0E8387F52DF6@R101> <1DAB1FC3-6184-4C4B-B959-44DDD16EFF02@psu.edu> Message-ID: Thank you, Mike. "Sometimes the way forward is the way back" From what movie, starring a beauty who appeared in "A Beautiful Mind", but much, much earlier. Name the movie, win magic card trick. Davey ----- Original Message ----- From: "Michael Coslo" To: "ATM List" Sent: Thursday, July 02, 2009 9:10 AM Subject: Re: [ATM] large aluminum mirrors > > On Jul 2, 2009, at 9:53 AM, wrote: > >> Berylium is dangerous. It used to be used in flourescent (early) >> light rods, but was abandoned when found to be deadly. It is used >> for little else now. > > Agreed, Be is Bad. I'm not afraid of much, but that is one of the > things I wouldn't work with. > > > >> Why not try "speculum metal"?- as was the universal mirror material >> until Foucault tried glass, with silver on front. Speculum metal >> worked for the Herschels and Lord Rosse, and many others; they had >> litttle to complain about its performance. Today, we would coat the >> functional side with something to raise the reflectivity. > > Not a bad idea, Davey. The resourceful ATM'er could take the mirror > the whole way through the process, from casting to finishing. A > coating would take care of the major issue of speculum metal, the > reflectance. I like it! > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2215 - Release Date: 07/02/09 18:06:00 From stainless_steel at suddenlink.net Fri Jul 3 08:47:19 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 2 Jul 2009 18:47:19 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com><4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <41215EF3B976482B977C6120FB05FA74@R101> Message-ID: Knowing you, I was sure that you had thought of it. D-LZ130 (Do it, Mike- show us how well it will work. Surely a silver coating on such a metal disk will not alter the mnetal substrate's properties in any significant way.) ----- Original Message ----- From: "Michael Coslo" To: "ATM List" Sent: Thursday, July 02, 2009 9:01 AM Subject: Re: [ATM] large aluminum mirrors > > On Jul 2, 2009, at 9:42 AM, wrote: > >> Has anyone thought about the old standby, "speculum metal" for >> mirrors, as Herschel and others in the 18th century had so much >> success with? > > > I've speculumated about it...... > > (cymbal crash) > > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2215 - Release Date: 07/02/09 18:06:00 From wkitty42 at windstream.net Fri Jul 3 09:35:32 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Thu, 02 Jul 2009 20:35:32 -0400 Subject: [ATM] large aluminum mirrors In-Reply-To: References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com><4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <41215EF3B976482B977C6120FB05FA74@R101> Message-ID: <4A4D5254.8040509@windstream.net> stainless_steel at suddenlink.net wrote: > Knowing you, I was sure that you had thought of it. > > D-LZ130 > > (Do it, Mike- show us how well it will work. Surely a silver coating on > such a metal disk will not alter the mnetal substrate's properties in > any significant way.) i can only imagine the bi-metalic properties that might be presented with a tin/copper base coated with a silver or aluminum coating ;) From richard1941 at gmail.com Fri Jul 3 13:22:58 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Thu, 2 Jul 2009 21:22:58 -0700 Subject: [ATM] large aluminum mirrors In-Reply-To: References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com><4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com><1687222259.20090702111309@foucault.co.uk><2BDFE76399EB422C88BA0E8387F52DF6@R101> <1DAB1FC3-6184-4C4B-B959-44DDD16EFF02@psu.edu> Message-ID: In my book case I found "compAct algorithms for numerical computers". Good stuff, not at all insane. By John Nash. Sent from my iPhone On Jul 2, 2009, at 16:44, wrote: > Thank you, Mike. > > "Sometimes the way forward is the way back" From what movie, > starring a beauty who appeared in "A Beautiful Mind", but much, much > earlier. Name the movie, win magic card trick. > > Davey > > > ----- Original Message ----- From: "Michael Coslo" > To: "ATM List" > Sent: Thursday, July 02, 2009 9:10 AM > Subject: Re: [ATM] large aluminum mirrors > > >> >> On Jul 2, 2009, at 9:53 AM, wrote: >> >>> Berylium is dangerous. It used to be used in flourescent (early) >>> light rods, but was abandoned when found to be deadly. It is used >>> for little else now. >> >> Agreed, Be is Bad. I'm not afraid of much, but that is one of the >> things I wouldn't work with. >> >> >> >>> Why not try "speculum metal"?- as was the universal mirror material >>> until Foucault tried glass, with silver on front. Speculum metal >>> worked for the Herschels and Lord Rosse, and many others; they had >>> litttle to complain about its performance. Today, we would coat the >>> functional side with something to raise the reflectivity. >> >> Not a bad idea, Davey. The resourceful ATM'er could take the mirror >> the whole way through the process, from casting to finishing. A >> coating would take care of the major issue of speculum metal, the >> reflectance. I like it! >> -73 de Mike N3LI - >> >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > > --- > --- > --- > --- > -------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.375 / Virus Database: 270.13.2/2215 - Release Date: 07/02/09 18 > :06:00 > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From b-hamburger at artinso.com Fri Jul 3 16:54:53 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Fri, 3 Jul 2009 09:54:53 +0200 Subject: [ATM] Coma and Mirror size In-Reply-To: <8CBC95B0E3CD1EB-1680-AED@WEBMAIL-DY39.sysops.aol.com> References: <1508.69.59.200.230.1246334403.squirrel@webmail.peak.org> <8CBC95B0E3CD1EB-1680-AED@WEBMAIL-DY39.sysops.aol.com> Message-ID: <022801c9fbb3$8e5df5d0$ab19e170$@com> The F number defines the ratio between the diameter of an optical element and its focal length as we all know, the focal length being 1/2 of ROC. If we take an example: let's say a 100mm F6 mirror will have a ROC of 1200mm, a 150mm with the same ROC (same curvature) will be F4 and a 300mm mirror with the same ROC (same curvature) will be F2. Intuitively we will all agree that the 100mm mirror will most likely suffer very little of COMA, while the other two will exhibit progressive COMA as off-axis aberration. That shows that it is not the curvature of the optical element itself that defines whether coma is present or not, but rather the DIAMETER of the optical element for a given curvature. That becomes clear if we examine the Abbe sin condition (telescope optics p.28) which shows that it is the height of a parallel ray at the entrance pupil in relation to the axis of the optical element that defines whether it fulfils that condition or not. To resume: -Considering that the F number defines a relation between a given curvature and the diameter of an optical element it becomes clear that any F4 element will exhibit same grade of COMA irrespective whether it has big or small diameter. -It is not so much the curvature that defines strength of COMA, but the diameter for a given curvature Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of leftfieldstar at aol.com > Sent: jueves, 02 de julio de 2009 20:36 > To: atm at atmlist.net > Subject: [ATM] Coma and Mirror size > > Quoted from another list: > > "I have verified that field curvature in Newtonian depends only on the > focal length. As the focal length is longer, the field curvature is > less. Coma depends on the F/# and aperture. Bigger the aperture at the > same F/#, less coma and it is due to the mirror being less curved in a > larger mirror. Hence the eyepiece may look sharper off-axis because the > field is flatter. (if the eyepiece is designed for flat field first). " > > Is there a false statement in there? Is the author unaware of probable > vignetting at the eyepiece on larger mirrors he has observed through? > > Dominic Di Leo > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From brian.itsi at gmail.com Fri Jul 3 18:25:23 2009 From: brian.itsi at gmail.com (Brian Karlsen) Date: Fri, 3 Jul 2009 11:25:23 +0200 Subject: [ATM] refractor clarification Message-ID: <7b48d05a0907030225i771bc396s502684fe7cbc6d1a@mail.gmail.com> Hi all I just joined the list and am looking forward to learning much more about this interesting hobby. I am in the process of designing and sourcing the components for my first non department store "aka toy" and would like to check my thinking before I start purchasing. the plan is for a simple refractor 2 convex lenses mounted in a piece of PVC pipe the lenses I am looking at are from http://www.surplusshed.com/ For the primary lens I am looking at the L10238 lens 83mm diameter 550mm fl for the eyepiece lens I plan on using the L3993 22mm diameter 18mm fl from what I understand these should be spaced proximately fl 1+fl 2= 550+18=568mm apart and will give a magnification of fl 1 / fl 2= 550/18= 30.5x are all these calculations correct, am I mising anything, would this work, I am also going to make it so the distance betweel the lens is adjustable an inch or 2 for focus any sugestions. thanks in anticipation of youre responces. Brian From stainless_steel at suddenlink.net Fri Jul 3 21:33:48 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Fri, 3 Jul 2009 07:33:48 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4D5254.8040509@windstream.net> References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd> <4A4685AF.7050002@inreach.com><4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <41215EF3B976482B977C6120FB05FA74@R101> <4A4D5254.8040509@windstream.net> Message-ID: <633F24E29F254FB5B3EFB6C895ECA748@R101> Coating would surely be too thin to contribute to any bimetallic properties. Kanigan did not hurt the Italian 70 aluminum mirror (70's) ----- Original Message ----- From: "waldo kitty" To: "ATM List" Sent: Thursday, July 02, 2009 7:35 PM Subject: Re: [ATM] large aluminum mirrors > stainless_steel at suddenlink.net wrote: >> Knowing you, I was sure that you had thought of it. >> >> D-LZ130 >> >> (Do it, Mike- show us how well it will work. Surely a silver coating on >> such a metal disk will not alter the mnetal substrate's properties in >> any significant way.) > > i can only imagine the bi-metalic properties that might be presented with > a > tin/copper base coated with a silver or aluminum coating ;) > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2215 - Release Date: 07/02/09 18:06:00 From stainless_steel at suddenlink.net Fri Jul 3 21:37:06 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Fri, 3 Jul 2009 07:37:06 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd><4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <1687222259.20090702111309@foucault.co.uk> <2BDFE76399EB422C88BA0E8387F52DF6@R101> Message-ID: It was used in the Gemini and Mercury heat shields, so you must be right. Read: "Sucker Bait" by Isaac Asimov. One of his better stories. Is about the danger of Beryllium, in a fictional setting. D-LZ130 ----- Original Message ----- From: "Richard Schwartz" To: Sent: Thursday, July 02, 2009 6:37 PM Subject: Re: [ATM] large aluminum mirrors > Beryliam is good stuff for aircraft brake drums and other heat > absorbers, and is cheaper than the other good heat conductor (diamond). > > Sent from my iPhone > > On Jul 2, 2009, at 6:53, wrote: > >> Berylium is dangerous. It used to be used in flourescent (early) >> light rods, but was abandoned when found to be deadly. It is used >> for little else now. >> >> Why not try "speculum metal"?- as was the universal mirror material >> until Foucault tried glass, with silver on front. Speculum metal >> worked for the Herschels and Lord Rosse, and many others; they had >> litttle to complain about its performance. Today, we would coat the >> functional side with something to raise the reflectivity. >> >> A suggestion for those who are looking for an alternative material, >> for the fun of it, and the novelty of it. Speculum metal is more >> dimensionally stable during temperature changes than aluminum. >> Aluminum is wonderful for the framework of ultra large "rigid" >> airships. One ultra large airship had an unbreakable hull, with no >> wire bracing in its novel main frame rings, which were made of >> STAINLESS STEEL! The bureacrats in charge of the engineers killed >> the ship, though. Macon and Akron were predicted to fail >> structurally where their fins were attached, by their designer. They >> fulfilled his predictions; they also had non wire braced deep cross >> section cantilever main frame rings and their hulls were also >> unbreakable, but they were the only ships that did not carry the >> mainspars of the fins through the hull. This is where they failed >> structurally. >> >> Davey >> >> >> ----- Original Message ----- From: "Richard in the UK" >> > > >> To: "Jan Bentz" >> Sent: Thursday, July 02, 2009 5:13 AM >> Subject: Re: [ATM] large aluminum mirrors >> >> >>> Hello Jan, >>> >>> Thursday, July 2, 2009, 3:24:52 AM, you wrote: >>> >>>> There are materials that are higher on this scale than Al but are >>>> disqualified as impractical for amateurs like berylium or silicon >>>> carbide. >>> >>> I would think the AlSic group of materials would fair well, with >>> typical figures 190W/mK, 8ppm/C and 3g/cm3. Maybe we need to multiply >>> by an ease of manufacture constant though. >>> >>> -- >>> Best regards, >>> Richard in the UK >>> >>> _______________________________________________ >>> ATM mailing list http://www.atmlist.net/ >> >> >> --- >> --- >> --- >> --- >> -------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 8.5.375 / Virus Database: 270.13.2/2213 - Release Date: 07/01/09 >> 18 >> :07:00 >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2215 - Release Date: 07/02/09 18:06:00 From stainless_steel at suddenlink.net Fri Jul 3 21:59:01 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Fri, 3 Jul 2009 07:59:01 -0500 Subject: [ATM] Coma and Mirror size In-Reply-To: <022801c9fbb3$8e5df5d0$ab19e170$@com> References: <1508.69.59.200.230.1246334403.squirrel@webmail.peak.org><8CBC95B0E3CD1EB-1680-AED@WEBMAIL-DY39.sysops.aol.com> <022801c9fbb3$8e5df5d0$ab19e170$@com> Message-ID: <89D0BB1F5BEC41CCA24C6AE2C7712697@R101> F ratio defines amount of coma. F ratio exclusively (for mirrors) D-LZ130 ----- Original Message ----- From: "Berthold Hamburger" To: Cc: Sent: Friday, July 03, 2009 2:54 AM Subject: Re: [ATM] Coma and Mirror size > The F number defines the ratio between the diameter of an optical element > and its focal length as we all know, the focal length being 1/2 of ROC. > > If we take an example: let's say a 100mm F6 mirror will have a ROC of > 1200mm, a 150mm with the same ROC (same curvature) will be F4 and a 300mm > mirror with the same ROC (same curvature) will be F2. Intuitively we will > all agree that the 100mm mirror will most likely suffer very little of > COMA, > while the other two will exhibit progressive COMA as off-axis aberration. > That shows that it is not the curvature of the optical element itself that > defines whether coma is present or not, but rather the DIAMETER of the > optical element for a given curvature. > > That becomes clear if we examine the Abbe sin condition (telescope optics > p.28) which shows that it is the height of a parallel ray at the entrance > pupil in relation to the axis of the optical element that defines whether > it > fulfils that condition or not. > > To resume: > -Considering that the F number defines a relation between a given > curvature > and the diameter of an optical element it becomes clear that any F4 > element > will exhibit same grade of COMA irrespective whether it has big or small > diameter. > -It is not so much the curvature that defines strength of COMA, but the > diameter for a given curvature > > Berthold > > -- > Berthold Hamburger - Cellist/Spain > Email: behambu at artinso.com > http://www.artinso.com > http://www.astro.artinso.com > > >> -----Original Message----- >> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf >> Of leftfieldstar at aol.com >> Sent: jueves, 02 de julio de 2009 20:36 >> To: atm at atmlist.net >> Subject: [ATM] Coma and Mirror size >> >> Quoted from another list: >> >> "I have verified that field curvature in Newtonian depends only on the >> focal length. As the focal length is longer, the field curvature is >> less. Coma depends on the F/# and aperture. Bigger the aperture at the >> same F/#, less coma and it is due to the mirror being less curved in a >> larger mirror. Hence the eyepiece may look sharper off-axis because the >> field is flatter. (if the eyepiece is designed for flat field first). " >> >> Is there a false statement in there? Is the author unaware of probable >> vignetting at the eyepiece on larger mirrors he has observed through? >> >> Dominic Di Leo >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.2/2215 - Release Date: 07/02/09 18:06:00 From thomas at moiler.com Fri Jul 3 22:07:20 2009 From: thomas at moiler.com (Thomas Janstrom) Date: Fri, 3 Jul 2009 23:07:20 +1000 Subject: [ATM] Slightly OT: Pictures from my US trip to date: Some stuff is ATM related. Message-ID: <027901c9fbdf$34a5f520$9df1df60$@com> Hi All, Just thought I'd share some pictures from my wanderings around the US, I'm now two months into the trip and I'm getting a bit travel weary. http://www.pbase.com/praxis178/us_gallery clicking on the pictures will bring up the original size image, those with ::text:: are links to sub galleries. In the hobbies one you will find some work I did to help advance the foam mirror project and help out Andrew with his monster vacuum chamber. The rest of the photos are just holiday snaps. Enjoy. Cheers, Thomas Janstrom. Little Gems. http://tjlittlegems.com From foreilly at bestweb.net Sat Jul 4 03:22:43 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Fri, 3 Jul 2009 14:22:43 -0400 Subject: [ATM] Videos Message-ID: <8DE63C26CE0242F790022C667C61CAEA@D5GHLR11> I have posted a series of videos on polishing optical flats on YouTube. If you are interested, they may be found at: http://www.youtube.com/user/foreilly1958 Click the Video Link in the upper left area of the web page. Ignore the Carrizozo Cider and Deep Woods Off reviews, they were posted in a silly minute, mostly for my kids to see. Best regards to all for a Great Fourth of July! Francis J. O'Reilly From vla at copper.net Sat Jul 4 04:09:14 2009 From: vla at copper.net (vladimir sacek) Date: Fri, 3 Jul 2009 15:09:14 -0400 Subject: [ATM] Coma and Mirror size References: <1508.69.59.200.230.1246334403.squirrel@webmail.peak.org> <8CBC95B0E3CD1EB-1680-AED@WEBMAIL-DY39.sysops.aol.com> Message-ID: <002201c9fc11$c2cf2a10$1d58f804@Handsome> Primary coma (the form significant in amateurs' mirrors) is described with two simple relations. One is the length of geometric blur (ray spot, tangential coma) B=3h/16F^2 where "h" is the linear height in the image space, and the other is the wavefront error, P-V=h/48F^3 and RMS=P-V/sq.rt.32. For given relative magnification (in units of the aperture), and assuming constant eyepiece AFOV, coma doesn't change with the aperture. But for given nominal magnification, it will be proportionally lower in smaller aperture, because of the linear height in the image space for given TFOV being also proportionally smaller (i.e. assuming 50-degree ep and 100x magnification, both smaller and larger telescope have identical TFOV of half a degree, but the linear field diameter is proportionally larger in the latter due to its longer f.l.). Field curvature is of little consequence for either visual or photo. For visual due to eye accommodation, and for photo-detector due to the coma error farther out in the field being much larger than the defocus error created by only moderately curved best image surface. How the errors of the eyepiece will combine with those of the mirror is a different subject. It is pretty much unpredictable, since ep manufacturers don't publish data on ep aberrations. Vla ----- Original Message ----- From: To: Sent: Thursday, July 02, 2009 2:35 PM Subject: [ATM] Coma and Mirror size > Quoted from another list: > > "I have verified that field curvature in Newtonian depends only on the > focal length. As the focal length is longer, the field curvature is less. > Coma depends on the F/# and aperture. Bigger the aperture at the same F/#, > less coma and it is due to the mirror being less curved in a larger > mirror. Hence the eyepiece may look sharper off-axis because the field is > flatter. (if the eyepiece is designed for flat field first). " > > Is there a false statement in there? Is the author unaware of probable > vignetting at the eyepiece on larger mirrors he has observed through? > > Dominic Di Leo > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From rmay at nethere.com Sat Jul 4 05:28:05 2009 From: rmay at nethere.com (Bob May) Date: Fri, 3 Jul 2009 13:28:05 -0700 Subject: [ATM] refractor clarification References: <7b48d05a0907030225i771bc396s502684fe7cbc6d1a@mail.gmail.com> Message-ID: <001a01c9fc1c$c6102340$e79a5545@amd> Brian, you've got the formulas right! You will be making a home built version of the "department store" telescope but you will at the least, say that you built it. The larger diameter eye lens iwll help a bit as it will give a bigger field of view. There is a ray that goes through a lens that is called the "Chief Ray" and it is the ray which goes through the lens without changing direction and it goes through a point of the lens called the "Principle Point". This ray has some special properties as it doesn't matter what angle it comes into the lens, it goes out of the lens at the same angle. It may be offset by the glass in the lens (especially true with complex camera lenses!) but the angle remains the same. This ray is useful as it defines the field of view characteristics of the lens. As such, if you know that your eye lens is 22mm in opening, you will know that simple geometry will show how much of a field of view you will have with that 550mm focal length of the field lens. It will also show you that a larger eye lens will tend (there are limits here!) produce a larger field of view. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From ericandroberta at sbcglobal.net Sat Jul 4 06:24:45 2009 From: ericandroberta at sbcglobal.net (D ERIC ALLEN) Date: Fri, 3 Jul 2009 14:24:45 -0700 (PDT) Subject: [ATM] ATM: Speculum metal Message-ID: <334743.35130.qm@web80505.mail.mud.yahoo.com> Speculum metal is essentially brass and is ridiculously heavy.? Use steel.? It's cheaper and lighter.? Don't know how it would polish, though. Eric From arjan.te.marvelde at hetnet.nl Sat Jul 4 07:24:35 2009 From: arjan.te.marvelde at hetnet.nl (Arjan te Marvelde (hetnet)) Date: Sat, 04 Jul 2009 00:24:35 +0200 Subject: [ATM] large aluminum mirrors In-Reply-To: References: Message-ID: <4A4E8523.3090006@hetnet.nl> Labyrinth > "Sometimes the way forward is the way back" From what movie, starring a > beauty who appeared in "A Beautiful Mind", but much, much earlier. Name the > movie, win magic card trick. From stainless_steel at suddenlink.net Sat Jul 4 10:08:48 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Fri, 3 Jul 2009 20:08:48 -0500 Subject: [ATM] Fw: ATM: Speculum metal Message-ID: ----- Original Message ----- From: To: "D ERIC ALLEN" Sent: Friday, July 03, 2009 8:07 PM Subject: Re: [ATM] ATM: Speculum metal > Weight is simply not an issue for a competent design engineer. > > D-LZ130 > > > ----- Original Message ----- > From: "D ERIC ALLEN" > To: > Sent: Friday, July 03, 2009 4:24 PM > Subject: [ATM] ATM: Speculum metal > > > Speculum metal is essentially brass and is ridiculously heavy. Use steel. > It's cheaper and lighter. Don't know how it would polish, though. > Eric > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.375 / Virus Database: 270.13.3/2217 - Release Date: 07/03/09 > 18:11:00 > From stainless_steel at suddenlink.net Sat Jul 4 10:10:32 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Fri, 3 Jul 2009 20:10:32 -0500 Subject: [ATM] large aluminum mirrors In-Reply-To: <4A4E8523.3090006@hetnet.nl> References: <4A4E8523.3090006@hetnet.nl> Message-ID: <2685B61A08AE41C28C2CE0557BA158F8@R101> WINNER. gIVE ME TIME TO SEND YOU THE DISC WITH THE MOVIE ON IT. D-LZ129 ----- Original Message ----- From: "Arjan te Marvelde (hetnet)" To: Sent: Friday, July 03, 2009 5:24 PM Subject: Re: [ATM] large aluminum mirrors > Labyrinth >> "Sometimes the way forward is the way back" From what movie, starring a >> beauty who appeared in "A Beautiful Mind", but much, much earlier. Name >> the >> movie, win magic card trick. > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.3/2217 - Release Date: 07/03/09 18:11:00 From tstokes at pacbell.net Sat Jul 4 10:36:25 2009 From: tstokes at pacbell.net (Tom Stokes) Date: Fri, 3 Jul 2009 18:36:25 -0700 Subject: [ATM] Printing Ronchi screens Message-ID: I've written a tiny Windows program for drawing Ronchi screens. You can run it without downloading it (but with appropriate warnings from you browser). I would be interested in your findings re quality. It will be a few months before I can test it. http://www.mirrorgrindingmachine.com/PrintaRonchi/ Tom Stokes From rflrs at verizon.net Sat Jul 4 15:03:22 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Sat, 04 Jul 2009 02:03:22 -0400 Subject: [ATM] Dual Triplet In-Reply-To: <4A381C1E.6090202@verizon.net> References: <3183d250711090321l23b17e67y71bc7189909483f8@mail.gmail.com> <920703.73390.qm@web82005.mail.mud.yahoo.com> <4A19EB73.40300@verizon.net> <4A2CDDAF.6010308@verizon.net> <4A381C1E.6090202@verizon.net> Message-ID: <4A4EF0AA.2040308@verizon.net> Richard F.L.R. Snashall wrote: >> However, by putting a Barium flint first, the >> spherochromatism can be reduced, at the expense >> of some lateral color (again, 135 mm f/12): >> >> http://mysite.verizon.net/rflrs/trp02-30x.atm ATMOS input file >> http://mysite.verizon.net/rflrs/trp02-30x.len OSLO input file >> http://mysite.verizon.net/rflrs/trp02-30x.txt TEXT prescription >> http://mysite.verizon.net/rflrs/trp02-30x.zmx ZEMAX input file >> Or, accepting a bit of field curvature, this Petzval-like oiled triplet pair has quite good visual performance (155 mm f/6): http://mysite.verizon.net/rflrs/Ptz12-39x.atm ATMOS input file http://mysite.verizon.net/rflrs/Ptz12-39x.len OSLO input file http://mysite.verizon.net/rflrs/Ptz12-39x.txt TEXT prescription http://mysite.verizon.net/rflrs/Ptz12-39x.zmx ZEMAX input file The Visual Strehl here is about 0.96 at the edge of the 2.6 degree (42.4 mm) field -- in spite of the requirement that the short flint central element of each triplet be isoconcave. As I mentioned, the field is curved, but not strongly, with a RoC 10% larger than the focal length. From gfbrandenburg at yahoo.com Sat Jul 4 21:44:58 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Sat, 4 Jul 2009 05:44:58 -0700 (PDT) Subject: [ATM] refractor clarification Message-ID: <711390.95195.qm@web111513.mail.gq1.yahoo.com> You can make a refractor like this, but there are other ways as well, that will be more color-corrected. Use Surplus Shed's lens index utility and find a achromatic doublet that you can use as the front element, and then use one of their inexpensive eyepiedes as the eyepiece. The rest of your calculations appear OK. I did something similar and used various plastic plumbing parts to fit them all together. Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Fri, 7/3/09, Brian Karlsen wrote: > From: Brian Karlsen > Subject: [ATM] refractor clarification > To: atm at atmlist.net > Date: Friday, July 3, 2009, 5:25 AM > Hi all I just joined the list and am > looking forward to learning much more > about this interesting hobby. > > I am in the process of designing and sourcing the > components for my first > non department store "aka toy"? and would like to > check my thinking before I > start purchasing. > > the plan is for a simple refractor? 2 convex > lenses? mounted in a piece of > PVC pipe the lenses I am looking at are from http://www.surplusshed.com/ > > For? the primary lens I am looking at the L10238 lens > 83mm diameter 550mm fl > > for the eyepiece lens I plan on using the? L3993 22mm > diameter 18mm fl > > from what I understand these should be spaced > proximately? ? fl 1+fl 2= > 550+18=568mm apart and will give a magnification > of???fl 1 / fl 2= 550/18= > 30.5x > > are all these calculations correct, am I mising > anything,? would this work, > I am also going to make it so the distance betweel the lens > is adjustable an > inch or 2 for focus any sugestions. > > thanks in anticipation of youre responces. > > Brian > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From atmer at flash.net Sun Jul 5 00:49:28 2009 From: atmer at flash.net (Anthony Stillman) Date: Sat, 4 Jul 2009 08:49:28 -0700 (PDT) Subject: [ATM] ATM: Speculum metal Message-ID: <499941.5078.qm@web82004.mail.mud.yahoo.com> Speculum is bronze. A alloy of tin and copper. Brass is an alloy of zinc and copper. Ideal speculum is by weight one third tin and two thirds copper. This ratio corresponds almost exactly to that of Cu41Sn11, the delta phase of the alloy. Speculum is however not a single phase alloy but rather a combination of the intermetalic delta, epsilon and eta phases along with some alpha solid solution. How much of each and the distribution within a casting is dependent on the thermal history. A good deal of what has been written about speculum since it fell out of favor is erroneous. For example, it does not tarnishes quickly. The mirrors I made four years ago, while not as bright as they once were, are still very shiny. The best reasons not to use this metal for telescope mirrors are rarely emphasized in what little literature there is. They are, how difficult it is to grind and polish, and it's proclivity for tiny voids (porosity as a result of the inverse steam reaction) in castings. Bronze is heavy, speculum 8.9 grams per centimeter cubed, pyrex is 2.23. And then there's the name. Roughly two centuries ago an incredibly imaginative doctor stole the Latin word for mirror and metal to use as the name for a tool which for the previous three millenium was called a katopter. Now it's nearly impossible to mention the alloy without inspiring winces and giggles. I've taken to calling it high tin bronze and mirror metal. Anthony From richard1941 at gmail.com Sun Jul 5 07:23:01 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Sat, 4 Jul 2009 17:23:01 -0500 Subject: [ATM] ATM: Speculum metal In-Reply-To: <499941.5078.qm@web82004.mail.mud.yahoo.com> References: <499941.5078.qm@web82004.mail.mud.yahoo.com> Message-ID: <3e5fde0d0907041523l60dd11cxc53a20bcbae93f72@mail.gmail.com> This tool, what exactly does the ATM do with it? Was the doctor who named the tool a telescope maker? Back in the 19th century, "doctors" did lots of strange and interesting things like naturopathy, homeopathy, chiropractic, and all that stuff whose physical principals are beyond me. From foreilly at bestweb.net Mon Jul 6 04:48:59 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Sun, 5 Jul 2009 15:48:59 -0400 Subject: [ATM] Low Pressure Sodium Ballast Message-ID: I am making three two sided flats. Polishing is almost complete. I will be figuring shortly. I need to find a source of monochromatic light. To that end I have purchased a 35 watt LPS/SOX bulb for use in a simple inteferometer. I need to find a 120VAC 35 watt ballast. Does anyone know who sells these ballasts? Francis J. O'Reilly From vorblesnak at peak.org Mon Jul 6 03:16:08 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Sun, 5 Jul 2009 11:16:08 -0700 (PDT) Subject: [ATM] Printing Ronchi screens Message-ID: <4128.69.59.200.230.1246817768.squirrel@webmail.peak.org> I pulled it in and tried it on two printers, an old HP Laserjet 6P and a Lexmark 2420 Optra S. It printed instantly on both printers. The image was the same size on both prints. The lexmark did a better job, it has better resolution. I printed both the 100 lpi and a 50 lpi. Slick little program Tom, thank you! David Davis Toledo, OR 97391 Tom wrote: I've written a tiny Windows program for drawing Ronchi screens. You can run it without downloading it (but with appropriate warnings from you browser). I would be interested in your findings re quality. It will be a few months before I can test it. http://www.mirrorgrindingmachine.com/PrintaRonchi/ Tom Stokes From rmay at nethere.com Mon Jul 6 07:25:15 2009 From: rmay at nethere.com (Bob May) Date: Sun, 5 Jul 2009 15:25:15 -0700 Subject: [ATM] Low Pressure Sodium Ballast References: Message-ID: <000401c9fdbf$79032580$a9ff1345@amd> Francis, you're going the expensive way. Much cheaper is to use a compact flourscent bulb and filter for the green. The cheap green vinyl filter material you can get at a plastics store will do fine as would any other deep green filter material. There are two kinds of the compact bulbs, one has a low level of broadband emissions while the other (more desired) has only the bright lines. Use an opal glass cover (ceiling fixture globe of substantial size and put the green filter inside and put the whole light into a box with an open front and a big hole in the top for the light and you've got a nice green light source and viewing chamber for it. Use in a darkened room and the fringes will pop up very nicely. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From stainless_steel at suddenlink.net Mon Jul 6 07:22:24 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Sun, 5 Jul 2009 17:22:24 -0500 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: References: Message-ID: Francis, all: Ballast is something (water) that used to be carried in tons and tons and tons of weight in the big rigid airships (never in a so-called blimp; they are a so-called "pressure ship", which, when it ascends above helium envelope volume height, the internal ballonet contracts to let the helium expand. Can't do that with a ship with rigid framework. When a blimp descends to where it was "weighed off" (adjusting for ambient pressure changes) the helium contracts under the increasing air pressure in the ballonet. The internal ballonet is constantly kept slightly above ambient pressure by being fed with the two big fans (propellers) to enable the blimp to keep its shape, keep the envelope stiff. There is no hull framework in a blimp. Hence, the tec hnically correct term for a blimp now is "pressure ship". Over a dozen good wsized ones are flying, world wide. Zeppelin is stilll in business and has turned out her first largoish semi-rigid touring airship (with our helium in her). Now, to stay approximately on topic, someone explain why flourescent lamps have a thingie called a 'ballast tube". The luxury airship R-101, when she slipped the high mast on her maiden voyage to India, had to drop, IMMEDIATELY she came loose from the mast, HALF her ballast, she sank so fast. Leaking gas badly in the forward parrt of the hull. This was not the fault of the engineers who modified her; it was the fault of Christopher Birdwood Thompson and the Air Ministry, who insisted on the modifications (risky ones) instead of letting Richmond have lighter engines, as the engineers of the Vickers 100 did (changed engine specifications 3 times). Very successfull. Air Ministry had her broken up to save face after R-101 crashed with heavy casualties. Thompson died a few hours later in the wreck of the R-101. No structural failure with stainless steel framework; loss of gas from the leaks, and badly ripped off forward envelope at 63 mph. Envelope was made of wrong stuff with the dope (dope: what radio controlled, and many full sized aircraft with fabric covered wings are coated with) http://www.aht.ndirect.co.uk/ First two big ships to have cabins and other rooms inside the hull. Germans stood around, at the air ministry's invitation, in 1929 watching them build R-101. They took the idea to heart and incorporated them into the world's two most advanced and largest aiorships: D-LZ129 (Hindenburg) and D-LZ130. Only injury to the Hindenburg was caused by the lack of helium. Goering had D-LZ130 broken up for her aluminum, which he "needed" to build more Bf-109s. He only had 34,000 of these excellent (but mnot good enough) hogs built before the war was over. All he needed befoere war's end was 3,000 Me-262s, instead of 34,000 Bf-109s and other assorted birds. So are the ballast tubes in flourescent lighting used to make the tubes "LIGHTER" Lighter than air, as were the big ships? Is that what that term means, in this context? Enlighten me, someone. D-LZ130 ----- Original Message ----- From: "Francis J. O'Reilly" To: Sent: Sunday, July 05, 2009 2:48 PM Subject: [ATM] Low Pressure Sodium Ballast >I am making three two sided flats. Polishing is almost complete. I will be >figuring shortly. I need to find a source of monochromatic light. To that >end I have purchased a 35 watt LPS/SOX bulb for use in a simple >inteferometer. I need to find a 120VAC 35 watt ballast. Does anyone know >who sells these ballasts? > > Francis J. O'Reilly > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2219 - Release Date: 07/05/09 05:53:00 From burrjaw at earthlink.net Mon Jul 6 08:39:02 2009 From: burrjaw at earthlink.net (Jim Burrows) Date: Sun, 05 Jul 2009 16:39:02 -0700 Subject: [ATM] Stroke and starlap solution. Message-ID: Like almost every ATM, having problems with figuring strokes not doing the job? When I asked Bob Goff this question he said, "Jim, get a spindle." Since there's not much stroke choice on a turntable, you're forced to use deformed laps ("starlaps"). My starlap program for spindle spells just designs the starlap petals to match the mirror deviations, i.e., more pitch at high zones. For stroke laps, it assumes a 2/5 stroke, perfect contact, and uniform pressure. This mostly works, but there's still plenty of variations - different strokes, lap slumping, imperfect contact, changing figure goal, etc. So I've gone one step further in starlap design - a program that uses what the last spell did to design a better starlap. You input 3 deviation files to the program: the deviations used to design the spell's starlap, and the deviations before and after the spell. The program then outputs the starlap design that should get rid of the remaining deviations using the same stroke. Download: http://home.earthlink.net/~burrjaw/public/id_star.zip (Win32, 2009-07-05, 0.94 MB) That "id" is Intelligent Design . -- Jim Burrows -- http://home.earthlink.net/~burrjaw -- mailto:burrjaw at earthlink.net -- Seattle N47.4723 W122.3662 (WGS84) From foreilly at verizon.net Mon Jul 6 08:42:50 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Sun, 05 Jul 2009 19:42:50 -0400 Subject: [ATM] Low Pressure Sodium Ballast References: Message-ID: <6E544903B3A6454B9F1277CB01511FA7@HELENYLCMWAV95> David, I don't want to start a flame war, it's not my style. Further, I like and respect you, but all I want is a straight answer to a straight question. I am interested in making an interferometer to test my optical flats. I like Low Pressure Sodium light because I know the wavelength of the light, 589.0 and 589.6 nanometers. That puts some meaning into any wave rating that I may someday attribute to my flat and the subsequent optics that I test. That being said, at this time in my optics career, I am not really interested in applying arbitrary number ratings to my optics, however it might be a nice option in the future. A ballast is needed to limit the current flowing through the bulb, a capacitor and ignitor are needed to start the bulb. Francis J. O'Reilly ----- Original Message ----- From: To: "ATM list" ; "Francis J. O'Reilly" Sent: Sunday, July 05, 2009 6:22 PM Subject: Re: [ATM] Low Pressure Sodium Ballast > Francis, all: > > Ballast is something (water) that used to be carried in tons and tons and > tons of weight in the big rigid airships (never in a so-called blimp; they > are a so-called "pressure ship", which, when it ascends above helium > envelope volume height, the internal ballonet contracts to let the helium > expand. Can't do that with a ship with rigid framework. When a blimp > descends to where it was "weighed off" (adjusting for ambient pressure > changes) the helium contracts under the increasing air pressure in the > ballonet. The internal ballonet is constantly kept slightly above ambient > pressure by being fed with the two big fans (propellers) to enable the > blimp to keep its shape, keep the envelope stiff. > There is no hull framework in a blimp. Hence, the tec hnically correct > term for a blimp now is "pressure ship". Over a dozen good wsized ones are > flying, world wide. Zeppelin is stilll in business and has turned out her > first largoish semi-rigid touring airship (with our helium in her). > > Now, to stay approximately on topic, someone explain why flourescent lamps > have a thingie called a 'ballast tube". > > The luxury airship R-101, when she slipped the high mast on her maiden > voyage to India, had to drop, IMMEDIATELY she came loose from the mast, > HALF her ballast, she sank so fast. Leaking gas badly in the forward parrt > of the hull. This was not the fault of the engineers who modified her; it > was the fault of Christopher Birdwood Thompson and the Air Ministry, who > insisted on the modifications (risky ones) instead of letting Richmond > have lighter engines, as the engineers of the Vickers 100 did (changed > engine specifications 3 times). Very successfull. Air Ministry had her > broken up to save face after R-101 crashed with heavy casualties. > > Thompson died a few hours later in the wreck of the R-101. No structural > failure with stainless steel framework; loss of gas from the leaks, and > badly ripped off forward envelope at 63 mph. Envelope was made of wrong > stuff with the dope (dope: what radio controlled, and many full sized > aircraft with fabric covered wings are coated with) > > http://www.aht.ndirect.co.uk/ > > First two big ships to have cabins and other rooms inside the hull. > Germans stood around, at the air ministry's invitation, in 1929 watching > them build R-101. They took the idea to heart and incorporated them into > the world's two most advanced and largest aiorships: D-LZ129 (Hindenburg) > and D-LZ130. Only injury to the Hindenburg was caused by the lack of > helium. Goering had D-LZ130 broken up for her aluminum, which he "needed" > to build more Bf-109s. He only had 34,000 of these excellent (but mnot > good enough) hogs built before the war was over. All he needed befoere > war's end was 3,000 Me-262s, instead of 34,000 Bf-109s and other assorted > birds. > > So are the ballast tubes in flourescent lighting used to make the tubes > "LIGHTER" Lighter than air, as were the big ships? Is that what that term > means, in this context? Enlighten me, someone. > > D-LZ130 > > ----- Original Message ----- > From: "Francis J. O'Reilly" > To: > Sent: Sunday, July 05, 2009 2:48 PM > Subject: [ATM] Low Pressure Sodium Ballast > > >>I am making three two sided flats. Polishing is almost complete. I will be >>figuring shortly. I need to find a source of monochromatic light. To that >>end I have purchased a 35 watt LPS/SOX bulb for use in a simple >>inteferometer. I need to find a 120VAC 35 watt ballast. Does anyone know >>who sells these ballasts? >> >> Francis J. O'Reilly >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.375 / Virus Database: 270.13.5/2219 - Release Date: 07/05/09 > 05:53:00 > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mbartels at bbastrodesigns.com Mon Jul 6 09:07:43 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sun, 5 Jul 2009 17:07:43 -0700 Subject: [ATM] Stroke and starlap solution. In-Reply-To: References: Message-ID: <00cc01c9fdcd$cd810ec0$68832c40$@com> Temperature is the biggest culprit in changing figuring results. What I do in the winter is far different than what I do in the summer, and I have an insulated shop that changes temperatures across the seasons maybe 20F! Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Jim Burrows Sent: Sunday, July 05, 2009 4:39 PM To: ATM list Subject: [ATM] Stroke and starlap solution. Like almost every ATM, having problems with figuring strokes not doing the job? When I asked Bob Goff this question he said, "Jim, get a spindle." Since there's not much stroke choice on a turntable, you're forced to use deformed laps ("starlaps"). My starlap program for spindle spells just designs the starlap petals to match the mirror deviations, i.e., more pitch at high zones. For stroke laps, it assumes a 2/5 stroke, perfect contact, and uniform pressure. This mostly works, but there's still plenty of variations - different strokes, lap slumping, imperfect contact, changing figure goal, etc. So I've gone one step further in starlap design - a program that uses what the last spell did to design a better starlap. You input 3 deviation files to the program: the deviations used to design the spell's starlap, and the deviations before and after the spell. The program then outputs the starlap design that should get rid of the remaining deviations using the same stroke. Download: http://home.earthlink.net/~burrjaw/public/id_star.zip (Win32, 2009-07-05, 0.94 MB) That "id" is Intelligent Design . -- Jim Burrows -- http://home.earthlink.net/~burrjaw -- mailto:burrjaw at earthlink.net -- Seattle N47.4723 W122.3662 (WGS84) _______________________________________________ ATM mailing list http://www.atmlist.net/ From foreilly at verizon.net Mon Jul 6 09:17:59 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Sun, 05 Jul 2009 20:17:59 -0400 Subject: [ATM] Low Pressure Sodium Ballast References: <000401c9fdbf$79032580$a9ff1345@amd> Message-ID: <37AC69B3517F4AF4A3EA93CF28A7C553@HELENYLCMWAV95> Bob, Thank you for your thoughts. I acknbowledge that yours certainly is one way to successfully get "fringes". Best, Francis J. O'Reilly From rflrs at verizon.net Mon Jul 6 11:19:43 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Sun, 05 Jul 2009 22:19:43 -0400 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: References: Message-ID: <4A515F3F.106@verizon.net> Francis J. O'Reilly wrote: > I am making three two sided flats. Polishing is almost complete. I will be figuring shortly. I need to find a source of monochromatic light. To that end I have purchased a 35 watt LPS/SOX bulb for use in a simple inteferometer. I need to find a 120VAC 35 watt ballast. Does anyone know who sells these ballasts? I might have, via Google search, found one, albeit here in Hudson (I tried to restrict myself to E. Coast, anyway): https://www.altestore.com/store/ Might be a bit of a travel from where you are, though. Maybe you can find one more local than that, even. From gfbrandenburg at yahoo.com Mon Jul 6 11:44:36 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Sun, 5 Jul 2009 19:44:36 -0700 (PDT) Subject: [ATM] Low Pressure Sodium Ballast Message-ID: <511004.23551.qm@web111503.mail.gq1.yahoo.com> Francis, I gave up on LPS or HPS sodium lights when I needed fringes for my Lurie-Houghton project (which has so far not been successful) precisely because the prices I found for the ballasts, etc, were several hundred dollars. The bulbs themselves are under $30, but the ballasts and fixtures were way beyond what I was willing to pay. However, if you have a surplus place near you that sells recycled building materials (like our own Community Forklift in nearby Hyattsville, MD), then you may get lucky. I didn't. So I went via a much cheaper route, which you may (or may not) recall seeing when you visited our DC workshop. I went to a theatrical supply store armed with a cheap ($15) spectroscope, and looked at their sample swatches to see which ones would filter out everything except for one line of some color from a fluorescent light. I don't exactly recall which two sheets of which colors I used, but they were both green to the eye. They both let through the 546.1 nm green mercury vapor line, and one of them cut off everything with a shorter wavelength, and the other one cut off everything with a longer wavelength. Total cost for the two gels, which are about the size of a normal 8 by 11.5" piece of paper: roughly ten dollars. Then I dismantled and reassembled a couple of short-tube fluorescent light fixtures that I was going to throw away anyway, and built them into a box. The spectroscope is quite helpful. You can not only see the spectral transmission curve printed out on the little piece of paper next to the actual plastic gel, but you can also check with your own eye to see if it's correct. Plus you can take two of the little sample gels out and put them together and see what happens. I also found that different fluorescent lights evidently have different color-emitting substances coating the inside of their tubes, which causes some weird effects. In particular, I found that a lot of the compact fluorescent lights have TWO green lines, right next to each other. I don't know which one is the 546.1 nm line. Perhaps someone on this list can enlighten us. You can also look here: http://www.gamonline.com/catalog/gamcolor/index.php For better resolution, I eventually changed to "black light" fluorescent bulbs because more of the green was emitted, and less of other colors. I was pretty sure I took some photos of my setup, but I can't find any after a 20-minute search on this computer. So here are a few URLs: http://www.indiamart.com/prismsindia/pcat-gifs/products-small/monochromaticlightsource.jpg aka http://tinyurl.com/monolitebox for short, or else https://rdl.train.army.mil/soldierPortal/atia/adlsc/view/public/8858-1/accp/mm0478/mm047880030.gif or http://tinyurl.com/millitebox for short The slanted part is an ordinary piece of glass that is frosted on the inside and smooth on the outside. You attach the two gels on the inside of this glass. Plus, put some white (or green) crepe paper inside that as a diffuser. Inside the top of the box, that's where you install your shorty fluorescent lights. Works great! Total cost was minimal, under $25, and almost all of that was for the gels and the black lights. Good luck on your flats project, Francis. And, BTW, if you want relatively inexpensive refrence flats, Surplus Shed has them. Guy From hermit at outofoptions.org Mon Jul 6 11:51:51 2009 From: hermit at outofoptions.org (hermit) Date: Sun, 05 Jul 2009 22:51:51 -0400 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: <511004.23551.qm@web111503.mail.gq1.yahoo.com> References: <511004.23551.qm@web111503.mail.gq1.yahoo.com> Message-ID: <4A5166C7.5050504@outofoptions.org> I was looking at theatrical gels for photography a while back. At least one site had the wave length characteristics listed. I don't remember. Lee and Roscoe make them. Ken Lowther Guy Brandenburg wrote: > Francis, > > I gave up on LPS or HPS sodium lights when I needed fringes for my Lurie-Houghton project (which has so far not been successful) precisely because the prices I found for the ballasts, etc, were several hundred dollars. The bulbs themselves are under $30, but the ballasts and fixtures were way beyond what I was willing to pay. However, if you have a surplus place near you that sells recycled building materials (like our own Community Forklift in nearby Hyattsville, MD), then you may get lucky. I didn't. > > So I went via a much cheaper route, which you may (or may not) recall seeing when you visited our DC workshop. I went to a theatrical supply store armed with a cheap ($15) spectroscope, and looked at their sample swatches to see which ones would filter out everything except for one line of some color from a fluorescent light. > > I don't exactly recall which two sheets of which colors I used, but they were both green to the eye. They both let through the 546.1 nm green mercury vapor line, and one of them cut off everything with a shorter wavelength, and the other one cut off everything with a longer wavelength. Total cost for the two gels, which are about the size of a normal 8 by 11.5" piece of paper: roughly ten dollars. > > Then I dismantled and reassembled a couple of short-tube fluorescent light fixtures that I was going to throw away anyway, and built them into a box. The spectroscope is quite helpful. You can not only see the spectral transmission curve printed out on the little piece of paper next to the actual plastic gel, but you can also check with your own eye to see if it's correct. Plus you can take two of the little sample gels out and put them together and see what happens. I also found that different fluorescent lights evidently have different color-emitting substances coating the inside of their tubes, which causes some weird effects. In particular, I found that a lot of the compact fluorescent lights have TWO green lines, right next to each other. I don't know which one is the 546.1 nm line. Perhaps someone on this list can enlighten us. > You can also look here: > > http://www.gamonline.com/catalog/gamcolor/index.php > > For better resolution, I eventually changed to "black light" fluorescent bulbs because more of the green was emitted, and less of other colors. > I was pretty sure I took some photos of my setup, but I can't find any after a 20-minute search on this computer. So here are a few URLs: > > http://www.indiamart.com/prismsindia/pcat-gifs/products-small/monochromaticlightsource.jpg > > aka > > http://tinyurl.com/monolitebox > > for short, or else > > https://rdl.train.army.mil/soldierPortal/atia/adlsc/view/public/8858-1/accp/mm0478/mm047880030.gif > > or > > http://tinyurl.com/millitebox > for short > > The slanted part is an ordinary piece of glass that is frosted on the inside and smooth on the outside. You attach the two gels on the inside of this glass. Plus, put some white (or green) crepe paper inside that as a diffuser. Inside the top of the box, that's where you install your shorty fluorescent lights. > > Works great! Total cost was minimal, under $25, and almost all of that was for the gels and the black lights. > > Good luck on your flats project, Francis. And, BTW, if you want relatively inexpensive refrence flats, Surplus Shed has them. > > Guy > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From gfbrandenburg at yahoo.com Mon Jul 6 11:55:02 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Sun, 5 Jul 2009 19:55:02 -0700 (PDT) Subject: [ATM] Low Pressure Sodium Ballast Message-ID: <491670.9886.qm@web111501.mail.gq1.yahoo.com> The first URL I gave has such a thing, also. Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Sun, 7/5/09, hermit wrote: > From: hermit > Subject: Re: [ATM] Low Pressure Sodium Ballast > To: > Cc: "ATM list" > Date: Sunday, July 5, 2009, 10:51 PM > I was looking at theatrical gels for > photography a while back.? At least > one site had the wave length characteristics listed.? > I don't remember.? > Lee and Roscoe make them. > > Ken Lowther > > Guy Brandenburg wrote: > > Francis, > > > > I gave up on LPS or HPS sodium lights when I needed > fringes for my Lurie-Houghton project (which has so far not > been successful) precisely because the prices I found for > the ballasts, etc, were several hundred dollars. The bulbs > themselves are under $30, but the ballasts and fixtures were > way beyond what I was willing to pay. However, if you have a > surplus place near you that sells recycled building > materials (like our own Community Forklift in nearby > Hyattsville, MD), then you may get lucky. I didn't. > > > > So I went via a much cheaper route, which you may (or > may not) recall seeing when you visited our DC workshop. I > went to a theatrical supply store armed with a cheap ($15) > spectroscope, and looked at their sample swatches to see > which ones would filter out everything except for one line > of some color from a fluorescent light. > > > > I don't exactly recall which two sheets of which > colors I used, but they were both green to the eye. They > both let through the 546.1 nm green mercury vapor line, and > one of them cut off everything with a shorter wavelength, > and the other one cut off everything with a longer > wavelength. Total cost for the two gels, which are about the > size of a normal 8 by 11.5" piece of paper: roughly ten > dollars. > > > > Then I dismantled and reassembled a couple of > short-tube fluorescent light fixtures that I was going to > throw away anyway, and built them into a box. The > spectroscope is quite helpful. You can not only see the > spectral transmission curve printed out on the little piece > of paper next to the actual plastic gel, but you can also > check with your own eye to see if it's correct. Plus you can > take two of the little sample gels out and put them together > and see what happens. I also found that different > fluorescent lights evidently have different color-emitting > substances coating the inside of their tubes, which causes > some weird effects. In particular, I found that a lot of the > compact fluorescent lights have TWO green lines, right next > to each other. I don't know which one is the 546.1 nm line. > Perhaps someone on this list can enlighten us. > > You can also look here: > > > > http://www.gamonline.com/catalog/gamcolor/index.php > > > > For better resolution, I eventually changed to "black > light" fluorescent bulbs because more of the green was > emitted, and less of other colors. > > I was pretty sure I took some photos of my setup, but > I can't find any after a 20-minute search on this computer. > So here are a few URLs: > > > > http://www.indiamart.com/prismsindia/pcat-gifs/products-small/monochromaticlightsource.jpg > > > > aka > > > > http://tinyurl.com/monolitebox > > > > for short, or else > > > > https://rdl.train.army.mil/soldierPortal/atia/adlsc/view/public/8858-1/accp/mm0478/mm047880030.gif > > > > or > > > > http://tinyurl.com/millitebox > > for short > > > > The slanted part is an ordinary piece of glass that is > frosted on the inside and smooth on the outside. You attach > the two gels on the inside of this glass. Plus, put some > white (or green) crepe paper inside that as a diffuser. > Inside the top of the box, that's where you install your > shorty fluorescent lights. > > > > Works great! Total cost was minimal, under $25, and > almost all of that was for the gels and the black lights. > > > > Good luck on your flats project, Francis. And, BTW, if > you want relatively inexpensive refrence flats, Surplus Shed > has them. > > > > Guy > > > > > >? ? ??? > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > >??? > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From hermit at outofoptions.org Mon Jul 6 12:04:03 2009 From: hermit at outofoptions.org (hermit) Date: Sun, 05 Jul 2009 23:04:03 -0400 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: <491670.9886.qm@web111501.mail.gq1.yahoo.com> References: <491670.9886.qm@web111501.mail.gq1.yahoo.com> Message-ID: <4A5169A3.2020104@outofoptions.org> Just curious. Enough to ask but not enough to look it up. How narrow is that band from the LPS light as compared to an LED? From foreilly at verizon.net Mon Jul 6 19:01:19 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Mon, 06 Jul 2009 06:01:19 -0400 Subject: [ATM] Low Pressure Sodium Ballast References: <4A515F3F.106@verizon.net> Message-ID: <8DF1772168B3472B8D8920FD77942575@HELENYLCMWAV95> Richard, Hudson eh? I'm trying a case in Kingston for the next three days. Hudson is right across the river. I'll look into this, but they sell 12VDC ballasts, I'm still looking for 120 VAC. Thank you for your help. Francis J. O'Reilly ----- Original Message ----- From: "Richard F.L.R. Snashall" To: Sent: Sunday, July 05, 2009 10:19 PM Subject: Re: [ATM] Low Pressure Sodium Ballast > Francis J. O'Reilly wrote: >> I am making three two sided flats. Polishing is almost complete. I will >> be figuring shortly. I need to find a source of monochromatic light. To >> that end I have purchased a 35 watt LPS/SOX bulb for use in a simple >> inteferometer. I need to find a 120VAC 35 watt ballast. Does anyone know >> who sells these ballasts? > I might have, via Google search, found one, albeit here in Hudson > (I tried to restrict myself to E. Coast, anyway): > > https://www.altestore.com/store/ > > Might be a bit of a travel from where you are, though. Maybe you > can find one more local than that, even. > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From foreilly at verizon.net Mon Jul 6 19:02:22 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Mon, 06 Jul 2009 06:02:22 -0400 Subject: [ATM] Low Pressure Sodium Ballast References: <491670.9886.qm@web111501.mail.gq1.yahoo.com> <4A5169A3.2020104@outofoptions.org> Message-ID: <7D1B3E8E274A4ED384F336A2FCE0F9E6@HELENYLCMWAV95> Pretty narrow from my understanding. Thank you for your reply. Francis J. O'Reilly ----- Original Message ----- From: "hermit" Cc: "ATM list" Sent: Sunday, July 05, 2009 11:04 PM Subject: Re: [ATM] Low Pressure Sodium Ballast > Just curious. Enough to ask but not enough to look it up. How narrow > is that band from the LPS light as compared to an LED? > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From richard at foucault.co.uk Mon Jul 6 19:23:47 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Mon, 6 Jul 2009 11:23:47 +0100 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: References: Message-ID: <1922173196.20090706112347@foucault.co.uk> Hello stainless, Sunday, July 5, 2009, 11:22:24 PM, you wrote > Ballast is something (water) that used to be carried in tons and tons and > tons of weight in the big rigid airships I love the old airships, but if I want to read about them I will join an airship list. Can you please stop these off topic ramblings? -- Best regards, Richard in the UK From lowe at nanotechsys.com Mon Jul 6 19:53:51 2009 From: lowe at nanotechsys.com (Jeff Lowe) Date: Mon, 06 Jul 2009 06:53:51 -0400 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: References: Message-ID: <4A51D7BF.3000504@nanotechsys.com> ----- Original Message ----- From: "Francis J. O'Reilly" To: Sent: Sunday, July 05, 2009 2:48 PM Subject: [ATM] Low Pressure Sodium Ballast >I am making three two sided flats. Polishing is almost complete. I will be >figuring shortly. I need to find a source of monochromatic light. To that >end I have purchased a 35 watt LPS/SOX bulb for use in a simple >inteferometer. I need to find a 120VAC 35 watt ballast. Does anyone know >who sells these ballasts? > > Francis J. O'Reilly > _______________________________________________ > ATM mailing list http://www.atmlist.net/ Hi Francis, If you make it back up to Vermont before the Stellafane convention, we have several light boxes and could loan you one. -- Jeff Lowe From daze39 at earthlink.net Mon Jul 6 21:45:16 2009 From: daze39 at earthlink.net (David Weinshenker) Date: Mon, 06 Jul 2009 05:45:16 -0700 Subject: [ATM] large aluminum mirrors In-Reply-To: <2BDFE76399EB422C88BA0E8387F52DF6@R101> References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd><4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <1687222259.20090702111309@foucault.co.uk> <2BDFE76399EB422C88BA0E8387F52DF6@R101> Message-ID: <4A51F1DC.5020101@earthlink.net> stainless_steel at suddenlink.net wrote: > Berylium is dangerous. It used to be used in flourescent (early) light rods, > but was abandoned when found to be deadly. It is used for little else now. > > Why not try "speculum metal"?- as was the universal mirror material until > Foucault tried glass, with silver on front. Speculum metal worked for the > Herschels and Lord Rosse, and many others; they had litttle to complain > about its performance. Today, we would coat the functional side with > something to raise the reflectivity. The big problem with speculum metal was that it would tarnish fairly rapidly, and the reflectivity then had to be renewed by re-polishing the surface: unless this was done with the same attention to optical accuracy as was involved in the initial polishing and figuring, the original performance of the mirror would not be maintained. It is perhaps of interest here that the castle where William Parsons, third Earl of Rosse built his 72" telescope with its speculum metal mirrors (two usable mirrors were eventually fabricated, out of five attempted castings) is still in the Parsons family, and the present owner (the seventh Earl, which I guess would make him William's great-great-grandson) has recently (within the past 10-20 years, IIRC) restored the telescope, with considerable attention to historical authenticity somewhat tempered by practicality: the positioning mechanism has been discreetly electrified, and a new aluminum mirror has been installed. I don't know what reflective coating may have been used, or if the bare polished metal surface was used as the reflector. -dave w From Harro.Treur at waternet.nl Mon Jul 6 21:55:07 2009 From: Harro.Treur at waternet.nl (Harro Treur) Date: Mon, 06 Jul 2009 14:55:07 +0200 Subject: [ATM] large aluminum mirror - at Birr Castle In-Reply-To: <4A51F1DC.5020101@earthlink.net> References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd><4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <1687222259.20090702111309@foucault.co.uk> <2BDFE76399EB422C88BA0E8387F52DF6@R101><2BDFE76399EB422C88BA0E8387F52DF6@R101> <4A51F1DC.5020101@earthlink.net> Message-ID: <4A521048.7337.00A0.0@waternet.nl> Here you can find information about the present Mirror at Birr Castle: http://zuserver2.star.ucl.ac.uk/~sk/osl/projects/birr/birr.html Beste regards Harro Treur ------------------------- >>> David Weinshenker 14:45 Maandag 6 Juli 2009 >>> stainless_steel at suddenlink.net wrote: > Berylium is dangerous. It used to be used in flourescent (early) light rods, > but was abandoned when found to be deadly. It is used for little else now. > > Why not try "speculum metal"?- as was the universal mirror material until > Foucault tried glass, with silver on front. Speculum metal worked for the > Herschels and Lord Rosse, and many others; they had litttle to complain > about its performance. Today, we would coat the functional side with > something to raise the reflectivity. The big problem with speculum metal was that it would tarnish fairly rapidly, and the reflectivity then had to be renewed by re-polishing the surface: unless this was done with the same attention to optical accuracy as was involved in the initial polishing and figuring, the original performance of the mirror would not be maintained. It is perhaps of interest here that the castle where William Parsons, third Earl of Rosse built his 72" telescope with its speculum metal mirrors (two usable mirrors were eventually fabricated, out of five attempted castings) is still in the Parsons family, and the present owner (the seventh Earl, which I guess would make him William's great-great-grandson) has recently (within the past 10-20 years, IIRC) restored the telescope, with considerable attention to historical authenticity somewhat tempered by practicality: the positioning mechanism has been discreetly electrified, and a new aluminum mirror has been installed. I don't know what reflective coating may have been used, or if the bare polished metal surface was used as the reflector. -dave w _______________________________________________ ATM mailing list http://www.atmlist.net/ ********************************************************************************************** Waternet is de gemeenschappelijke organisatie van het waterschap Amstel, Gooi en Vecht en de gemeente Amsterdam. ********************************************************************************************** De informatie verzonden in dit E-mail bericht is uitsluitend bestemd voor de geadresseerde. Gebruik van deze informatie door anderen dan de geadresseerde is verboden. Openbaarmaking, vermenigvuldiging, verspreiding en/of verstrekking van deze informatie aan derden is niet toegestaan. Waternet staat niet in voor de juiste overbrenging van de inhoud van een verzonden E-mail, noch voor tijdige ontvangst daarvan. The information contained in this communication is confidential and may be legally privileged. It is intended solely for the use of the individual or entity to whom it is addressed and others authorised to receive it.If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution or taking any action in reliance of the content of this information is strictly prohibited and may be unlawful. Waternet is neither liable for the proper and complete transmission of the information contained in this communication nor for any delay in its receipt. *********************************************************************************************** From ecairns at mcmaster.ca Mon Jul 6 23:21:03 2009 From: ecairns at mcmaster.ca (Everett Cairns) Date: Mon, 6 Jul 2009 10:21:03 -0400 Subject: [ATM] Printing Ronchi screens References: <4128.69.59.200.230.1246817768.squirrel@webmail.peak.org> Message-ID: On the topic of ronchi rulings- many trashed printers take to their grave a precision polyester? ronchi ribbon for measuring the carriage position.If you are fortunate to get two, say one at 10lines/mm and one at 9 lines/mm,they can be used as a lens focussing aid.Overlaid they display clearly visible bands about 1mm wide which will turn from black to white for every 0.1 mm relative movement between the ribbons.I tapeded one to the fixed and one to the rotating parts of my best camera lens and found it would work to return to a previous setting during focus trials. J.E. Cairns From ecairns at mcmaster.ca Mon Jul 6 23:21:22 2009 From: ecairns at mcmaster.ca (Everett Cairns) Date: Mon, 6 Jul 2009 10:21:22 -0400 Subject: [ATM] Printing Ronchi screens References: <4128.69.59.200.230.1246817768.squirrel@webmail.peak.org> Message-ID: <23958D6C2C22438EB4F63EBEB02AD000@mdg> On the topic of ronchi rulings- many trashed printers take to their grave a precision polyester? ronchi ribbon for measuring the carriage position.If you are fortunate to get two, say one at 10lines/mm and one at 9 lines/mm,they can be used as a lens focussing aid.Overlaid they display clearly visible bands about 1mm wide which will turn from black to white for every 0.1 mm relative movement between the ribbons.I tapeded one to the fixed and one to the rotating parts of my best camera lens and found it would work to return to a previous setting during focus trials. J.E. Cairns From vorblesnak at peak.org Mon Jul 6 23:45:16 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Mon, 6 Jul 2009 07:45:16 -0700 (PDT) Subject: [ATM] Printing Ronchi screens In-Reply-To: <23958D6C2C22438EB4F63EBEB02AD000@mdg> References: <4128.69.59.200.230.1246817768.squirrel@webmail.peak.org> <23958D6C2C22438EB4F63EBEB02AD000@mdg> Message-ID: <37525.159.121.96.200.1246891516.squirrel@webmail.peak.org> Clever idea. David Davis Toledo, OR 97391 > On the topic of ronchi rulings- many trashed printers take to their > grave a precision polyester? ronchi ribbon for measuring the carriage > position.If you are fortunate to get two, say one at 10lines/mm and one at > 9 > lines/mm,they can be used as a lens focussing aid.Overlaid they display > clearly visible bands about 1mm wide which will turn from black to white > for > every 0.1 mm relative movement between the ribbons.I tapeded one to the > fixed and one to the rotating parts of my best camera lens and found it > would work to return to a previous setting during focus trials. > > J.E. Cairns > > From daze39 at earthlink.net Tue Jul 7 00:37:57 2009 From: daze39 at earthlink.net (David Weinshenker) Date: Mon, 06 Jul 2009 08:37:57 -0700 Subject: [ATM] large aluminum mirrors In-Reply-To: References: <543577.83904.qm@web81902.mail.mud.yahoo.com><001601c9f695$b0b239c0$90985545@amd><4A4685AF.7050002@inreach.com> <4A469054.2060409@gmail.com><6982D539-0017-47C7-B018-17AE17A23340@psu.edu><4A4A6046.4010701@inreach.com><02941145-4953-4D74-9CD3-4C0F7D75FB24@gmail.com><4A4C1A74.3060602@inreach.com> <1687222259.20090702111309@foucault.co.uk> <2BDFE76399EB422C88BA0E8387F52DF6@R101> Message-ID: <4A521A55.9060904@earthlink.net> stainless_steel at suddenlink.net wrote: > It was used in the Gemini and Mercury heat shields, so you must be right. Actually, there was a plan to use a beryllium "heat sink" shield for Mercury but the required quantity of beryllium would have been extremely expensive... the spacecraft ended up using a phenolic-composite "ablative" shield (which absorbed the heat by gradually charring and vaporizing the surface, rather than by heating up the bulk of the metal). -dave w From invite+kd1~-1ki at facebookmail.com Tue Jul 7 01:07:23 2009 From: invite+kd1~-1ki at facebookmail.com (Christopher Ray) Date: Mon, 6 Jul 2009 09:07:23 -0700 Subject: [ATM] Check out my photos on Facebook Message-ID: Hi atm at atmlist.net, I set up a Facebook profile where I can post my pictures, videos and events and I want to add you as a friend so you can see it. First, you need to join Facebook! Once you join, you can also create your own profile. Thanks, Christopher To sign up for Facebook, follow the link below: http://www.facebook.com/p.php?i=1472303008&k=Z5GYZVU3QW5CUCEDPA25VUX&r atm at atmlist.net was invited to join Facebook by Christopher Ray. If you do not wish to receive this type of email from Facebook in the future, please click on the link below to unsubscribe. http://www.facebook.com/o.php?k=dcfa74&u=1141342719&mid=bc1e69G440781ffG0G8 Facebook's offices are located at 1601 S. California Ave., Palo Alto, CA 94304. From stainless_steel at suddenlink.net Tue Jul 7 01:49:54 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 11:49:54 -0500 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: <6E544903B3A6454B9F1277CB01511FA7@HELENYLCMWAV95> References: <6E544903B3A6454B9F1277CB01511FA7@HELENYLCMWAV95> Message-ID: <758D86AAB158493087177F7730FBF095@R101> Thank you, Francis- D-LZ130 ----- Original Message ----- From: "Francis J. O'Reilly" To: ; "ATM list" ; "Francis J. O'Reilly" Sent: Sunday, July 05, 2009 6:42 PM Subject: Re: [ATM] Low Pressure Sodium Ballast > David, > > I don't want to start a flame war, it's not my style. Further, I like and > respect you, but all I want is a straight answer to a straight question. > > I am interested in making an interferometer to test my optical flats. I > like > Low Pressure Sodium light because I know the wavelength of the light, > 589.0 > and 589.6 nanometers. That puts some meaning into any wave rating that I > may > someday attribute to my flat and the subsequent optics that I test. That > being said, at this time in my optics career, I am not really interested > in > applying arbitrary number ratings to my optics, however it might be a nice > option in the future. > > A ballast is needed to limit the current flowing through the bulb, a > capacitor and ignitor are needed to start the bulb. > > Francis J. O'Reilly > ----- Original Message ----- > From: > To: "ATM list" ; "Francis J. O'Reilly" > > Sent: Sunday, July 05, 2009 6:22 PM > Subject: Re: [ATM] Low Pressure Sodium Ballast > > >> Francis, all: >> >> Ballast is something (water) that used to be carried in tons and tons and >> tons of weight in the big rigid airships (never in a so-called blimp; >> they >> are a so-called "pressure ship", which, when it ascends above helium >> envelope volume height, the internal ballonet contracts to let the helium >> expand. Can't do that with a ship with rigid framework. When a blimp >> descends to where it was "weighed off" (adjusting for ambient pressure >> changes) the helium contracts under the increasing air pressure in the >> ballonet. The internal ballonet is constantly kept slightly above ambient >> pressure by being fed with the two big fans (propellers) to enable the >> blimp to keep its shape, keep the envelope stiff. >> There is no hull framework in a blimp. Hence, the tec hnically correct >> term for a blimp now is "pressure ship". Over a dozen good wsized ones >> are >> flying, world wide. Zeppelin is stilll in business and has turned out her >> first largoish semi-rigid touring airship (with our helium in her). >> >> Now, to stay approximately on topic, someone explain why flourescent >> lamps >> have a thingie called a 'ballast tube". >> >> The luxury airship R-101, when she slipped the high mast on her maiden >> voyage to India, had to drop, IMMEDIATELY she came loose from the mast, >> HALF her ballast, she sank so fast. Leaking gas badly in the forward >> parrt >> of the hull. This was not the fault of the engineers who modified her; it >> was the fault of Christopher Birdwood Thompson and the Air Ministry, who >> insisted on the modifications (risky ones) instead of letting Richmond >> have lighter engines, as the engineers of the Vickers 100 did (changed >> engine specifications 3 times). Very successfull. Air Ministry had her >> broken up to save face after R-101 crashed with heavy casualties. >> >> Thompson died a few hours later in the wreck of the R-101. No structural >> failure with stainless steel framework; loss of gas from the leaks, and >> badly ripped off forward envelope at 63 mph. Envelope was made of wrong >> stuff with the dope (dope: what radio controlled, and many full sized >> aircraft with fabric covered wings are coated with) >> >> http://www.aht.ndirect.co.uk/ >> >> First two big ships to have cabins and other rooms inside the hull. >> Germans stood around, at the air ministry's invitation, in 1929 watching >> them build R-101. They took the idea to heart and incorporated them into >> the world's two most advanced and largest aiorships: D-LZ129 (Hindenburg) >> and D-LZ130. Only injury to the Hindenburg was caused by the lack of >> helium. Goering had D-LZ130 broken up for her aluminum, which he "needed" >> to build more Bf-109s. He only had 34,000 of these excellent (but mnot >> good enough) hogs built before the war was over. All he needed befoere >> war's end was 3,000 Me-262s, instead of 34,000 Bf-109s and other assorted >> birds. >> >> So are the ballast tubes in flourescent lighting used to make the tubes >> "LIGHTER" Lighter than air, as were the big ships? Is that what that >> term >> means, in this context? Enlighten me, someone. >> >> D-LZ130 >> >> ----- Original Message ----- >> From: "Francis J. O'Reilly" >> To: >> Sent: Sunday, July 05, 2009 2:48 PM >> Subject: [ATM] Low Pressure Sodium Ballast >> >> >>>I am making three two sided flats. Polishing is almost complete. I will >>>be >>>figuring shortly. I need to find a source of monochromatic light. To that >>>end I have purchased a 35 watt LPS/SOX bulb for use in a simple >>>inteferometer. I need to find a 120VAC 35 watt ballast. Does anyone know >>>who sells these ballasts? >>> >>> Francis J. O'Reilly >>> _______________________________________________ >>> ATM mailing list http://www.atmlist.net/ >> >> >> -------------------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 8.5.375 / Virus Database: 270.13.5/2219 - Release Date: 07/05/09 >> 05:53:00 >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From stainless_steel at suddenlink.net Tue Jul 7 01:56:34 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 11:56:34 -0500 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: References: Message-ID: <937B044D3459411BA967E60BBAC0560E@R101> Agreed. But for a former (in another life) airship (R-101) crew member, it will always mean water to be dropped from the stainless steel marvel, R-101. D-LZ130 ----- Original Message ----- From: "Kerry Koppert" To: Sent: Sunday, July 05, 2009 8:02 PM Subject: Re: [ATM] Low Pressure Sodium Ballast > > ----- Original Message ----- > From: > To: "ATM list" ; "Francis J. O'Reilly" > > Sent: Monday, July 06, 2009 10:22 AM > Subject: Re: [ATM] Low Pressure Sodium Ballast > > >> Francis, all: >> >> Ballast is something (water) that used to be carried in tons and tons and >> tons of weight in the big rigid airships (never in a so-called blimp; >> they >> are a so-called "pressure ship", which, when it ascends above helium > > Actually that is only one meaning of the word Ballast and actually refers > to > water ballast. The word used without context (Ship ballast, railroad > ballast, electrical ballast) seems to refer to a stabilizing element, in > this case something to limit electrical current. > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From ericandroberta at sbcglobal.net Tue Jul 7 02:11:32 2009 From: ericandroberta at sbcglobal.net (ericandroberta at sbcglobal.net) Date: Mon, 6 Jul 2009 10:11:32 -0700 (PDT) Subject: [ATM] ATM: Speculum metal Message-ID: <458707.2927.qm@web80501.mail.mud.yahoo.com> Bronze.? Right.? I knew after I sent it I should have looked it up.? Should know better than to trust my memory. Question:? The poor reflectivity of speculum metal:? Is it a characteristic of the metal, or of the casting porosity?? If the latter, an aluminum overcoat would presumably not?improve the reflectivity. The Speculum is, I believe,?a mechanical?device used by gynecologists to inspect female interiors--hence, the giggles.? As far as I know, it?does not lend itself to?mirror making. Eric From stainless_steel at suddenlink.net Tue Jul 7 02:22:46 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 12:22:46 -0500 Subject: [ATM] Fw: Low Pressure Sodium Ballast Message-ID: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> Actually, if you had any panache at all, you would be proud of your country's achievements. They were the first of a new breed (the ships). You can read about them, see movies of them, and download low kilobyte movies of them here: http://www.aht.ndirect.co.uk/ But it's okay, if you are ashamed of what your country has done, and done first, and done best. I can't believe this list is so narrow focused. I guess it is; no one saw my joke, or at least, decided not to comment on it. If Michael wants to unsubscribe me, it's okay. I only have a COUCH for a home, just now. Maybe the rest of my life. I don't give a ____ about your remarks, and I don't give a ____about you. The colonies did right to throw off you NARROW MINDED people. Your king or queen did wrong to let the Royal Airship Works do what they were ordered to doto R-101, one of the miracle aeronautical acheivements of the age. What a narrow minded person you are, to think that ATM-ing touches on only one subject. As was correctly pointed out in the Albert Ingalls ATM books, it touches on all technologies. GODSPEED TO YOU RICHARD! D-LZ130 Please unsubscribe me, Michael. I do not want to be a member of such a narrow minded group. ----- Original Message ----- From: To: "Richard in the UK" Sent: Monday, July 06, 2009 12:02 PM Subject: Re: [ATM] Low Pressure Sodium Ballast > NO. > ----- Original Message ----- > From: "Richard in the UK" > To: "stainless_steel" > Sent: Monday, July 06, 2009 5:23 AM > Subject: Re: [ATM] Low Pressure Sodium Ballast > > >> Hello stainless, >> >> Sunday, July 5, 2009, 11:22:24 PM, you wrote >> >>> Ballast is something (water) that used to be carried in tons and tons >>> and >>> tons of weight in the big rigid airships >> >> I love the old airships, but if I want to read about them I will join >> an airship list. Can you please stop these off topic ramblings? >> >> -- >> Best regards, >> Richard in the UK >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 > 17:54:00 > From stainless_steel at suddenlink.net Tue Jul 7 02:42:19 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 12:42:19 -0500 Subject: [ATM] ATM: Speculum metal In-Reply-To: <458707.2927.qm@web80501.mail.mud.yahoo.com> References: <458707.2927.qm@web80501.mail.mud.yahoo.com> Message-ID: <73C7C5135ECE4945A27098382A2551E6@R101> It did recommend itself to mirror rocommending for half a century. Lord Rossee discovered the spiral nature of galaxis with his 72" specculum mirror at Birr Castle. So, it can't be useless. D-LZ130 ----- Original Message ----- From: To: Sent: Monday, July 06, 2009 12:11 PM Subject: [ATM] ATM: Speculum metal Bronze. Right. I knew after I sent it I should have looked it up. Should know better than to trust my memory. Question: The poor reflectivity of speculum metal: Is it a characteristic of the metal, or of the casting porosity? If the latter, an aluminum overcoat would presumably not improve the reflectivity. The Speculum is, I believe, a mechanical device used by gynecologists to inspect female interiors--hence, the giggles. As far as I know, it does not lend itself to mirror making. Eric _______________________________________________ ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From lowe at nanotechsys.com Tue Jul 7 02:42:57 2009 From: lowe at nanotechsys.com (Jeff Lowe) Date: Mon, 06 Jul 2009 13:42:57 -0400 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: References: Message-ID: <4A5237A1.3060601@nanotechsys.com> From: hermit >Just curious. Enough to ask but not enough to look it up. How narrow >is that band from the LPS light as compared to an LED? LPS is fundamentally the D line pair of sodium, 589 and 859.6 nm. In practice, Low pressure is not No Pressure so there will be some broadening, but should be no more than a few nanometers, depending on the lamp. LEDs on the other hand are quite broad. Typical spectrum on an amber one will have a width of 50-60 nm, rendering them useless for interferometry. -- Jeff Lowe PS, I agree with the comment that this is not an airship list. From arjan.te.marvelde at hetnet.nl Tue Jul 7 02:55:54 2009 From: arjan.te.marvelde at hetnet.nl (Arjan te Marvelde (hetnet)) Date: Mon, 06 Jul 2009 19:55:54 +0200 Subject: [ATM] Stroke and starlap solution. In-Reply-To: References: Message-ID: <4A523AAA.2070001@hetnet.nl> Yes, so I've noticed. My shop changes 20F during the day: it is badly insulated. Best time of year for figuring is cloudy days/nights in the fall. Arjan >>>> Temperature is the biggest culprit in changing figuring results. What I do in the winter is far different than what I do in the summer, and I have an insulated shop that changes temperatures across the seasons maybe 20F! Mel Bartels From vladimir.galogaza1 at zg.t-com.hr Tue Jul 7 03:10:41 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Mon, 6 Jul 2009 20:10:41 +0200 Subject: [ATM] To high pressure References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> Message-ID: <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> Dave, >Please unsubscribe me, Michael. I do not want to be a member >of such a narrow minded group. Making statistics on one sample is not particularly good method. And even this one "sample" just expressed his opinion, and legitimate one. Reaction reflected to much adrenaline, (not bad for the age). Cooled mirror shows less turbulence (just to be on topic). Regards Vladimir. From stainless_steel at suddenlink.net Tue Jul 7 03:08:16 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 13:08:16 -0500 Subject: [ATM] To high pressure In-Reply-To: <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> Message-ID: Thank you, Vladimir. ----- Original Message ----- From: "Vladimir Galogaza" To: "David Harbour" Cc: "ATM List" Sent: Monday, July 06, 2009 1:10 PM Subject: To high pressure > Dave, > >>Please unsubscribe me, Michael. I do not want to be a member >>of such a narrow minded group. > > Making statistics on one sample is not particularly good method. > > And even this one "sample" just expressed his opinion, and legitimate one. > > Reaction reflected to much adrenaline, (not bad for the age). > Cooled mirror shows less turbulence (just to be on topic). > > Regards > Vladimir. > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From stainless_steel at suddenlink.net Tue Jul 7 03:16:11 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 13:16:11 -0500 Subject: [ATM] ATM Wide ranging interests: Message-ID: <367D452938AA4580A65B7848C44B4BB2@R101> If none of you are interested in wider ranger interests, which ATM is about , then count me out. Remove me frome the list, Michael. David From daze39 at earthlink.net Tue Jul 7 03:21:48 2009 From: daze39 at earthlink.net (David Weinshenker) Date: Mon, 06 Jul 2009 11:21:48 -0700 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: <4A5237A1.3060601@nanotechsys.com> References: <4A5237A1.3060601@nanotechsys.com> Message-ID: <4A5240BC.3050402@earthlink.net> Jeff Lowe wrote: > From: hermit >> Just curious. Enough to ask but not enough to look it up. How narrow >> is that band from the LPS light as compared to an LED? > > LPS is fundamentally the D line pair of sodium, 589 and 859.6 nm. In practice, > Low pressure is not No Pressure so there will be some broadening, but should be > no more than a few nanometers, depending on the lamp. LEDs on the other hand are > quite broad. Typical spectrum on an amber one will have a width of 50-60 nm, > rendering them useless for interferometry. I've never been able to catch fringes with LED illumination. Some compact fluorescent bulbs seem to use the blue/green light from the mercury glow directly, with the fluorescent coating mainly filling in a bit of a "continuum" at the long-wavelength side of things; the deep transparent green colored acrylic sheet from TAP Plastics isolates the strong green line quite nicely! Probably starting with a "germicidal UV" bulb (electrically, it's like a fluorescent tube, and would be installed in a similar fixture) with clear glass and no fluorescent coating would work at least as well, and more reliably than finding a suitable fluorescent lamp. (I suspect that the various brands of the latter vary considerably in phosphor emission characteristics; some may have broadband emission in the green or blue as well as the red - I think I lucked out in finding the particular bulb with which I observed this.) -dave w From daze39 at earthlink.net Tue Jul 7 03:47:13 2009 From: daze39 at earthlink.net (David Weinshenker) Date: Mon, 06 Jul 2009 11:47:13 -0700 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <367D452938AA4580A65B7848C44B4BB2@R101> References: <367D452938AA4580A65B7848C44B4BB2@R101> Message-ID: <4A5246B1.8020003@earthlink.net> stainless_steel at suddenlink.net wrote: > If none of you are interested in wider ranger interests, which ATM is about Of course we are! There's more to telescope-making than "pushing glass"! -dave w From jbentz at inreach.com Tue Jul 7 04:06:29 2009 From: jbentz at inreach.com (Jan Bentz) Date: Mon, 06 Jul 2009 12:06:29 -0700 Subject: [ATM] ATM: Speculum metal In-Reply-To: <3e5fde0d0907041523l60dd11cxc53a20bcbae93f72@mail.gmail.com> References: <499941.5078.qm@web82004.mail.mud.yahoo.com> <3e5fde0d0907041523l60dd11cxc53a20bcbae93f72@mail.gmail.com> Message-ID: <4A524B35.8050809@inreach.com> Richard Schwartz wrote: >This tool, what exactly does the ATM do with it? Was the doctor who >named the tool a telescope maker? Back in the 19th century, "doctors" >did lots of strange and interesting things like naturopathy, >homeopathy, chiropractic, and all that stuff whose physical principals >are beyond me. >_______________________________________________ >ATM mailing list http://www.atmlist.net/ > > > Richard -- "The principals are beyond everyone-that's why they are so popular- and belong in the nether regions where a speculum is used." - Websters 3rd Intl. Dict. Jan Bentz From richard1941 at gmail.com Tue Jul 7 04:32:21 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Mon, 6 Jul 2009 12:32:21 -0700 Subject: [ATM] Fw: Low Pressure Sodium Ballast In-Reply-To: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> Message-ID: <7196DD6D-22C4-4B4D-8E34-312F6295CE7F@gmail.com> Don't be so hard on my British bro. The colonies prospered under George II and Pitt, and were proud to be British. Sent from my iPhone On Jul 6, 2009, at 10:22, wrote: > Actually, if you had any panache at all, you would be proud of your > country's achievements. They were the first of a new breed (the > ships). You can read about them, see movies of them, and download > low kilobyte movies of them here: > http://www.aht.ndirect.co.uk/ > > But it's okay, if you are ashamed of what your country has done, and > done first, and done best. I can't believe this list is so narrow > focused. I guess it is; no one saw my joke, or at least, decided not > to comment on it. If Michael wants to unsubscribe me, it's okay. I > only have a COUCH for a home, just now. Maybe the rest of my life. I > don't give a ____ about your remarks, and I don't > give a ____about you. The colonies did right to throw off you NARROW > MINDED people. Your king or queen did wrong to let the Royal Airship > Works do what they were ordered to doto R-101, one of the miracle > aeronautical acheivements of the age. What a narrow minded person > you are, to think that ATM-ing touches on only one subject. As was > correctly pointed out in the Albert Ingalls ATM books, it touches on > all technologies. > > GODSPEED TO YOU RICHARD! > > D-LZ130 > > Please unsubscribe me, Michael. I do not want to be a member of such > a narrow minded group. > > ----- Original Message ----- From: > To: "Richard in the UK" > Sent: Monday, July 06, 2009 12:02 PM > Subject: Re: [ATM] Low Pressure Sodium Ballast > > >> NO. >> ----- Original Message ----- From: "Richard in the UK" > > >> To: "stainless_steel" >> Sent: Monday, July 06, 2009 5:23 AM >> Subject: Re: [ATM] Low Pressure Sodium Ballast >> >> >>> Hello stainless, >>> >>> Sunday, July 5, 2009, 11:22:24 PM, you wrote >>> >>>> Ballast is something (water) that used to be carried in tons and >>>> tons and >>>> tons of weight in the big rigid airships >>> >>> I love the old airships, but if I want to read about them I will >>> join >>> an airship list. Can you please stop these off topic ramblings? >>> >>> -- >>> Best regards, >>> Richard in the UK >>> >>> _______________________________________________ >>> ATM mailing list http://www.atmlist.net/ >> >> >> --- >> --- >> --- >> --- >> -------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17 >> :54:00 > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From vladimir.galogaza1 at zg.t-com.hr Tue Jul 7 04:59:24 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Mon, 6 Jul 2009 21:59:24 +0200 Subject: [ATM] Low Pressure Sodium Ballast References: <4A5237A1.3060601@nanotechsys.com> <4A5240BC.3050402@earthlink.net> Message-ID: >Probably starting with a "germicidal UV" bulb (electrically, >it's like a fluorescent tube, and would be installed in a >similar fixture) with clear glass and no fluorescent coating >would work at least as well, Another suitable UV lamp is the one used for illuminating photoresist in manufacturing of printed circuits. It is similar to germicidal lamp but smaller, cca 30 cm long and 2 cm diameter. Requires ballast. Regards Vladimir. From rmay at nethere.com Tue Jul 7 05:01:37 2009 From: rmay at nethere.com (Bob May) Date: Mon, 6 Jul 2009 13:01:37 -0700 Subject: [ATM] Low Pressure Sodium Ballast References: <4A515F3F.106@verizon.net> <8DF1772168B3472B8D8920FD77942575@HELENYLCMWAV95> Message-ID: <001201c9fe74$92a63f80$2a995545@amd> 12VDC just means a wallwart PS for the power. Maybe not quite as efficient but not hard to do. 1A test power supplies aren't that expensive for the cheap ones and a battery charger also works for more power. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From richard1941 at gmail.com Tue Jul 7 05:12:14 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Mon, 6 Jul 2009 13:12:14 -0700 Subject: [ATM] To high pressure In-Reply-To: <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> Message-ID: <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> I would urge the list overlord to deny Mr. Harbour's request because he knows too much about telescopery to let go. Sent from my iPhone On Jul 6, 2009, at 11:10, "Vladimir Galogaza" wrote: > Dave, > >> Please unsubscribe me, Michael. I do not want to be a member of >> such a narrow minded group. > > Making statistics on one sample is not particularly good method. > > And even this one "sample" just expressed his opinion, and > legitimate one. > > Reaction reflected to much adrenaline, (not bad for the age). > Cooled mirror shows less turbulence (just to be on topic). > > Regards > Vladimir. > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From rmay at nethere.com Tue Jul 7 05:22:01 2009 From: rmay at nethere.com (Bob May) Date: Mon, 6 Jul 2009 13:22:01 -0700 Subject: [ATM] Low Pressure Sodium Ballast References: <4A5237A1.3060601@nanotechsys.com> <4A5240BC.3050402@earthlink.net> Message-ID: <002901c9fe77$6cacd840$2a995545@amd> The light from a flourscent bulb is several lines from a ruddy orange to blue. From my experience, there are basically two kinds of lights aside from cool white, warm white and so forth. Some are just the lines themselves from high efficiency phosphors (the kind desired) and the ones with a low efficiency broadband phosphors in addition (less desirable). The first type can produce fringes easily without any filters but you get purple and green fringes. The second type will produce fringes but they will be very faint. Putting a strong green filter on either improves the contrast of the lines immensely. I recommend that you wander about with a piece of grating to look at the spectrum of the various flourscent lights about. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From richard at foucault.co.uk Tue Jul 7 06:10:21 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Mon, 6 Jul 2009 22:10:21 +0100 Subject: [ATM] To high pressure In-Reply-To: <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> Message-ID: <182792747.20090706221021@foucault.co.uk> Hello Richard, Monday, July 6, 2009, 9:12:14 PM, you wrote: > I would urge the list overlord to deny Mr. Harbour's request because > he knows too much about telescopery to let go. The list overlord doesn't need to take any action, Mr. Harbour is quite able to remove himself if he wishes, as I am sure he is aware. -- Best regards, Richard in the UK From stainless_steel at suddenlink.net Tue Jul 7 06:16:02 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 16:16:02 -0500 Subject: [ATM] To high pressure In-Reply-To: <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> Message-ID: Thank you, flying wing man. (and other friends) ----- Original Message ----- From: "Richard Schwartz" To: "Vladimir Galogaza" Cc: "David Harbour" ; "ATM List" Sent: Monday, July 06, 2009 3:12 PM Subject: Re: [ATM] To high pressure >I would urge the list overlord to deny Mr. Harbour's request because > he knows too much about telescopery to let go. > > Sent from my iPhone > > On Jul 6, 2009, at 11:10, "Vladimir Galogaza" > > wrote: > >> Dave, >> >>> Please unsubscribe me, Michael. I do not want to be a member of >>> such a narrow minded group. >> >> Making statistics on one sample is not particularly good method. >> >> And even this one "sample" just expressed his opinion, and >> legitimate one. >> >> Reaction reflected to much adrenaline, (not bad for the age). >> Cooled mirror shows less turbulence (just to be on topic). >> >> Regards >> Vladimir. >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From stainless_steel at suddenlink.net Tue Jul 7 06:19:43 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 16:19:43 -0500 Subject: [ATM] ATM: Joke Message-ID: <2E8FA62B29464A6DB962A468879CCA71@R101> I made a joke, albeit a rather long one. No one got it. Does anyone have a sense of humor here? (No insult intended- did no one understand my joke about ballast/lightness?) D-LZ130 From daze39 at earthlink.net Tue Jul 7 06:33:10 2009 From: daze39 at earthlink.net (David Weinshenker) Date: Mon, 06 Jul 2009 14:33:10 -0700 Subject: [ATM] word origins \ Re: ATM: Joke In-Reply-To: <2E8FA62B29464A6DB962A468879CCA71@R101> References: <2E8FA62B29464A6DB962A468879CCA71@R101> Message-ID: <4A526D96.5020505@earthlink.net> stainless_steel at suddenlink.net wrote: > I made a joke, albeit a rather long one. No one got it. Does anyone have a > sense of humor here? (No insult intended- did no one understand my joke > about ballast/lightness?) I was mainly thinking of the way word origins link back: "ballast" as something that holds something down, whether it be the ascent of an airship that would be otherwise more buoyant than necessary - or the current in an electric discharge. (The original "ballast coil" for a fluorescent lamp was in fact a series inductance to stabilize the current; the term has been kept in the electrical goods trade as a generic word for "that thing that goes in the circuit between the power line and the actual lamp electrodes", even though it may these days be a specialized transformer or solid-state power converter!) Similarly, a "speculum" is "something to look with" - in addition to the medical implement previously mentioned, it is also an archaic synonym for "mirror" - and thus "speculum metal" was the name given to the alloys developed for solid metal mirrors. -dave w From stainless_steel at suddenlink.net Tue Jul 7 06:32:39 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 16:32:39 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer Message-ID: <3D7E3AF2D9724288AD541883FE992C17@R101> So what what the literature says. Were you there? Did someone not sneak in a foucault test? Was there always a camera on them? Did not someone sneak in another test? Tell me you know for sure that this is the case, that no one ever did another kind of test on them? D-LZ130 P.S. I know for a fact that Hubble made major discoveries made my Cassegrain system using an autocollimation null test. Sorry. (After he made a foucault test on a primary). BY RITCHEY. ----- Original Message ----- From: To: "Vladimir Galogaza" ; "Bob May" Cc: "ATM List" Sent: Thursday, June 18, 2009 12:02 PM Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > Sorry, disagree. The big discoveries (even by Hubble) were made with > mirrors using Hartmann, Focault, and Null testing on the stars. > > Sorry. > > D-LZ130 > > > ----- Original Message ----- > From: "Vladimir Galogaza" > To: "Bob May" > Cc: "ATM List" > Sent: Thursday, June 18, 2009 2:38 AM > Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > > >>I am going to comment some of Bob's statements about suitability of >> Bath interferometry for one time ATM. >> >> That Bath equipment is not in everybody's pile of junk is true because >> people pile up what they think can be useful. Since Bath interferometer >> still has not reached the status of the useful tool by "almost everybody" >> almost nobody is collecting its components. And they are: >> 1.) keychain laser pointer ( I believe that every single ATM has at least >> one). >> 2.) beam splitter cube >> 3.) Small ( 5x 5 mm) front surface flat mirror. >> 3.) small biconvex lens ( diameter about 5-10 mm, FL about 10 to 15 mm) >> 4.) webcam or digital camera >> 5.) optional xyz translational stage without readout >> >> The result of assembling an interferometer from those parts is superior >> to anything used so far by ATMs to measure the mirror quality. >> >> Building Foucault (with usual micrometer readout) is by no means simpler >> or essentially cheaper than building Bath interferometer from mentioned >> components. >> Bath interferometer is small item, can fit in a less than 10 x 10 x10 cm >> space. >> Understanding how Bath interferometer works is actualy easier than >> how Foucault realy works ( in wave optics terms) . >> >> Building entire telescope is so much more difficult task than building >> Bath >> interferometer >> that for any ATM there is no excuse not to attempt one by claiming that >> it >> is out of >> reach for ATM. (Unfortunately, many ATMs try to avoid even Foucault and >> settle for Ronchi). >> >> Contrary to assertion, Bath setup needs not to be especially accurately >> done, >> in any case required accuracy is similar to Foucault tester and by far >> less >> than >> required mirror figure or OTA. >> My interferometer is witnessing that every ATM under the sky can do it >> with >> minimal skill or tools. >> >> Contrary to assertion, it is proved that webcams can do it. Image >> resolution >> above half megapixel is not required. Mentioned high megapixel cameras >> are >> not required for their megapixels but for their manual mode of operation. >> And >> some of the best interferograms made by ATMs on the list are made with >> compact digital camera (like Gert did superbly). >> >> As a final remarque, somebody daring attempting the one millionth of inch >> accurate >> figuring should not be scared off by comparably trivial requirements of >> Bath >> interferometry. >> (Per aspera ad astra) >> >> Regards >> Vladimir. >> >> ----- Original Message ----- >> From: "Bob May" >> To: >> Sent: Wednesday, June 17, 2009 10:51 PM >> Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer >> >> >>>I too think that the Bath Interfrometer is a nice tool. HOWEVER, >>> it does take some equipment that isn't in almost everybody's pile >>> of junk. The laser is a bit dicy, the beam splitter is also not >>> cheap (anything over $20 is expensive for the casual amateur >>> mirror maker) and the setup needs to be accurately done or theere >>> is no reults to deal with. IN addition, cheap webcams and video >>> (an expensive item all by themselves) really don't do that good >>> of a job at reading the results for the accuracy that the test >>> can resolve. A high megapixel camera is a lot better device to >>> record the image. >>> As such, I put that method of determining the mirror's shape out >>> of the reach of the one time mirror maker, of which a fair number >>> of people are. It is useful for a large class on mirror making >>> to give a final result of a particular mirror that was made tho. >>> Bob May >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: 06/18/09 > 05:53:00 > s From stainless_steel at suddenlink.net Tue Jul 7 06:34:29 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 16:34:29 -0500 Subject: [ATM] To high pressure In-Reply-To: <182792747.20090706221021@foucault.co.uk> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101><0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e><76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> <182792747.20090706221021@foucault.co.uk> Message-ID: <9B5A31C7810A450D9BCA55A850FF8047@R101> Thanks, Richard. Maybe the list could survive without you also. D-LZ130 ----- Original Message ----- From: "Richard in the UK" To: "Richard Schwartz" Sent: Monday, July 06, 2009 4:10 PM Subject: Re: [ATM] To high pressure > Hello Richard, > > Monday, July 6, 2009, 9:12:14 PM, you wrote: > >> I would urge the list overlord to deny Mr. Harbour's request because >> he knows too much about telescopery to let go. > > The list overlord doesn't need to take any action, Mr. Harbour is > quite able to remove himself if he wishes, as I am sure he is aware. > > -- > Best regards, > Richard in the UK > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From lenses at roadrunner.com Tue Jul 7 07:21:35 2009 From: lenses at roadrunner.com (lenses at roadrunner.com) Date: Mon, 6 Jul 2009 18:21:35 -0400 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <4A5246B1.8020003@earthlink.net> Message-ID: <20090706222135.WTWHY.341075.root@cdptpa-web26-z02> Sure am interested in "everything" Sometimes I break glass :) ---- David Weinshenker wrote: > stainless_steel at suddenlink.net wrote: > > If none of you are interested in wider ranger interests, which ATM is about > > Of course we are! There's more to telescope-making > than "pushing glass"! > > -dave w > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From stainless_steel at suddenlink.net Tue Jul 7 07:26:59 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 17:26:59 -0500 Subject: [ATM] word origins \ Re: ATM: Joke In-Reply-To: <4A526D96.5020505@earthlink.net> References: <2E8FA62B29464A6DB962A468879CCA71@R101> <4A526D96.5020505@earthlink.net> Message-ID: <22AF4AB9C36441EDA823F62D98A7D358@R101> Thank you, David. D-LZ130 ----- Original Message ----- From: "David Weinshenker" To: "ATM list" Sent: Monday, July 06, 2009 4:33 PM Subject: [ATM] word origins \ Re: ATM: Joke > stainless_steel at suddenlink.net wrote: >> I made a joke, albeit a rather long one. No one got it. Does anyone have >> a >> sense of humor here? (No insult intended- did no one understand my joke >> about ballast/lightness?) > > I was mainly thinking of the way word origins link back: "ballast" as > something > that holds something down, whether it be the ascent of an airship that > would > be otherwise more buoyant than necessary - or the current in an electric > discharge. > (The original "ballast coil" for a fluorescent lamp was in fact a series > inductance > to stabilize the current; the term has been kept in the electrical goods > trade as a > generic word for "that thing that goes in the circuit between the power > line and the > actual lamp electrodes", even though it may these days be a specialized > transformer > or solid-state power converter!) > > Similarly, a "speculum" is "something to look with" - in addition to the > medical > implement previously mentioned, it is also an archaic synonym for > "mirror" - and > thus "speculum metal" was the name given to the alloys developed for solid > metal > mirrors. > > -dave w > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From stainless_steel at suddenlink.net Tue Jul 7 07:30:53 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 17:30:53 -0500 Subject: [ATM] ATM: Joke In-Reply-To: References: <2E8FA62B29464A6DB962A468879CCA71@R101> Message-ID: <2761F7A04038426DA4FF00FDE320C221@R101> Thanks, Pete. I actually never knew why they called them ballast tubes. It just didn't make sense; it does now, thanks to guys like you. D-LZ130 ----- Original Message ----- From: "Pete McDonald" To: Cc: Sent: Monday, July 06, 2009 5:02 PM Subject: Re: [ATM] ATM: Joke >I have been a member of this list for many years, at least 15. I have >never > posted before, and now I am goaded enough that I can't passively stand by > and see one of my favorite teacher vilified. All knowledge is related to > ATM. When DLZ 130 made his post about ballast, he stated his understanding > of ballast by the mechanical definition. He proceeded to cite an example > based on his knowledge of airship design. Then he posed the question, "how > does the word ballast relate to electrical application." Nobody as yet has > answered his question. Great teachers use this method of stating an > example, > seemingly unrelated, and then asking a question to stimulate the thinking > of > their students. Cross cultivation of the different branches of the > sciences > has caused each to advance. I tend to think that Davey already knows the > answer to his question. His question was meant, it seems to me, to > stimulate inquiry and to edify by the responses to the question, all who > don't know. > > -------------------------------------------------- > From: > Sent: Monday, July 06, 2009 5:19 PM > To: "ATM list" > Subject: [ATM] ATM: Joke > >> I made a joke, albeit a rather long one. No one got it. Does anyone have >> a >> sense of humor here? (No insult intended- did no one understand my joke >> about ballast/lightness?) >> >> D-LZ130 >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From stainless_steel at suddenlink.net Tue Jul 7 07:34:02 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 6 Jul 2009 17:34:02 -0500 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <20090706222135.WTWHY.341075.root@cdptpa-web26-z02> References: <20090706222135.WTWHY.341075.root@cdptpa-web26-z02> Message-ID: Baerings, axles, machining, woodwork- the list could go on and on. http://www.atmsite.org/contrib/Harbour/index.html Thanks, Dave. Dave (P.S. I have even devised a drive that uses wind power; regulation of rpm is the secret.) ----- Original Message ----- From: To: "ATM list" Sent: Monday, July 06, 2009 5:21 PM Subject: Re: [ATM] ATM Wide ranging interests: > Sure am interested in "everything" > Sometimes I break glass > :) > > ---- David Weinshenker wrote: >> stainless_steel at suddenlink.net wrote: >> > If none of you are interested in wider ranger interests, which ATM is >> > about >> >> Of course we are! There's more to telescope-making >> than "pushing glass"! >> >> -dave w >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 From b-hamburger at artinso.com Tue Jul 7 07:40:37 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Tue, 7 Jul 2009 00:40:37 +0200 Subject: [ATM] Bath interferometer Message-ID: <02f301c9fe8a$c9e43d10$5dacb730$@com> Vladimir, What would be the quality requirements of the components for a bath interferometer. Could you share with us the components and setup you use? I looked on surplus shed and they have everything needed in different price ranges. In particular, what would be the requirements for a beam-splitter. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com From martti.koskimo at kolumbus.fi Tue Jul 7 07:54:13 2009 From: martti.koskimo at kolumbus.fi (Martti Koskimo) Date: Tue, 7 Jul 2009 01:54:13 +0300 Subject: [ATM] Stroke and starlap solution. In-Reply-To: <4A523AAA.2070001@hetnet.nl> Message-ID: Very effective solution to the temperature problems has been polishing slurry circulation. Any cheap pump will do. I use in all polishing and figuring machines pumps made for milling lubricant. Using cheap AGUARIUM THERMOSTAT you can keep slurry and pitch temperature always +- 0.5 degrees from the desired although the shop temperature is 10 degrees colder. The whole lubricant circulation and thermostat cost has been about 100 $ / unit Martti Koskimo -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Arjan te Marvelde (hetnet) Sent: 6. hein?kuuta 2009 20:56 To: atm at atmlist.net Subject: Re: [ATM] Stroke and starlap solution. Yes, so I've noticed. My shop changes 20F during the day: it is badly insulated. Best time of year for figuring is cloudy days/nights in the fall. Arjan >>>> Temperature is the biggest culprit in changing figuring results. What I do in the winter is far different than what I do in the summer, and I have an insulated shop that changes temperatures across the seasons maybe 20F! Mel Bartels _______________________________________________ ATM mailing list http://www.atmlist.net/ From atmpob at yahoo.com Tue Jul 7 07:57:00 2009 From: atmpob at yahoo.com (Dale Eason) Date: Mon, 6 Jul 2009 15:57:00 -0700 (PDT) Subject: [ATM] Bath interferometer Message-ID: <626280.46756.qm@web54502.mail.re2.yahoo.com> See the wiki at: http://starryridge.com/mediawiki-1.9.1/index.php?title=Bath_Interferometer It should answer all of your questions. The short answer is that the optical figure of the splitter and lens matters little because the beam passes through them in both directions and error are canceled. Thus just about any of the splitters will do. The smaller ones are prefered for reasons explained in the wiki. The is also a yahoo group dedicated to interferometry and the Bath is usually the major topic. Yahoo group interferometry. Dale Eason --- On Mon, 7/6/09, Berthold Hamburger wrote: > From: Berthold Hamburger > Subject: [ATM] Bath interferometer > To: atm at atmlist.net > Date: Monday, July 6, 2009, 5:40 PM > Vladimir, > > > > What would be the quality requirements of the components > for a bath > interferometer. Could you share with us the components and > setup you use? I > looked on surplus shed and they have everything needed in > different price > ranges. In particular, what would be the requirements for a > beam-splitter. > > > > Berthold > > -- > > Berthold Hamburger - Cellist/Spain > > Email: behambu at artinso.com > > http://www.artinso.com > > http://www.astro.artinso.com > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mjc5 at psu.edu Tue Jul 7 08:22:28 2009 From: mjc5 at psu.edu (Mike Coslo) Date: Mon, 06 Jul 2009 19:22:28 -0400 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <367D452938AA4580A65B7848C44B4BB2@R101> References: <367D452938AA4580A65B7848C44B4BB2@R101> Message-ID: <4A528734.2050004@psu.edu> stainless_steel at suddenlink.net wrote: > If none of you are interested in wider ranger interests, which ATM is > about , then count me out. > > Remove me frome the list, Michael. Ahem.... umm, this is when cooler heads are supposed to prevail guys. Out of the pool kids! Now step back, have a glass of your favorite beverage, be it Earl Grey tea or a Boilermaker, and relax for the evening. Everyone will be in better spirits in the morning. Failing that, the floggings will continue until morale improves ;^) - Mike - From wkitty42 at windstream.net Tue Jul 7 08:54:35 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Mon, 06 Jul 2009 19:54:35 -0400 Subject: [ATM] To high pressure In-Reply-To: <182792747.20090706221021@foucault.co.uk> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> <182792747.20090706221021@foucault.co.uk> Message-ID: <4A528EBB.3020303@windstream.net> Richard in the UK wrote: > Hello Richard, > > Monday, July 6, 2009, 9:12:14 PM, you wrote: > >> I would urge the list overlord to deny Mr. Harbour's request because >> he knows too much about telescopery to let go. > > The list overlord doesn't need to take any action, Mr. Harbour is > quite able to remove himself if he wishes, as I am sure he is aware. agreed, agreed, agreed :LOL: especially since each and every post from the list contains the address to the list's website where one can manage their account all by themselves ;) From wkitty42 at windstream.net Tue Jul 7 08:56:00 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Mon, 06 Jul 2009 19:56:00 -0400 Subject: [ATM] ATM: Joke In-Reply-To: <2E8FA62B29464A6DB962A468879CCA71@R101> References: <2E8FA62B29464A6DB962A468879CCA71@R101> Message-ID: <4A528F10.5050001@windstream.net> stainless_steel at suddenlink.net wrote: > I made a joke, albeit a rather long one. No one got it. Does anyone have > a sense of humor here? (No insult intended- did no one understand my > joke about ballast/lightness?) personally? i got the joke about the ballast schtuffings but the overall sidestream was... ummm... "over the top" which is what triggered the "please don't do that" response from another list member ;) From atmer at flash.net Tue Jul 7 09:25:54 2009 From: atmer at flash.net (Anthony Stillman) Date: Mon, 6 Jul 2009 17:25:54 -0700 (PDT) Subject: [ATM] ATM: Joke Message-ID: <749844.17018.qm@web82006.mail.mud.yahoo.com> You may be an ATM, no wait, you ARE an ATM if: You have ever made a telescope out of: Drug store reading glasses (in the store) Ice Hot glue Metal Rock ... Friends with glass coffee tables no longer invite you over. While some people see the glass as half full and other people see it as half empty, you see a lens blank that needs edging. Anthony I'd rather be pushing glass. From mjc5 at psu.edu Tue Jul 7 09:45:41 2009 From: mjc5 at psu.edu (Mike Coslo) Date: Mon, 06 Jul 2009 20:45:41 -0400 Subject: [ATM] ATM: Speculum metal In-Reply-To: <73C7C5135ECE4945A27098382A2551E6@R101> References: <458707.2927.qm@web80501.mail.mud.yahoo.com> <73C7C5135ECE4945A27098382A2551E6@R101> Message-ID: <4A529AB5.4040800@psu.edu> stainless_steel at suddenlink.net wrote: > It did recommend itself to mirror rocommending for half a century. > > Lord Rossee discovered the spiral nature of galaxis with his 72" > specculum mirror at Birr Castle. So, it can't be useless. We are amateurs, and we are not constrained by others as to what we make. Speculum metal is just as valid a way to make a mirror as if I were to make one of those incredibly impractical simple lens objective lens, no tube telescopes that require an army of helpers. Its a part of history. And it is very, very cool. Personally speaking, I would be much more impressed by a working model of say Newton's original reflector, made with historical processes and materials, than with say, the way I made my scope. It seems that we sometimes fall into a trap of orthodoxy. Somehow, some way a certain type of telescope becomes the fashion of the moment, and then tends to dominate. Sometimes ultra thin, ultra lightweight, ultra fast, ultra something or other. They are all good. But then again, so is my full thickness mirror. Same goes for the way we make out telescopes. As soon as the finished product remembers how it was made, we should make that the only way that a scope should be made. Oddly enough, we can fall into fashions also. Fashions are just that-fashions. I don't like the way that Tex says to make polishing tools, but If someone wants to do it, great. Heck if someone wants to use the St. Gobain method of annealing a mirror, then let 'em have at it. I might say it stinks, but for other reasons than trying to discourage him - the method does indeed stink. We as Amateur telescope makers, are not constrained by the fashion, or by the newness or latest and greatest. That is a good thing actually, as the latest and greatest are not in the ability of most of us to produce, we don't have the resources. Then we'd just sit around BS'ing like armchair astronomers do. Just sayin'-Mike - From gary at gfphoto.com Tue Jul 7 12:26:56 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Mon, 06 Jul 2009 23:26:56 -0400 Subject: [ATM] To high pressure In-Reply-To: <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> References: <61E7EB5B064D42A8B4BDDE23EC8CA885@R101> <0B4CF9391FC143DC85219FD1856FE706@piv555a133b59e> <76D5F441-1F95-4FDE-8522-971ABB7A4C17@gmail.com> Message-ID: <4A52C080.4050207@gfphoto.com> Richard Schwartz wrote: > I would urge the list overlord to deny Mr. Harbour's request because > he knows too much about telescopery to let go. > Ditto... "telescopery" - is that one of those medieval practices that was banned in the colonies? Gary Fuchs From rmay at nethere.com Tue Jul 7 14:09:46 2009 From: rmay at nethere.com (Bob May) Date: Mon, 6 Jul 2009 22:09:46 -0700 Subject: [ATM] ATM Wide ranging interests: References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu> Message-ID: <002e01c9fec1$25eb7160$3dff1345@amd> I don't have any more glasses floating about, they have all been turned into small telescopes. My next door neighbor doesn't understand why I feel the need for large diameter glasses and when I tell her I've got aperture fever, she has no idea of what I'm saying. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From vorblesnak at peak.org Tue Jul 7 14:13:18 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Mon, 6 Jul 2009 22:13:18 -0700 (PDT) Subject: [ATM] Shot myself in the foot again .. Message-ID: <53042.4.242.141.110.1246943598.squirrel@webmail.peak.org> The other day when I was testing the tessellated mirror I noticed that the glass was very thin, maybe 1 or 2 millimeters at most. I commented that I was getting a reflection from the back of the mirror that was almost as bright as the front. Today in the mail I got the glued blank back from Bob May. He had been unable to figure it due to adhesive problems. So, two sorta mirrors, I whipped up two mounts and went hunting for a star to test. I got a bright yellowish star, kind of southwest of zenith and Vega. The tessellated mirror actually did better than the single glass but both of them need work. They also need coated as there was a big halo of wild light around them from the back reflection. I should have remembered as the same thing got me when I was testing the 16 inch ultrathin. There was always this greenish sort of nebula where ever I looked. I ended up grinding the back of that glass to get rid of the back reflection. Can't grind this glass, it is under everything. So I'm back to square one. I will figure as well as I can using ronchi etc. and then coat it for the star test. David From wkitty42 at windstream.net Tue Jul 7 14:56:34 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Tue, 07 Jul 2009 01:56:34 -0400 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <002e01c9fec1$25eb7160$3dff1345@amd> References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu> <002e01c9fec1$25eb7160$3dff1345@amd> Message-ID: <4A52E392.3030503@windstream.net> Bob May wrote: > I don't have any more glasses floating about, they have all been > turned into small telescopes. My next door neighbor doesn't > understand why I feel the need for large diameter glasses and > when I tell her I've got aperture fever, she has no idea of what > I'm saying. yer lucky she/they haven't called the policia on yaz fer that!! :) ;) From brian.itsi at gmail.com Tue Jul 7 20:01:33 2009 From: brian.itsi at gmail.com (Brian Karlsen) Date: Tue, 7 Jul 2009 13:01:33 +0200 Subject: [ATM] refractor clarification In-Reply-To: <7b48d05a0907050337o16747e74madcc81e6c1ad00f2@mail.gmail.com> References: <338084.41947.qm@web35803.mail.mud.yahoo.com> <7b48d05a0907050337o16747e74madcc81e6c1ad00f2@mail.gmail.com> Message-ID: <7b48d05a0907070401s494d2fb8ka890d905a9d33078@mail.gmail.com> I was about to order the parts for the scope from surplus shed when I noticed the lenses in my previous post don't actually say they are achromatic they say they are air spaced glass doublet objective lens Item No: L3002 and L2196 I found one that specified it is a achromatic Item No: L3911 but it says it is a binocular objective FL 350mm they are all the same diameter but now I am not sure what to get my mother has agreed to pay for all the components for me as it is my birthday on Sunday and im keen to get the bits to start puting together my scope but now I am confused which lens should I get all these parts are in my wishlist to find them easier under this email address brian.itsi at gmail.com On Sun, Jul 5, 2009 at 12:37 PM, Brian Karlsen wrote: > thanks guys for the advice I was hoping that with the longer focal ratios > and bigger aperture that I would be able to better the performance of the > store scope but maybe I was just fooling myself looking at the acromatics > they are quite a bit more expencive for the same apature so I think ill > wait a couple more months and save up for them as I dont whant to end up > with a big scope with so much abiration that it isnt useable. > > I have wondered about those difragm's I have seen sites where ppl have put > them in but havent found discription on what they are for or how they work > > the new lenses I found are 80mm 400 fl and 80mm 900mm fl both achromatic > which would be a more useful lens I am thinking the 400 as I would like a > brighter image as I want to use it for astrofitography as well I used to use > my binoculars with the camera mounted to it fo photographing birds and ships > at sea > > > From b-hamburger at artinso.com Tue Jul 7 21:06:39 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Tue, 7 Jul 2009 14:06:39 +0200 Subject: [ATM] Bath interferometer and Ross In-Reply-To: <626280.46756.qm@web54502.mail.re2.yahoo.com> References: <626280.46756.qm@web54502.mail.re2.yahoo.com> Message-ID: <031401c9fefb$636c7b30$2a457190$@com> Thank you for the excellent link. I also joined the list. Ceravolo has some good information on his site also. Speaking of which, I would like to inquire about the feasibility of making a useable ROSS lens with standard ATM techniques and testing equipment. Has someone succeeded in doing so? Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: Dale Eason [mailto:atmpob at yahoo.com] > Sent: martes, 07 de julio de 2009 0:57 > To: atm at atmlist.net; Berthold Hamburger > Subject: Re: [ATM] Bath interferometer > > > See the wiki at: > http://starryridge.com/mediawiki- > 1.9.1/index.php?title=Bath_Interferometer > > It should answer all of your questions. The short answer is that the > optical figure of the splitter and lens matters little because the beam > passes through them in both directions and error are canceled. Thus > just about any of the splitters will do. The smaller ones are prefered > for reasons explained in the wiki. > > The is also a yahoo group dedicated to interferometry and the Bath is > usually the major topic. Yahoo group interferometry. > > Dale Eason > > > --- On Mon, 7/6/09, Berthold Hamburger wrote: > > > From: Berthold Hamburger > > Subject: [ATM] Bath interferometer > > To: atm at atmlist.net > > Date: Monday, July 6, 2009, 5:40 PM > > Vladimir, > > > > > > > > What would be the quality requirements of the components > > for a bath > > interferometer. Could you share with us the components and > > setup you use? I > > looked on surplus shed and they have everything needed in > > different price > > ranges. In particular, what would be the requirements for a > > beam-splitter. > > > > > > > > Berthold > > > > -- > > > > Berthold Hamburger - Cellist/Spain > > > > Email: behambu at artinso.com > > > > http://www.artinso.com > > > > http://www.astro.artinso.com > > > > > > > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > > > > From richard at foucault.co.uk Tue Jul 7 21:42:14 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Tue, 7 Jul 2009 13:42:14 +0100 Subject: [ATM] Bath interferometer and Ross In-Reply-To: <031401c9fefb$636c7b30$2a457190$@com> References: <626280.46756.qm@web54502.mail.re2.yahoo.com> <031401c9fefb$636c7b30$2a457190$@com> Message-ID: <6410400793.20090707134214@foucault.co.uk> Hello Berthold, Tuesday, July 7, 2009, 1:06:39 PM, you wrote: > Speaking of which, I would like to inquire about the feasibility of making a > useable ROSS lens with standard ATM techniques and testing equipment. Before you do that, may I suggest you have a read about the Offner null test?. It has the advantage of using two off the shelf decent quality BCX lenses. Very useful tool for this test (and many other optical bench setups) is a "stick micrometer" for accurately setting distances between elements. If you are not familiar with a stick micrometer, it is an internal type mic, i.e. it measures between two faces, but with combination of many precision spacers, it will measure a wide range. I picked one up that does 5 inches (127mm) to 20 feet (6 meters) to a resolution of better than half a thou (0.01mm) -- Best regards, Richard in the UK From mjc5 at psu.edu Tue Jul 7 23:06:50 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Tue, 07 Jul 2009 10:06:50 -0400 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <4A52E392.3030503@windstream.net> References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu> <002e01c9fec1$25eb7160$3dff1345@amd> <4A52E392.3030503@windstream.net> Message-ID: <48FCA995-9C88-4144-ABB1-7BD2544229FB@psu.edu> On Jul 7, 2009, at 1:56 AM, waldo kitty wrote: > Bob May wrote: >> I don't have any more glasses floating about, they have all been >> turned into small telescopes. My next door neighbor doesn't >> understand why I feel the need for large diameter glasses and >> when I tell her I've got aperture fever, she has no idea of what >> I'm saying. > > yer lucky she/they haven't called the policia on yaz fer that!! :) ;) Cymbal crash! Now I have to explain to my co-workers why I just sent coffee through my nose! Best laugh I had in a long time, but now I have to get more coffee... 8^) -73 de Mike N3LI - From gfbrandenburg at yahoo.com Tue Jul 7 23:25:37 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Tue, 7 Jul 2009 07:25:37 -0700 (PDT) Subject: [ATM] refractor clarification Message-ID: <241997.17982.qm@web111504.mail.gq1.yahoo.com> Here is one way. Don't know if the images will come through: What we finally decided to do was to send me on a 3-hour drive over Easter weekend to Surplus Shed in the tiny town of Fleetwood, PA (about a dozen miles northeast of Reading) to look for inexpensive, but decent-quality, achromatic doublets and eyepieces. My plan was to install the lenses into tubes made of various pieces of plastic PVC pipe. With the help of the staff at Surplus Shed, I purchased two dozen cemented doublet lenses with a diameter of 52 millimeters and a focal length of 220 mm, which is pretty ?fast? for achromats. To go with the objective lenses, I also purchased enough 20-mm and 12-mm 0.965? eyepieces so that each student would get one of each. The eyepieces only cost $3.75 each. So far, the total price of the optics, for each scope, was $13.50. The normal retail price for these things, if purchased new from a standard optical store, would probably be an order of magnitude greater. ? For the sake of historical authenticity, I also decided to get about four singlet convex objective lenses of the type that Galileo used, along with smaller concave lenses to use as eyepieces. The lenses cost four dollars each, or $8 per scope. ? If you?ve never been to Surplus Shed, and you like to make astronomical stuff, then you definitely need to go for a visit some Friday! It?s a former school building that is stocked from basement to attic with all sorts of lenses, eyepieces, micrometers, tubes, pieces of telescopes, electronic odds and ends, and other surplus stuff that they have picked up from a variety of sources. To be frank, the place is a bit on the cluttered side, and you can?t even go in the front door. But the staff there was very friendly, and they gave me a lot of assistance, suggestions and encouragement on choosing lenses that would fit into various types of PVC pipe and would not be hard for the students to use. Once I had decided on the type of objective lens we would use, I had to take about half an hour to pick out the two dozen lenses that I thought were in the best shape. ? When I got back home, I still had to figure out how to get from a nominal 2-inch inner diameter PVC tube, which would hold the objective lens securely, to a 1-inch inner diameter PVC tube, in such a way that the components would be held steady, but students could slide something in and out to focus on near or distant objects. I took my problem to my local Brookland Servicestar Hardware store, and one of the veteran salespeople immediately solved it. I needed a PVC 2-inch to one-and-a-half inch reducer, followed by a PVC one-and-a-half inch to one-and-a-quarter inch junction, followed by a piece of 1?? PVC pipe. Inside that, we would slide a piece of one-inch PVC pipe which had an outside diameter that was almost, but not quite, 1.25 inches. A few layers of masking tape would build up the outer diameter of the last one-inch PVC pipe so that it would fit snugly inside the 1? ?inch pipe and allow the student to slide it back and forth for the purpose of focusing. The 0.965-inch outer diameter eyepieces would also need a few layers of masking tape so that they would fit into the one-inch tubing. Finally, to protect and shade the achromatic objective, a two-inch to two-inch PVC junction collar would be put on the front of the telescope. ? Here are a couple of photographs of one of the telescopes (mine). The entire telescope, including eyepieces and sunshield, is about 12 inches (30 cm) long. The students? telescopes are much better-looking than mine, since they used fast-drying plastic spray paint, indelible markers, and colored tape to make them beautiful. They also painted the inside of the tube black to reduce internal reflections. Not having remembered to ask their parents? permission to include, in Stardust, photos of them hard at work, I am unfortunately not submitting any such photos. ? ? ?????? Side view???????????????????????????????????????????? ???????? Front end view ? These telescopes have relatively short focal ratios (about f/4.2) and relatively wide fields of view. With the 12-mm eyepieces, they magnify things by about 18 times, and with the 20-mm eyepieces, it?s about 11x. ? The students had a great time putting the telescopes together. Following directions, and under adult supervision, they measured and sawed appropriate lengths of 1??? and 1? PVC tubing, wrapped masking tape around the latter, fitted all of the parts together, and then used PVC pipe cement to glue the appropriate parts together. I had previously used a metal lathe to square off the sections of 2-inch PVC pipe and to make a small ?lip? inside the front end, for the objective lens. (The lathe resides at the Chevy Chase Community Center?s woodshop, where I and Bill Blackmore conduct a telescope-making workshop every Friday evening.) Unfortunately, we discovered that there was quite a bit of variation in the interior diameter of the supposedly two-inch PVC pipe, so in some cases we had to use some more masking tape, and other methods, to make sure the lenses stayed in place. The PVC fittings were about $1.50 each at various local DC hardware stores, and we needed three of them per scope plus a few inches of PVC piping, so that added somewhere between $5 and $6 to the price of each telescope, for a grand total of about $13 or $14 each. ? At a subsequent Saturday session, the students took bars of aluminum that were about 50 mm by 10 mm by 3 mm, drilled holes in the center of the bars, and then tapped the holes with ?-20 tap and die bits so that they will fit on most standard tripods. They then put on, and tightened, a couple of hose clamps to fasten the aluminum bars to the longest section of their telescopes. Again, the hose clamps cost about $1.50 each, so the total now per scope is about $16 or $19 for what is, in essence, a very decent f/4.2 spotting scope with a nice wide, color-corrected field of view. ? As a final present to mark the end of the year?s session, the Carnegie Institution also gave each student a small, but serviceable, commercial tripod from Best Buy, so that the students could mount their telescopes on them, using the little mounting screw hole they had made, and so that they can easily keep a single object in view. (The tripods, which cost about $16 each, nearly doubled the price of the scopes!) ? As is apparently normal when one does this sort of thing, every single Saturday since we began the project, the weather has been either rainy or cloudy ? even when First Light took an overnight camping trip to the Eastern Shore of Maryland on April 24-25, specifically so that they could try out their telescopes! However, on that night, they did get to see the rings of Saturn through one of the telescopes that previous classes had made. This required dodging various holes in the cloud cover. A number of the children said that seeing Saturn was the most awesome thing that they had ever done. ? You may recall that Galileo?s telescopes were much simpler in design than today?s telescopes. (And I?m not referring to the PVC!) For one thing, the achromatic doublet, which bends the rays of light so that at least some of the colors seen by the eye aren?t all spread out, hadn?t been invented yet, so all of his images had annoying rainbows around the stars and planets. Plus, the glass that he used was of extremely poor quality by the standards of today, being filled with bubbles and striae, or places where the index of refraction of the glass changes right inside the lens. And, finally, instead of using convex lenses for his eyepieces, he instead used a bi-concave lens, which is supposed to provide an upright view, but gives an extremely narrow field of view. Inspired by a recent article in Sky and Telescope, we wanted to see this for ourselves. Here, we just used two pieces of PVC tubing, one sliding inside the other. To hold the lenses in place, I simply cut very short cylinders of PVC tube, about 5 mm long, in the shape of a ring. Then I cut away roughly 1/3 of the ring. Using considerable force, I was then able to bend the ring into a smaller shape that would fit inside the tube. Two of these rings, one in front of the lens, and one in back of the lens, held it quite firmly. ? Did Galileo have a narrow field of view? Oh, yes he did. I found the experience much like looking through a pea-shooter. One does indeed see things right-side up, but I begin to understand why some of Galileo?s contemporaries, when asked to look at celestial objects through his telescope, might perhaps have been telling the truth when they said that they couldn?t see anything. From stainless_steel at suddenlink.net Wed Jul 8 03:14:17 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 7 Jul 2009 13:14:17 -0500 Subject: [ATM] ATM: Joke In-Reply-To: <4A528F10.5050001@windstream.net> References: <2E8FA62B29464A6DB962A468879CCA71@R101> <4A528F10.5050001@windstream.net> Message-ID: <7CB943ADB9D941CC9BA68016422F2967@R101> Okay. I don't care what triggered his psychotic response. Her should find a good psychiatrist. D-LZ130 ----- Original Message ----- From: "waldo kitty" To: "ATM list" Sent: Monday, July 06, 2009 6:56 PM Subject: Re: [ATM] ATM: Joke > stainless_steel at suddenlink.net wrote: >> I made a joke, albeit a rather long one. No one got it. Does anyone have >> a sense of humor here? (No insult intended- did no one understand my >> joke about ballast/lightness?) > > personally? i got the joke about the ballast schtuffings but the overall > sidestream was... ummm... "over the top" which is what triggered the > "please > don't do that" response from another list member ;) > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.7/2222 - Release Date: 07/07/09 05:53:00 From stainless_steel at suddenlink.net Wed Jul 8 03:29:06 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 7 Jul 2009 13:29:06 -0500 Subject: [ATM] Fw: ATM Wide ranging interests: Message-ID: ----- Original Message ----- From: "Richard Schwartz" To: Sent: Tuesday, July 07, 2009 7:36 AM Subject: RE: [ATM] ATM Wide ranging interests: How do you get the governor to consent to a tube in his ass? -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of stainless_steel at suddenlink.net Sent: Monday, July 06, 2009 3:34 PM To: lenses at roadrunner.com; ATM list Subject: Re: [ATM] ATM Wide ranging interests: Baerings, axles, machining, woodwork- the list could go on and on. http://www.atmsite.org/contrib/Harbour/index.html Thanks, Dave. Dave (P.S. I have even devised a drive that uses wind power; regulation of rpm is the secret.) ----- Original Message ----- From: To: "ATM list" Sent: Monday, July 06, 2009 5:21 PM Subject: Re: [ATM] ATM Wide ranging interests: > Sure am interested in "everything" > Sometimes I break glass > :) > > ---- David Weinshenker wrote: >> stainless_steel at suddenlink.net wrote: >> > If none of you are interested in wider ranger interests, which ATM >> > is >> > about >> >> Of course we are! There's more to telescope-making >> than "pushing glass"! >> >> -dave w >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ ---------------------------------------------------------------------------- ---- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.5/2220 - Release Date: 07/05/09 17:54:00 _______________________________________________ ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.7/2222 - Release Date: 07/07/09 05:53:00 From rmay at nethere.com Wed Jul 8 04:55:22 2009 From: rmay at nethere.com (Bob May) Date: Tue, 7 Jul 2009 12:55:22 -0700 Subject: [ATM] refractor clarification References: <338084.41947.qm@web35803.mail.mud.yahoo.com><7b48d05a0907050337o16747e74madcc81e6c1ad00f2@mail.gmail.com> <7b48d05a0907070401s494d2fb8ka890d905a9d33078@mail.gmail.com> Message-ID: <001101c9ff3c$ddc0f1e0$51ff1345@amd> Generally, when a pair of lenses are sold as a unit, they are, to some degree or another at least achromatic in their perrformance. The field of designing lenses is a huge complex one to get the best performance out of a few pieces of glass. Not only are the curves and thickness of the lenses important but you also gain correction by the spacing between the two lenses. If you want to get into more optical workings, there is a series of courses (they're college level but that doesn't mean that they're difficult) By a Dr. J.C. Whyantt at the U of Ariz. Sorry, but I don't have the URL at hand. He's got stuff on testing as well. You might also want to check out what the U, of Rochester has as that is another place that teaches optics. For your own studies, there are several books on lens design. Smith, Conrady, Kingslake and so forth are all, in their way, decently good college level books on optical theory. Then there is the Rutten and VanRooij book sold by Willmann-Bell ($25 for the book and another for the software) which does basic theory and design stuff for telescope optics of all kinds. Of course, you don't have to know all of this for using a telescope but for making your own, especially if you want to dabble in refractors, will help a lot. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From mikell at optonline.net Wed Jul 8 09:25:44 2009 From: mikell at optonline.net (Michael Lindner) Date: Tue, 07 Jul 2009 20:25:44 -0400 Subject: [ATM] Fw: ATM Wide ranging interests: Re: ATM: Joke In-Reply-To: References: Message-ID: <4A53E788.6060801@optonline.net> These threads are seriously deteriorating the signal/noise ratio of this list. Yes, we all have interests, but this isn't the appropriate place for all of them. If you want to have side discussions with your friends, there's facebook. Let's try to keep this list for ATM-related topics. -- Michael Lindner http://www.starastronomy.org *** http://home.att.net/~mikel http://www.atmsite.org *** http://www.atmlist.net From rgafron at sbcglobal.net Wed Jul 8 09:38:20 2009 From: rgafron at sbcglobal.net (Ron Gafron) Date: Tue, 07 Jul 2009 19:38:20 -0500 Subject: [ATM] Fw: ATM Wide ranging interests: Re: ATM: Joke In-Reply-To: <4A53E788.6060801@optonline.net> References: <4A53E788.6060801@optonline.net> Message-ID: <4A53EA7C.7030709@sbcglobal.net> As a long time lurker here (and one-time ATM-er before my kids decided my time was better spent elsewhere), I'm pretty comfortable saying that of the vast majority of messages that come to me from the ATM list, very, very few are off-topic, and, honestly, not even close to "seriously deteriorating the signal/noise ratio of this list". Every once in awhile, a thread will go where it probably shouldn't, but those are few and far between. They seem to increase for a few days, and then fade away just as quickly. I would think that the ATM community on this list can handle that with little gnashing of teeth. The easy solution is to just not read those messages that don't interest someone; the "delete" key works quickly and painlessly. Michael Lindner wrote: > These threads are seriously deteriorating the signal/noise ratio of > this list. Yes, we all have interests, but this isn't the appropriate > place for all of them. > > If you want to have side discussions with your friends, there's > facebook. Let's try to keep this list for ATM-related topics. > From vorblesnak at peak.org Wed Jul 8 12:33:11 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Tue, 7 Jul 2009 20:33:11 -0700 (PDT) Subject: [ATM] Bob's glass and foam blank .. a fix Message-ID: <4860.69.59.200.230.1247023991.squirrel@webmail.peak.org> Bob had emailed that the blank had tension problems, probably from the adhesive. I was going to try a fix I suggested, fill in the voids, but first I did a star test and then I stopped to look at the surface. The lines were pretty bad, almost a kind of astigmatism, but not quite. Then I dropped the tester a few inches and looked at the surface of the glass at ROC. There were two dark zones on the surface in the 50% to 70% area. These are the same type of dark zones I have been chasing out of the tessellated blank. They are deep zones and they do not polish out. I have had to fine grind three times to chase them out of the tessellated blank. I suspect they are due to pressure during coarse grinding, though they could be tension in the glass that relieved after grinding. What I have found that works is to drop back to 500 grit and use a very light tool. No more than a pound or two. For Bob's blank I used a 1/2 pint canning jar. I do a long wet and then a flash polish. If I still have dark zones I do another wet of 500. What I am doing is flattening the surface, making it all the same. Then I polish with a light weight lap, no more than 3 or 4 pounds, maybe five on a big mirror. It means I have to polish longer but the figure does not suffer. Even with the glass foam backing I have to treat it as thin glass. Bottom line, I have fixed the blank. It needs to be polished out but the figure is workable and the strange twist is gone. I will take a picture when I get a chance. How are the other glass and foam blanks coming along? David Davis Toledo, OR 97391 From blaktony86 at yahoo.com Thu Jul 9 00:52:16 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Wed, 8 Jul 2009 08:52:16 -0700 (PDT) Subject: [ATM] alcoat.net is good service! Message-ID: <702001.80703.qm@web81903.mail.mud.yahoo.com> I just want to let the atm guys know that alcoat.net is an excellent aluminizing service for ATMers. Service was extremley fast. I received my mirror in 8 days and thats with shipping both ways! Coating looks great and everything packaged well. The price is also a lot better than other commerical manufacturers. I recommend this place to every ATM. -Tony From stainless_steel at suddenlink.net Thu Jul 9 01:28:00 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 8 Jul 2009 11:28:00 -0500 Subject: [ATM] Fw: ATM Wide ranging interests: Re: ATM: Joke In-Reply-To: <4A53E788.6060801@optonline.net> References: <4A53E788.6060801@optonline.net> Message-ID: Okay! Roger, Wilco. D-LZ130 ----- Original Message ----- From: "Michael Lindner" Cc: "ATM list" Sent: Tuesday, July 07, 2009 7:25 PM Subject: Re: [ATM] Fw: ATM Wide ranging interests: Re: ATM: Joke > These threads are seriously deteriorating the signal/noise ratio of this > list. Yes, we all have interests, but this isn't the appropriate place > for all of them. > > If you want to have side discussions with your friends, there's > facebook. Let's try to keep this list for ATM-related topics. > > -- > Michael Lindner > http://www.starastronomy.org *** http://home.att.net/~mikel > http://www.atmsite.org *** http://www.atmlist.net > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.8/2224 - Release Date: 07/08/09 05:53:00 From stainless_steel at suddenlink.net Thu Jul 9 01:53:35 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 8 Jul 2009 11:53:35 -0500 Subject: [ATM] ATM: I have nice photo of the templates for the destroyed mounting. Please ask for them in an html email Message-ID: <198998F707CB4D5BB0DA15DEDF7B2399@R101> All: I have a nice, single example of the kind of templates I had available for those who wanted to come to Enid and save about a thousand hours of layout time, to precision tolerances. Ask for them, and I will send them to you. I also have an entire, complete catalogue for this mounting. It is yours for the asking. The mounting is gone, completely DESTROYED. D-LZ130 From rflrs at verizon.net Thu Jul 9 08:59:08 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Wed, 08 Jul 2009 19:59:08 -0400 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <002e01c9fec1$25eb7160$3dff1345@amd> References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu> <002e01c9fec1$25eb7160$3dff1345@amd> Message-ID: <4A5532CC.2080002@verizon.net> Bob May wrote: > I don't have any more glasses floating about, they have all been > turned into small telescopes. My next door neighbor doesn't > understand why I feel the need for large diameter glasses and > when I tell her I've got aperture fever, she has no idea of what > I'm saying. When one is down to those "too thin" pieces of glass (if that's the case), and doesn't want to cut them down to a smaller diameter, maybe a different tack would do: Title: trp02-45x 150 mm f/12 Triplet First surface figuring: -8.9631619e-12*r^4 + 1.7639013e-16*r^6 Surf Radius Thickness Glass Diameter STO 1086 12 N-BK7 156 2 Infinity 12 N-BAK1 156 3 -600 6.9 N-F2 156 4 -3878 1783.156 156 IMA -674.934 42.2 Each glass is thinner than (or equal to) 12 mm. Extra glass, though, was added to the BK-7, both to match the other two and to allow for figuring with a stiffer blank. The figuring itself here is only about 0.05 micron or so from a sphere. Without it, the green line is still better than lambda/17 P-V or lambda/60 RMS, so one might actually consider not figuring at all, provided the glass doesn't vary too much. With it, though, the green line is "aplanatic" with extra correction to reduce zonal errors. From stainless_steel at suddenlink.net Thu Jul 9 09:21:02 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 8 Jul 2009 19:21:02 -0500 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <4A5532CC.2080002@verizon.net> References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu><002e01c9fec1$25eb7160$3dff1345@amd> <4A5532CC.2080002@verizon.net> Message-ID: <0E5E443E232F4091AC7F900BB0082B0C@R101> /Thanks, Bob /onlyofd \\\ \\sccest;I disabled K\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\good su,ggestio ----- Original Message ----- From: "Richard F.L.R. Snashall" To: "ATM List" Sent: Wednesday, July 08, 2009 6:59 PM Subject: Re: [ATM] ATM Wide ranging interests: > Bob May wrote: >> I don't have any more glasses floating about, they have all been >> turned into small telescopes. My next door neighbor doesn't >> understand why I feel the need for large diameter glasses and >> when I tell her I've got aperture fever, she has no idea of what >> I'm saying. > When one is down to those "too thin" pieces of glass (if that's > the case), and doesn't want to cut them down to a smaller > diameter, maybe a different tack would do: > > Title: trp02-45x > 150 mm f/12 Triplet > First surface figuring: -8.9631619e-12*r^4 + 1.7639013e-16*r^6 > > Surf Radius Thickness Glass Diameter > > STO 1086 12 N-BK7 156 > 2 Infinity 12 N-BAK1 156 > 3 -600 6.9 N-F2 156 > 4 -3878 1783.156 156 > IMA -674.934 42.2 > > Each glass is thinner than (or equal to) 12 mm. Extra glass, > though, was added to the BK-7, both to match the other two > and to allow for figuring with a stiffer blank. > > The figuring itself here is only about 0.05 micron or so from > a sphere. Without it, the green line is still better than > lambda/17 P-V or lambda/60 RMS, so one might actually consider > not figuring at all, provided the glass doesn't vary too much. > With it, though, the green line is "aplanatic" with extra > correction to reduce zonal errors. > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.8/2224 - Release Date: 07/08/09 05:53:00 From pauldkline at aol.com Thu Jul 9 22:19:12 2009 From: pauldkline at aol.com (pauldkline at aol.com) Date: Thu, 09 Jul 2009 09:19:12 -0400 Subject: [ATM] Out of big glass - Make a miniature Message-ID: <8CBCEAEFBD04357-EFC-5D3@webmail-mh31.sysops.aol.com> Mr. May says his remaining glass is too small, why not make a miniature lens?? Alvaro Amaro de Azevedo wrote a series of articles?for microscopy-uk.org on the manufacture and setting of sub-millimeter lenses for microscopy.? He even ground some using beach sand that he ball-milled and levigated, though his most recent technique involves diamond grit and paste.? He succeded in making doublets, perhaps some application for eyepieces - or camera lenses? http://www.microscopy-uk.org.uk/mag/artjan06/aalens2.html http://www.sas.org/tcs/weeklyIssues_2006/2006-01-13/project1/ http://www.microscopy-uk.org.uk/mag/artjul06/aa-lens3.html http://www.microscopy-uk.org.uk/mag/artdec06/aa-pocket-micro.pdf http://www.microscopy-uk.org.uk/mag/imgjun07/aa-lensnew.pdf There's also Roger Baker's article on the making of miniature doublets using glycerine droplets: http://www.science-info.org/pages/Roger%20Baker/homemade-microscope.pdf We?can't get glycerine anymore at the drugstores around here, I suppose it is a Homeland Security issue, but Hobby Lobby has it. Paul K From rflrs at verizon.net Thu Jul 9 22:53:33 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Thu, 09 Jul 2009 09:53:33 -0400 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <4A5532CC.2080002@verizon.net> References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu> <002e01c9fec1$25eb7160$3dff1345@amd> <4A5532CC.2080002@verizon.net> Message-ID: <4A55F65D.5010006@verizon.net> Richard F.L.R. Snashall wrote: > When one is down to those "too thin" pieces of glass (if that's > the case), and doesn't want to cut them down to a smaller > diameter, maybe a different tack would do: > > Title: trp02-45x > 150 mm f/12 Triplet > First surface figuring: -8.9631619e-12*r^4 + 1.7639013e-16*r^6 > > Surf Radius Thickness Glass Diameter > > STO 1086 12 N-BK7 156 > 2 Infinity 12 N-BAK1 156 > 3 -600 6.9 N-F2 156 > 4 -3878 1783.156 156 > IMA -674.934 42.2 Or, with each having 11 mm or less thickness (as it depends on exactly what glass is left over): Title: trp02-48x 150 mm f/12 Triplet First surface figuring: -7.3939024e-12*r^4 + 1.3270447e-16*r^6 Surf Radius Thickness Glass Diameter STO 1090 11 N-BK7 156 2 Infinity 11 N-BAK4 156 3 -752 6.9 N-SF5 156 4 -3051 1784.946 156 IMA -670.305 42.5 From rmay at nethere.com Fri Jul 10 04:57:30 2009 From: rmay at nethere.com (Bob May) Date: Thu, 9 Jul 2009 12:57:30 -0700 Subject: [ATM] ATM Wide ranging interests: References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu><002e01c9fec1$25eb7160$3dff1345@amd> <4A5532CC.2080002@verizon.net> Message-ID: <000201ca00cf$7eaa4a00$dcff1345@amd> Yeah, but who makes those glasses and which style? I will say that going down to Bloomie's for a set of 4 glasses for some horrible price really isn't gonna happen. I will note that I found some large size tumblers at the 99 cent store that aren't too bad dor size. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From stainless_steel at suddenlink.net Fri Jul 10 05:14:39 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 9 Jul 2009 15:14:39 -0500 Subject: [ATM] Out of big glass - Make a miniature In-Reply-To: <8CBCEAEFBD04357-EFC-5D3@webmail-mh31.sysops.aol.com> References: <8CBCEAEFBD04357-EFC-5D3@webmail-mh31.sysops.aol.com> Message-ID: <36E6EC3357494579931108F4602E11C2@R101> Bob shoulld try making some ultra high powered eyepieces, single element, ball shaped. They worked for the Herschels for magnifications (which they needed, for double star work) of up to 6,000X. I had a copy of a short lived magazine, even corresponded with the owner- I forget the name of the magazine- it was about how to do science fair projects. It went belly up, but he gave a detauiled acount of how to grind and polish these tiny beads,. and how to mount them Leowohook style, for microscopes in the style of this pioneeer. He said with these tiny ball lenses he could just barely see protozoa. With a singhle element lens! Her must have been pretty brave to get his eye that close to the glass. If it touched my cornea, I would be upset. D-LZ130 ----- Original Message ----- From: To: Sent: Thursday, July 09, 2009 8:19 AM Subject: [ATM] Out of big glass - Make a miniature > Mr. May says his remaining glass is too small, why not make a miniature > lens?? > > Alvaro Amaro de Azevedo wrote a series of articles?for microscopy-uk.org > on the manufacture and setting of sub-millimeter lenses for microscopy.? > He even ground some using beach sand that he ball-milled and levigated, > though his most recent technique involves diamond grit and paste.? He > succeded in making doublets, perhaps some application for eyepieces - or > camera lenses? > > http://www.microscopy-uk.org.uk/mag/artjan06/aalens2.html > http://www.sas.org/tcs/weeklyIssues_2006/2006-01-13/project1/ > http://www.microscopy-uk.org.uk/mag/artjul06/aa-lens3.html > http://www.microscopy-uk.org.uk/mag/artdec06/aa-pocket-micro.pdf > http://www.microscopy-uk.org.uk/mag/imgjun07/aa-lensnew.pdf > > There's also Roger Baker's article on the making of miniature doublets > using glycerine droplets: > > http://www.science-info.org/pages/Roger%20Baker/homemade-microscope.pdf > > We?can't get glycerine anymore at the drugstores around here, I suppose it > is a Homeland Security issue, but Hobby Lobby has it. > > Paul K > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.8/2227 - Release Date: 07/09/09 05:55:00 From rflrs at verizon.net Fri Jul 10 06:14:28 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Thu, 09 Jul 2009 17:14:28 -0400 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <000201ca00cf$7eaa4a00$dcff1345@amd> References: <367D452938AA4580A65B7848C44B4BB2@R101> <4A528734.2050004@psu.edu><002e01c9fec1$25eb7160$3dff1345@amd> <4A5532CC.2080002@verizon.net> <000201ca00cf$7eaa4a00$dcff1345@amd> Message-ID: <4A565DB4.50505@verizon.net> Bob May wrote: > Yeah, but who makes those glasses and which style? I will say > that going down to Bloomie's for a set of 4 glasses for some > horrible price really isn't gonna happen. > I will note that I found some large size tumblers at the 99 cent > store that aren't too bad dor size. The intent was to use some of the common Schott glasses. No, they are not from Bloomie's or even Wall-Emart;-). You can, for the most part, though, substitute the non-ECO version of the glass for the ECO versions. Mostly, it just causes a small shift in the focus, but will modify the figuring a bit, too. Even less in this instance: Title: trp02-51x 150 mm f/12 Triplet First surface figuring: -1.3642042e-12*r^4 + 1.7179253e-16*r^6 Surf Radius Thickness Glass Diameter STO 1094.5 11.5 N-BK7 156 2 Infinity 11.5 N-BAK4 156 3 -675 6.9 SF2 156 -- no Schott ECO 4 -3221 1784.531 156 IMA -672.01 42.2 Note the figuring here is less than a tenth of that of the others -- less than 5 nanometers. From stainless_steel at suddenlink.net Fri Jul 10 06:47:56 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 9 Jul 2009 16:47:56 -0500 Subject: [ATM] ATM Wide ranging interests: In-Reply-To: <4A565DB4.50505@verizon.net> References: <367D452938AA4580A65B7848C44B4BB2@R101><4A528734.2050004@psu.edu><002e01c9fec1$25eb7160$3dff1345@amd><4A5532CC.2080002@verizon.net> <000201ca00cf$7eaa4a00$dcff1345@amd> <4A565DB4.50505@verizon.net> Message-ID: <347A33019E504B628307A26962A96D67@R101> Will you kindly change the subject line, since it belongs to me? Thank you. It bears no interested to what I was trying to say. D-LZ130 ----- Original Message ----- From: "Richard F.L.R. Snashall" To: Sent: Thursday, July 09, 2009 4:14 PM Subject: Re: [ATM] ATM Wide ranging interests: > Bob May wrote: >> Yeah, but who makes those glasses and which style? I will say >> that going down to Bloomie's for a set of 4 glasses for some >> horrible price really isn't gonna happen. >> I will note that I found some large size tumblers at the 99 cent >> store that aren't too bad dor size. > > The intent was to use some of the common Schott glasses. No, > they are not from Bloomie's or even Wall-Emart;-). You can, > for the most part, though, substitute the non-ECO version of > the glass for the ECO versions. Mostly, it just causes a > small shift in the focus, but will modify the figuring a bit, > too. > > Even less in this instance: > > Title: trp02-51x > 150 mm f/12 Triplet > First surface figuring: -1.3642042e-12*r^4 + 1.7179253e-16*r^6 > > Surf Radius Thickness Glass Diameter > > STO 1094.5 11.5 N-BK7 156 > 2 Infinity 11.5 N-BAK4 156 > 3 -675 6.9 SF2 156 -- no Schott ECO > 4 -3221 1784.531 156 > IMA -672.01 42.2 > > Note the figuring here is less than a tenth of that of the > others -- less than 5 nanometers. > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.8/2227 - Release Date: 07/09/09 05:55:00 From gfbrandenburg at yahoo.com Fri Jul 10 07:15:13 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Thu, 9 Jul 2009 15:15:13 -0700 (PDT) Subject: [ATM] glass (was Re: ATM Wide ranging interests:) Message-ID: <406432.72026.qm@web111514.mail.gq1.yahoo.com> Is it OK to use shot glasses and bottoms of white wine or whiskey bottles instead of true Schott glass? Or will that cause too much astigmatism, coma, and general blurry eyes? Sorry. I will stop now. Guy Brandenburg, Washington, DC --- On Thu, 7/9/09, Richard F.L.R. Snashall wrote: > From: Richard F.L.R. Snashall > Subject: Re: [ATM] ATM Wide ranging interests: > To: atm at atmlist.net > Date: Thursday, July 9, 2009, 5:14 PM > Bob May wrote: > > Yeah, but who makes those glasses and which > style?? I will say > > that going down to Bloomie's for a set of 4 glasses > for some > > horrible price really isn't gonna happen. > > I will note that I found some large size tumblers at > the 99 cent > > store that aren't too bad dor size. > > The intent was to use some of the common Schott > glasses.? No, > they are not from Bloomie's or even Wall-Emart;-).? > You can, > for the most part, though, substitute the non-ECO version > of > the glass for the ECO versions.? Mostly, it just > causes a > small shift in the focus, but will modify the figuring a > bit, > too. > > Even less in this instance: > > Title: trp02-51x > 150 mm f/12 Triplet > First surface figuring: -1.3642042e-12*r^4 + > 1.7179253e-16*r^6 > > Surf? ???Radius? Thickness? > ? Glass? Diameter > > STO? ???1094.5? ? > ???11.5? ? N-BK7? ? > ???156 > ? 2???Infinity? ? > ???11.5???N-BAK4? ? > ???156 > ? 3? ? ???-675? ? > ? ? 6.9? ? ? SF2? ? > ???156? -- no Schott ECO > ? 4? ? ? > -3221???1784.531? ? ? ? > ? ? ? ? 156 > IMA? ? -672.01? ? ? ? ? > ? ? ? ? ? ? ? ? > 42.2 > > Note the figuring here is less than a tenth of that of the > others -- less than 5 nanometers. > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From atmpob at yahoo.com Fri Jul 10 10:11:22 2009 From: atmpob at yahoo.com (Dale Eason) Date: Thu, 9 Jul 2009 18:11:22 -0700 (PDT) Subject: [ATM] glass (was Re: ATM Wide ranging interests:) Message-ID: <883904.44465.qm@web54504.mail.re2.yahoo.com> As we are usually reminded on this list it depends on how well annealed you are. You need to look at your reflection through two polorizers. Adjust them until you can no longer see a glow around your nose. If the rest of you is still glowing then you have too much Schott glass. Dale Eason --- On Thu, 7/9/09, Guy Brandenburg wrote: > From: Guy Brandenburg > Subject: [ATM] glass (was Re: ATM Wide ranging interests:) > To: atm at atmlist.net, "Richard F.L.R. Snashall" > Date: Thursday, July 9, 2009, 5:15 PM > > Is it OK to use shot glasses and bottoms of white wine or > whiskey bottles instead of true Schott glass? Or will that > cause too much astigmatism, coma, and general blurry eyes? > > Sorry. I will stop now. > From holmmarkd at gmail.com Fri Jul 10 11:14:26 2009 From: holmmarkd at gmail.com (Mark Holm) Date: Thu, 09 Jul 2009 22:14:26 -0400 Subject: [ATM] Low Pressure Sodium Ballast In-Reply-To: References: Message-ID: <4A56A402.1020809@gmail.com> Atlanta Light Bulbs, Inc. sells low pressure sodium ballasts. Not so cheap though. http://www.atlantalightbulbs.com/ecart/10Browse.asp?Category=B-HID+LPS+0-180W Low pressure sodium lamps take a while to heat up. It is several minutes from switch on to full output. The green lines in fluorescent tubes come from the mercury arc discharge. There are several other narrow lines in the mercury spectrum, but the green is brightest, not the least because human eyes are most sensitive there. Mercury discharge makes a lot of UV. That is why some can be used as germicidal lamps. If you use a germicidal lamp, make sure to go overboard on the UV filtering, because the tube hasn't any and is pumping out a whole lot of UV, enough to kill things. You don't want it killing your retina. Actually, I would go overboard on UV filtering any uncoated mercury tube, just to be safe. I like to see. Most people think the low pressure mercury discharge is way too green for use as a general purpose illuminant, and also the energy in the UV goes to waste. Hence the phosphor coating in ordinary fluorescent tubes. The phosphor absorbs UV and emits in various bands, depending on the type of phosphor. The bands are still narrow compared to sunlight, but much wider than the narrow lines from the mercury discharge. Fortunately, manufacturers do not use green emitting phosphors. The mercury green lines already pump out more than enough green. So, if you filter green, with rather wide band, inexpensive filters, you can reasonably isolate the green lines, because the manufacturers use phosphors that make red, yellow and blue to fill out the spectrum, but not green and because the nearest strong lines in the mercury spectrum are sufficiently far away. I say green lines because there is a doublet, but for our sort of interferometry they are close enough together to often be used as if there were only one line. -- Mark Holm markholm at verizon.net holmmarkd at gmail.com From rflrs at verizon.net Fri Jul 10 15:53:31 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Fri, 10 Jul 2009 02:53:31 -0400 Subject: [ATM] glass selection In-Reply-To: <883904.44465.qm@web54504.mail.re2.yahoo.com> References: <883904.44465.qm@web54504.mail.re2.yahoo.com> Message-ID: <4A56E56B.2070805@verizon.net> Dale Eason wrote: > As we are usually reminded on this list it depends on how well annealed you are. You need to look at your reflection through two polorizers. Adjust them until you can no longer see a glow around your nose. If the rest of you is still glowing then you have too much Schott glass. > > Dale Eason > > --- On Thu, 7/9/09, Guy Brandenburg wrote: > >> From: Guy Brandenburg >> Subject: [ATM] glass (was Re: ATM Wide ranging interests:) >> To: atm at atmlist.net, "Richard F.L.R. Snashall" >> Date: Thursday, July 9, 2009, 5:15 PM >> >> Is it OK to use shot glasses and bottoms of white wine or >> whiskey bottles instead of true Schott glass? Or will that >> cause too much astigmatism, coma, and general blurry eyes? >> >> Sorry. I will stop now. I should remember that it's too close to Stellafane. People's heads are in the clouds and hearts are at a swapmeet! But just for that: Title: trp02-53x 150 mm f/12 Triplet First surface figuring: -2.484e-12*r^4 + 1.342e-16*r^6 (c. 1/100 micron) Surf Radius Thickness Glass Diameter STO 1089 10.5 OPTIWHITE 156 2 Infinity 10.5 PYREX 156 3 -883 7 SF10 156 4 -1979 1785.964 156 IMA -661.53 42.2 For Optiwhite, just substitute window or counter top; the Pyrex, of course, gets ripped out of that Dob; that Lead Crystal 25 year award they gave you can substitute for SF10. ;-) From anishmangal2002 at gmail.com Fri Jul 10 16:12:43 2009 From: anishmangal2002 at gmail.com (Anish Mangal) Date: Fri, 10 Jul 2009 12:42:43 +0530 Subject: [ATM] Invitation to view webalbum Message-ID: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> Hi all, I had sent an invitation mail to the list to view my webalbum of some of the astrophotos I've taken. Don't think it got through to the list because of the images and html embedded in it. Sending a text form of it. """ Here are some pics I took using the 8" dob I recently completed. The camera used in afocal images is Sony DSC W70. I used a logitech "quickcam family" webcam and modified it for the prime-focus photographs. These images, and the telescope itself is a result of the invaluable guidance provided by the members of this atmlist. http://picasaweb.google.com/lh/sredir?uname=anishmangal2002&target=ALBUM&id=5352\064327601862257&authkey=Gv1sRgCMXto4Cy0ve4Rw&invite=CNTN7PgP&feat=email """ Clear Skies, Anish Mangal From john_lynch2007 at yahoo.com Fri Jul 10 20:54:28 2009 From: john_lynch2007 at yahoo.com (John Lynch) Date: Fri, 10 Jul 2009 04:54:28 -0700 (PDT) Subject: [ATM] Baader 9X60mm finder telescope Message-ID: <409730.92445.qm@web110111.mail.gq1.yahoo.com> To the group: ? Has anyone had the opportunity to use the Baader 9X60mm finder telescope?? Any information would be appreciated.? The only references that I'm able to find are on the Baader Planetarium website and Alpine Astro (US dealer), but neither gives very much detail. ? BTW, I was recently informed that the Baader Star Spectroscope is being redesigned and anticipated to be re-introduced late this year.? FYI, some of the websites that carry Baader products?currently indicate "Discontinued" or "Not currently available." ? Regards, ? John Lynch From mjc5 at psu.edu Fri Jul 10 21:01:23 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Fri, 10 Jul 2009 08:01:23 -0400 Subject: [ATM] Out of big glass - Make a miniature In-Reply-To: <36E6EC3357494579931108F4602E11C2@R101> References: <8CBCEAEFBD04357-EFC-5D3@webmail-mh31.sysops.aol.com> <36E6EC3357494579931108F4602E11C2@R101> Message-ID: <33D8676D-9F05-4553-9EC9-CF484DFBE429@psu.edu> On Jul 9, 2009, at 4:14 PM, wrote: > Bob shoulld try making some ultra high powered eyepieces, single > element, ball shaped. They worked for the Herschels for > magnifications (which they needed, for double star work) of up to > 6,000X. There was a fellow here - I think it was Tom Krajci several years ago, who used a ball ep on occasion. IIRC, the verdict was it had a very small sweet spot, but what a sweet spot! -73 de Mike N3LI - From ericandroberta at sbcglobal.net Sat Jul 11 00:37:48 2009 From: ericandroberta at sbcglobal.net (D ERIC ALLEN) Date: Fri, 10 Jul 2009 08:37:48 -0700 (PDT) Subject: [ATM] 24" mirror finished Message-ID: <635098.76284.qm@web80504.mail.mud.yahoo.com> For those aware of my long-running (nine years) mirror project, I have finally finished the 24" f/4 primary for my Nasmyth-style cassegrain.? The secondary is as yet unstarted.? I just turned 64 today, so lets hope it doesn't take nine years for the secondary.? R of C is 191.75".? Strehl is .994 (readings on two diameters averaged), but the individual diameters don't look that good, and as I say, I still have the secondary to do.? Anyway, I'm glad it's finished. Eric From stainless_steel at suddenlink.net Sat Jul 11 01:31:42 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Fri, 10 Jul 2009 11:31:42 -0500 Subject: [ATM] Invitation to view webalbum In-Reply-To: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> References: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> Message-ID: <33672FD9B7AA4311A5B55CD1586C75D8@R101> Anish, Thank you for the asrtophotos. You are ready for a camera that does not employ "afocal" focusing (that you can remove the lens from). That is the Canon. You will perform brilliantly with this camera. DLZ-130 ----- Original Message ----- From: "Anish Mangal" To: "ATM list" Sent: Friday, July 10, 2009 2:12 AM Subject: [ATM] Invitation to view webalbum > Hi all, > > I had sent an invitation mail to the list to view my webalbum of some of > the > astrophotos I've taken. Don't think it got through to the list because of > the images and html embedded in it. Sending a text form of it. > > """ > Here are some pics I took using the 8" dob I recently completed. The > camera > used in afocal images is Sony DSC W70. I used a logitech "quickcam family" > webcam and modified it for the prime-focus photographs. These images, and > the > telescope itself is a result of the invaluable guidance provided by the > members of this > atmlist. > > http://picasaweb.google.com/lh/sredir?uname=anishmangal2002&target=ALBUM&id=5352\064327601862257&authkey=Gv1sRgCMXto4Cy0ve4Rw&invite=CNTN7PgP&feat=email > """ > > Clear Skies, > Anish Mangal > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.9/2229 - Release Date: 07/10/09 07:05:00 From wkitty42 at windstream.net Sat Jul 11 04:09:21 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Fri, 10 Jul 2009 15:09:21 -0400 Subject: [ATM] Invitation to view webalbum In-Reply-To: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> References: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> Message-ID: <4A5791E1.4050308@windstream.net> Anish Mangal wrote: > """ > Here are some pics I took using the 8" dob I recently completed. The camera > used in afocal images is Sony DSC W70. I used a logitech "quickcam family" > webcam and modified it for the prime-focus photographs. These images, and > the > telescope itself is a result of the invaluable guidance provided by the > members of this > atmlist. > > http://picasaweb.google.com/lh/sredir?uname=anishmangal2002&target=ALBUM&id=5352\064327601862257&authkey=Gv1sRgCMXto4Cy0ve4Rw&invite=CNTN7PgP&feat=email > """ picasaweb says that account doesn't have any public albums available in it... check your settings for that album to ensure that everyone can view ;) From vorblesnak at peak.org Sat Jul 11 04:08:58 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Fri, 10 Jul 2009 12:08:58 -0700 (PDT) Subject: [ATM] Soft focus Message-ID: <39983.4.242.237.186.1247252938.squirrel@webmail.peak.org> I did a bit of star testing with the tessellated blank last night. I was able to split Mizar / Alcor in the handle of the dipper so I have some definition, but all of the stars are small fuzzy blobs. Why? Could be the tessellations are not all coming to focus in the same place and so softening the final image. Could be poor figure. Could be ... ??? What? That is what I am looking for. What can cause a soft focus? My gut feeling is it is caused by a lack of coherency. But throw me some ideas. Thinking it might be an edge issue I stopped the mirror down to a 12 inch and then 6 inch, hide the edge, less aperture, longer focal ratio. Still just fuzzy little blobs. David Davis Toledo, OR 97391 From broward32666 at yahoo.com Sat Jul 11 04:18:42 2009 From: broward32666 at yahoo.com (Charles Broward) Date: Fri, 10 Jul 2009 12:18:42 -0700 (PDT) Subject: [ATM] Invitation to view webalbum In-Reply-To: <4A5791E1.4050308@windstream.net> References: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> <4A5791E1.4050308@windstream.net> Message-ID: <404750.86587.qm@web110802.mail.gq1.yahoo.com> Hi, Re Anish's link....I had to copy all three lines and paste it into my browser...then it went to the album. Clear sky (which has been non-existant in n. Florida C.S.Broward GhastlySky Observatory Gainesville, Florida Anish Mangal wrote: > """ > Here are some pics I took using the 8" dob I recently completed. The camera > used in afocal images is Sony DSC W70. I used a logitech "quickcam family" > webcam and modified it for the prime-focus photographs. These images, and > the > telescope itself is a result of the invaluable guidance provided by the > members of this > atmlist. > > http://picasaweb.google.com/lh/sredir?uname=anishmangal2002&target=ALBUM&id=5352\064327601862257&authkey=Gv1sRgCMXto4Cy0ve4Rw&invite=CNTN7PgP&feat=email > """ picasaweb says that account doesn't have any public albums available in it... check your settings for that album to ensure that everyone can view ;) _______________________________________________ ATM mailing list http://www.atmlist.net/ From rmay at nethere.com Sat Jul 11 06:10:51 2009 From: rmay at nethere.com (Bob May) Date: Fri, 10 Jul 2009 14:10:51 -0700 Subject: [ATM] glass selection References: <883904.44465.qm@web54504.mail.re2.yahoo.com> <4A56E56B.2070805@verizon.net> Message-ID: <001001ca01a2$e8381640$82ff1345@amd> Richard, more try a Wallymart ordinary 16oz. glass and a large leaded crystal schotch glass. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Sat Jul 11 06:16:38 2009 From: rmay at nethere.com (Bob May) Date: Fri, 10 Jul 2009 14:16:38 -0700 Subject: [ATM] 24" mirror finished References: <635098.76284.qm@web80504.mail.mud.yahoo.com> Message-ID: <001f01ca01a3$b72913a0$82ff1345@amd> The secondary is going to be calling for some star work. Get it roughed out to approximtely the right ROC and put some kind of shape on it. Having a test plate with the correct shape on it will help in making the proper shape for the secondary and star testing will finish it up nicely. It will help if the primary has a nice smooth shape according to a Ronch Grating. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From wkitty42 at windstream.net Sat Jul 11 06:31:01 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Fri, 10 Jul 2009 17:31:01 -0400 Subject: [ATM] Invitation to view webalbum In-Reply-To: <404750.86587.qm@web110802.mail.gq1.yahoo.com> References: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> <4A5791E1.4050308@windstream.net> <404750.86587.qm@web110802.mail.gq1.yahoo.com> Message-ID: <4A57B315.80803@windstream.net> Charles Broward wrote: > Hi, Re Anish's link....I had to copy all three lines and paste it into my browser...then it went to the album. three lines? the latest thunderbird shows me one really long line... when i click on it, the latest firefox opens and jumps thru a redirector (the "redir" part in the link) and then to the page which then tells me "nothing here trying there" or such which then drops me on what appears to be anish's main picasa page which then tells me that he has no public albums... i DO have a google/gmail account that i am logged into all the time and this may be a factor... another factor may be that i do not have picasa on this w2k machine... seems that "they" only support XP and Vista :rolleyes: From anishmangal2002 at gmail.com Sat Jul 11 13:24:08 2009 From: anishmangal2002 at gmail.com (Anish Mangal) Date: Sat, 11 Jul 2009 09:54:08 +0530 Subject: [ATM] Invitation to view webalbum In-Reply-To: <4A57B315.80803@windstream.net> References: <47eee29a0907100012y141de1dcg1ca2f19f7d1088bf@mail.gmail.com> <4A5791E1.4050308@windstream.net> <404750.86587.qm@web110802.mail.gq1.yahoo.com> <4A57B315.80803@windstream.net> Message-ID: <47eee29a0907102124i697a86eelfa5a41f95c29622f@mail.gmail.com> I've changed the settings to public from unlisted. Now everyone should be able to view the pics. Thanks for your interest. http://picasaweb.google.com/anishmangal2002 Anish On Sat, Jul 11, 2009 at 3:01 AM, waldo kitty wrote: > Charles Broward wrote: > >> Hi, Re Anish's link....I had to copy all three lines and paste it into my >> browser...then it went to the album. >> > > three lines? the latest thunderbird shows me one really long line... when i > click on it, the latest firefox opens and jumps thru a redirector (the > "redir" part in the link) and then to the page which then tells me "nothing > here trying there" or such which then drops me on what appears to be anish's > main picasa page which then tells me that he has no public albums... > > i DO have a google/gmail account that i am logged into all the time and > this may be a factor... another factor may be that i do not have picasa on > this w2k machine... seems that "they" only support XP and Vista :rolleyes: > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From bgilb5 at gmail.com Sat Jul 11 16:18:28 2009 From: bgilb5 at gmail.com (Brad Gilbert) Date: Sat, 11 Jul 2009 02:18:28 -0500 Subject: [ATM] Polishing First Mirror Message-ID: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> Hello, I am about 3-4 Hours into polishing my first mirror. The lines are very well defined and not jaggy or "doggybisuity". But, theres a central hill and I have a 1/4" TDE. Should I just finish polishing out or do something now to fix this? From b-hamburger at artinso.com Sat Jul 11 16:53:31 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Sat, 11 Jul 2009 09:53:31 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> Message-ID: <008201ca01fc$b0e2cb40$12a861c0$@com> What size is your mirror? I think that testing the mirror before it is fully polished is not only not helpful, but completely counterproductive. Two scenarios can arise while you test before you have fully polished: 1) Figure is very good. Result: You will feel tempted not to finish polishing in order not to spoil the good shape of the mirror. 2) Figure is defective. Result: Instead of concentrating on completely polishing, you will start corrections and eventually arrive at case 1) Both cases will leave you probably with a mirror that is not fully polished, which is why I would recommend not to test before your mirror is completely polished. The added benefit is that figuring after polishing gives you additional polishing time to really make sure you polished out all grayness. So I think you should just continue polishing. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Brad Gilbert > Sent: s?bado, 11 de julio de 2009 9:18 > To: atm at atmlist.net > Subject: [ATM] Polishing First Mirror > > Hello, I am about 3-4 Hours into polishing my first mirror. > > The lines are very well defined and not jaggy or "doggybisuity". But, > theres > a central hill and I have a 1/4" TDE. > > > Should I just finish polishing out or do something now to fix this? > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From hermit at outofoptions.org Sat Jul 11 23:17:42 2009 From: hermit at outofoptions.org (hermit) Date: Sat, 11 Jul 2009 10:17:42 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <008201ca01fc$b0e2cb40$12a861c0$@com> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> <008201ca01fc$b0e2cb40$12a861c0$@com> Message-ID: <4A589F06.3060108@outofoptions.org> Berthold Hamburger wrote: > What size is your mirror? > > I think that testing the mirror before it is fully polished is not only not > helpful, but completely counterproductive. > > Two scenarios can arise while you test before you have fully polished: > > 1) Figure is very good. Result: You will feel tempted not to finish > polishing in order not to spoil the good shape of the mirror. > 2) Figure is defective. Result: Instead of concentrating on completely > polishing, you will start corrections and eventually arrive at case 1) > > Both cases will leave you probably with a mirror that is not fully polished, > which is why I would recommend not to test before your mirror is completely > polished. The added benefit is that figuring after polishing gives you > additional polishing time to really make sure you polished out all grayness. > > So I think you should just continue polishing. > > Berthold > > I think testing early is fine so that you know if you have gross problems. Just don't let them concern you too much at this point. Ken Lowther From ericandroberta at sbcglobal.net Sat Jul 11 23:51:47 2009 From: ericandroberta at sbcglobal.net (D ERIC ALLEN) Date: Sat, 11 Jul 2009 07:51:47 -0700 (PDT) Subject: [ATM] re 24" mirror finished Message-ID: <350465.78401.qm@web80506.mail.mud.yahoo.com> Bob, et al: The outer three-quarters of the radius of the 24" mirror is pretty much flawless, aside from a couple of short scratches which my excessive figuring never quite polished out.? Near the center are some minor zones visible in both foucault and ronchi, but most of which will be covered by the secondary.? I plan to interference test the ~5" secondary against a 6" concave test plate.? Never done this, so I've been following the fluorescent light/green filter thread with great interest.? I will probably star test the secondary with the coated primary.? May have to leave Indiana to find some steady air to test it in.? I've been getting some good advice from Stan Truitt, and am always open to more. I appreciate all the kind words of encouragement. Eric From b-hamburger at artinso.com Sun Jul 12 00:59:09 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Sat, 11 Jul 2009 17:59:09 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <4A589F06.3060108@outofoptions.org> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> <008201ca01fc$b0e2cb40$12a861c0$@com> <4A589F06.3060108@outofoptions.org> Message-ID: <001501ca0240$87e27c10$97a77430$@com> Hi Ken, Obviously there are many ways that lead to good mirrors. The question to ask is, why would you test the figure of an unpolished mirror if not for saving time and correcting while polishing? Otherwise there is little point in testing, I'd say. If standard grinding techniques are followed during fine grinding, you are unlikely to arrive at a mirror shape that cannot be corrected by figuring, so my question is why bother to test for errors which you are not going to correct anyway until you completely polished the glass? Considering that a first time mirror maker is more likely to cut short on polishing time anyway and also still lacks the experience to define and apply correcting strokes for a given figure problem, I personally think the only prudent path to follow is to first polish and then worry about the figure. But then, there are so many mirrors and just as many ways to finish them... Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > > So I think you should just continue polishing. > > > > Berthold > > > > > I think testing early is fine so that you know if you have gross > problems. Just don't let them concern you too much at this point. > > Ken Lowther > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From hermit at outofoptions.org Sun Jul 12 01:45:21 2009 From: hermit at outofoptions.org (hermit) Date: Sat, 11 Jul 2009 12:45:21 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <001501ca0240$87e27c10$97a77430$@com> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> <008201ca01fc$b0e2cb40$12a861c0$@com> <4A589F06.3060108@outofoptions.org> <001501ca0240$87e27c10$97a77430$@com> Message-ID: <4A58C1A1.4070708@outofoptions.org> Berthold Hamburger wrote: > Hi Ken, > > Obviously there are many ways that lead to good mirrors. The question to ask > is, why would you test the figure of an unpolished mirror if not for saving > time and correcting while polishing? Otherwise there is little point in > testing, I'd say. > > The point isn't to test the figure though. It is a check on your technique and a look at how the glass is holding a shape. It will tell you if you polished close to a sphere. Bad stig will show. And who polishing a first mirror is going to wait until the polish is done to take a look at a Ronchi or Foucault? ;) Ken Lowther From mbartels at bbastrodesigns.com Sun Jul 12 03:08:38 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sat, 11 Jul 2009 11:08:38 -0700 Subject: [ATM] 24" mirror finished In-Reply-To: <635098.76284.qm@web80504.mail.mud.yahoo.com> References: <635098.76284.qm@web80504.mail.mud.yahoo.com> Message-ID: <00bb01ca0252$a0c8abc0$e25a0340$@com> Congratulations on a long running project! Remember you can adjust the secondary figure to help somewhat any issues on the primary. So contrive to occasionally test the two optics together. Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of D ERIC ALLEN Sent: Friday, July 10, 2009 8:38 AM To: atm at atmlist.net Subject: [ATM] 24" mirror finished For those aware of my long-running (nine years) mirror project, I have finally finished the 24" f/4 primary for my Nasmyth-style cassegrain.? The secondary is as yet unstarted.? I just turned 64 today, so lets hope it doesn't take nine years for the secondary.? R of C is 191.75".? Strehl is .994 (readings on two diameters averaged), but the individual diameters don't look that good, and as I say, I still have the secondary to do.? Anyway, I'm glad it's finished. Eric _______________________________________________ ATM mailing list http://www.atmlist.net/ From b-hamburger at artinso.com Sun Jul 12 04:17:50 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Sat, 11 Jul 2009 21:17:50 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <4A58C1A1.4070708@outofoptions.org> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> <008201ca01fc$b0e2cb40$12a861c0$@com> <4A589F06.3060108@outofoptions.org> <001501ca0240$87e27c10$97a77430$@com> <4A58C1A1.4070708@outofoptions.org> Message-ID: <001901ca025c$497c9a70$dc75cf50$@com> > -----Original Message----- > And who polishing a first mirror is going to wait until the polish is > done to take a look at a Ronchi or Foucault? ;) > Not me for sure ;-) That is exactly why I am so passionately urge our colleague to polish first and test later. I still remember my disappointment, when I got my first mirror back from coating just to find out that it was only half polished for the very reasons I gave earlier. It had a pretty good shape though and is still in use. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com From b-hamburger at artinso.com Sun Jul 12 06:58:01 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Sat, 11 Jul 2009 23:58:01 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907111328n34f8d1ej4707fb3dcd06eb64@mail.gmail.com> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> <008201ca01fc$b0e2cb40$12a861c0$@com> <4A589F06.3060108@outofoptions.org> <001501ca0240$87e27c10$97a77430$@com> <4A58C1A1.4070708@outofoptions.org> <001901ca025c$497c9a70$dc75cf50$@com> <42ee1e6c0907111328n34f8d1ej4707fb3dcd06eb64@mail.gmail.com> Message-ID: <002001ca0272$aa1a2d50$fe4e87f0$@com> What is the size of your mirror? There are a few things to watch out for while polishing and the rest you will learn by intuition. It is important to press the LAP regularly to make sure you have good contact and to trim the channels often to avoid that they close up. You should also ?microfacet? the pitch squares with a wirebrush or knife to improve on the bite. I personally do not go overboard on pressure. Pressure and control of movement should harmonize, so it is better to take it a little more easy and make sure the lap/mirror move the way you want them to. Make sure to not ?roll the edge? but rather take of a little weight towards the end of stroke and don?t extend strokes more then 1/3 over the edge. Rotate the mirror every 15-20 min. a quarter turn (not exactly ?, but rather once a little less and the other time a little more) to work against astig. There are different stroke patterns you can try etc. Don?t think too much, but rather keep the simple aim in mind to polish out the glass completely without rolling the edge and without introducing astigmatism. Taking those few precautions you will arrive there quite naturally. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com From: Brad Gilbert [mailto:bgilb5 at gmail.com] Sent: s?bado, 11 de julio de 2009 22:28 To: Berthold Hamburger Subject: Re: [ATM] Polishing First Mirror I agree. I am just going to polish out and ignore the Ronchigram, I'll take a look now and then to make sure it is not too far off. I've searched the internet a lot about pages on polishing but can't find much. Do you guys have any tips on the stroke. Is slow with tons of pressure better? I usually put lots of pressure on the mirror and one stroke takes about 3 seconds. If I try and go faster the mirror usually can't be controlled to go straight. I'm using Gugolz #64, but I live in a rather hot and humid climate. Is working in 80-90F weather okay or will this make it harder on myself? On Sat, Jul 11, 2009 at 2:17 PM, Berthold Hamburger wrote: > -----Original Message----- > And who polishing a first mirror is going to wait until the polish is > done to take a look at a Ronchi or Foucault? ;) > Not me for sure ;-) That is exactly why I am so passionately urge our colleague to polish first and test later. I still remember my disappointment, when I got my first mirror back from coating just to find out that it was only half polished for the very reasons I gave earlier. It had a pretty good shape though and is still in use. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com _______________________________________________ ATM mailing list http://www.atmlist.net/ From rmay at nethere.com Sun Jul 12 08:00:48 2009 From: rmay at nethere.com (Bob May) Date: Sat, 11 Jul 2009 16:00:48 -0700 Subject: [ATM] Polishing First Mirror References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> Message-ID: <002101ca027b$6efa2280$33fe1345@amd> There's two ways to insure that the edge gets polished. First is to keep on going and hopefully, the edge will catch up to the center. Shorter strokes, to a degree, will keep the ROC from shrinking too fast. The other is to turn the mirror and lap over and work that way. That way, you will tend to work the edge more than the center and thus you will quickly get the edge polished out. Remember that where you abrade the surface, that is where the surface gets eroded away. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From milliesand at cox.net Sun Jul 12 08:13:35 2009 From: milliesand at cox.net (Tom and Beth) Date: Sat, 11 Jul 2009 16:13:35 -0700 Subject: [ATM] ATM] Baader 9X60mm finder telescope References: Message-ID: <3A68B9A4FECC409480B1C59D59AEA5EF@2a5e290d848764> I'm using the 8x50MM brother to it and it is sold with TEC scopes. VERY sharp finder...better than a Stellavue "Sparrowhalk:" with a TV 15MM Plossl if that helps. Tom From baldjeff at comcast.net Sun Jul 12 09:07:21 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Sat, 11 Jul 2009 17:07:21 -0700 Subject: [ATM] astigmatism tests Message-ID: Hi ATMers: I am about 2 hours in to polishing a 24" f/3.6, the thickness at the edge is about 1.35". I am astigmatism testing before I continue. The mirror was mounted on two sheets of 3/4" plywood with a 1" strap contacting the mirror for about 140 degrees. Short pile carpet supports the mirror against the plywood. The vertical diameter has an ROC a bit longer than the horizontal diameter. I rotated the mirror 90 degrees, and again, the ROC is a bit longer on the vertical axis. Since the astigmatism did not rotate, my mirror holder is bending the glass. I then whipped up a 9-pt flotation cell for the mirror stand, and again, the vertical axis is a bit longer than the horizontal axis regardless of mirror orientation. So I eliminated the back support. I would like to confirm that I have no astigmatism in the glass. Seeing that my mount creates astigmatism does not mean that my mirror has none. But I need to elliminate this system error. I have heard urban legends regarding how many degrees the strap should contact the mirror, anywhere form 180 degrees, to 160 to 170, and many other ideas. I know that when I pose this question to the group I will get even more of these answers. Nonetheless, I am asking two questions. First, what is the concensus on degrees of contact for the strap, and second, how close to the front edge and back edge ought the strap stay back from. Meanwhile I am going to support the edge with about 170 degrees of contact and possibly use a thinner strap, and I will let you know what the results are. Thanks, will enjoy hearing from all of you. Bald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org From mbartels at bbastrodesigns.com Sun Jul 12 10:32:25 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sat, 11 Jul 2009 18:32:25 -0700 Subject: [ATM] astigmatism tests In-Reply-To: References: Message-ID: <007201ca0290$a0838340$e18a89c0$@com> >>>First, what is the concensus on degrees of contact for the strap, and second, how close to the front edge and back edge ought the strap stay back from. Meanwhile I am going to support the edge with about 170 degrees of contact and possibly use a thinner strap, and I will let you know what the results are. Rather than consensus, can I interest you in studies done for the largest scopes in the world? Wilson's Reflecting Telescope Optics reviews studies that compare various strap radii and shows that 180 degree is the best. An amateur version is at http://www.cruxis.com/scope/mirroredgecalculator.htm Finally, how about no strap at all? I haven't used straps for a dozen years. As Wilson points out, two points *exactly* at 90 degree separation is a simpler and attractive alternative. Mel Bartels From alaskawolfjoe at hotmail.com Sun Jul 12 11:06:13 2009 From: alaskawolfjoe at hotmail.com (lance clarke) Date: Sat, 11 Jul 2009 22:06:13 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <001901ca025c$497c9a70$dc75cf50$@com> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> <008201ca01fc$b0e2cb40$12a861c0$@com> <4A589F06.3060108@outofoptions.org> <001501ca0240$87e27c10$97a77430$@com> <4A58C1A1.4070708@outofoptions.org> <001901ca025c$497c9a70$dc75cf50$@com> Message-ID: I never had a problem with fully polishing a mirror. First I polish it until I think it is polished out, then I spend about 4X that amount of time figuring. Really. That being said, I agree with some of the others that you should first concentrate on getting a complete polish before worrying about the figure. Test for satisfaction of your curiosity, but just keep polishing with good technique until it passes the laser test. Then do some more for good measure. Then test, and figure. Repeat until done. In my case, repeat endlessly. It may take a little longer, but "what is a hobby, except a way to murder time". Lance > From: b-hamburger at artinso.com > To: hermit at outofoptions.org > Date: Sat, 11 Jul 2009 21:17:50 +0200 > CC: atm at atmlist.net > Subject: Re: [ATM] Polishing First Mirror > > > > -----Original Message----- > > And who polishing a first mirror is going to wait until the polish is > > done to take a look at a Ronchi or Foucault? ;) > > > > Not me for sure ;-) > That is exactly why I am so passionately urge our colleague to polish first > and test later. I still remember my disappointment, when I got my first > mirror back from coating just to find out that it was only half polished for > the very reasons I gave earlier. It had a pretty good shape though and is > still in use. > > Berthold > -- > Berthold Hamburger - Cellist/Spain > Email: behambu at artinso.com > http://www.artinso.com > http://www.astro.artinso.com > > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ _________________________________________________________________ We are your photos. Share us now with Windows Live Photos. http://go.microsoft.com/?linkid=9666047 From baldjeff at comcast.net Sun Jul 12 12:28:03 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Sat, 11 Jul 2009 20:28:03 -0700 Subject: [ATM] astigmatism tests References: <007201ca0290$a0838340$e18a89c0$@com> Message-ID: Thanks Mel. As usual, very awesome. JBald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org ----- Original Message ----- From: "Mel Bartels" To: "'atm'" Sent: Saturday, July 11, 2009 6:32 PM Subject: Re: [ATM] astigmatism tests >>>>First, what is the concensus on degrees of contact for the strap, and > second, how close to the front edge and back edge ought the strap stay > back > from. Meanwhile I am going to support the edge with about 170 degrees of > contact and possibly use a thinner strap, and I will let you know what the > results are. > > > Rather than consensus, can I interest you in studies done for the largest > scopes in the world? Wilson's Reflecting Telescope Optics reviews studies > that compare various strap radii and shows that 180 degree is the best. > An > amateur version is at http://www.cruxis.com/scope/mirroredgecalculator.htm > > Finally, how about no strap at all? I haven't used straps for a dozen > years. As Wilson points out, two points *exactly* at 90 degree separation > is a simpler and attractive alternative. > > Mel Bartels > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From robert.houdart at cruxis.be Sun Jul 12 19:42:22 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Sun, 12 Jul 2009 12:42:22 +0200 Subject: [ATM] astigmatism tests In-Reply-To: Message-ID: Jeff, > First, what is the concensus on degrees of contact for > the strap, and second, how close to the front edge and > back edge ought the strap stay back from. There's been some progress lately, science and engineering have replaced the "urban legends" ;). See the Mirror Edge Support Calculator at http://www.cruxis.com/scope/mirroredgecalculator.htm A sling should contact the mirror for 180 degrees and should be placed at the center of gravity (COG) of the mirror. >From the description you gave, I think the astigmatism is mostly related to not supporting the mirror at its COG. You may consider switching to a steel cable because it gives a thin contact line that can be positioned accurately on the edge of the mirror. An alternative and somewhat simpler solution is two pegs or roller bearings separated by 90?, once again to be placed accurately at the COG of the mirror. Please let us know your results after improving the edge support! Cheers, Robert Houdart http://www.cruxis.com From baldjeff at comcast.net Mon Jul 13 02:20:53 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Sun, 12 Jul 2009 10:20:53 -0700 Subject: [ATM] astigmatism tests References: <007201ca0290$a0838340$e18a89c0$@com> Message-ID: Hi gang; I slung the mirror with 180 degrees of sling contact, and still, there is longer ROC on the vertical diameter than on the horizontal diameter no matter which way the mirror goes in. I guess my next step is to use a wire instead of a strap. The strap I'm using is a 1" mountaineering strap, so since my mirror is so thin it may be contacting too much of my side. I did enjoy the mirror edge calculator. The mirror is nearly horizontal, so I may try it with an upward optical axis to move weight onto the back instead on just the side. Perhaps a mirror this thin needs to only look upward higher than a particular altitude and any lower than that creates difficulties. Any more suggestions are welcome. I'll let you know how the wire works. JBald > Wilson's Reflecting Telescope Optics reviews studies > that compare various strap radii and shows that 180 degree is the best. > An > amateur version is at http://www.cruxis.com/scope/mirroredgecalculator.htm > > Mel Bartels > From robert.houdart at cruxis.be Mon Jul 13 05:43:47 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Sun, 12 Jul 2009 22:43:47 +0200 Subject: [ATM] astigmatism tests In-Reply-To: Message-ID: Jeff, > Perhaps a mirror this thin needs to only look upward higher > than a particular altitude and any lower than that creates > difficulties. Even as high as 45? altitude you still have 70% of the load on the edge support, so you'll still find 70% of astigmatism. Robert From wkitty42 at windstream.net Mon Jul 13 06:19:10 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Sun, 12 Jul 2009 17:19:10 -0400 Subject: [ATM] astigmatism tests In-Reply-To: References: Message-ID: <4A5A534E.3000204@windstream.net> Robert Houdart wrote: > A sling should contact the mirror for 180 degrees and should be placed at > the center of gravity (COG) of the mirror. can we get a small bit of clarification on this statement, please? does this mean the COG of the /thickness/ of the mirror?? >>From the description you gave, I think the astigmatism is mostly related to > not supporting the mirror at its COG. You may consider switching to a steel > cable because it gives a thin contact line that can be positioned accurately > on the edge of the mirror. > > An alternative and somewhat simpler solution is two pegs or roller bearings > separated by 90?, once again to be placed accurately at the COG of the > mirror. i'm not sure i understand this part, either... i can see two pegs or roller bearings but i can't visualize how they can be placed at the COG of the /thickness/ of the mirror if they are mounted to the mirror's backing... mono-spaced ascii drawing: _ | || | || | || |==| <-- holding peg | || |m|| surface -> |i|| |r|| <-- back mount |r|| |o|| |r|| | || | || |_|| visualize this as a 1 inch thick mirror mounted .125 inch off the back mount which is .25 inches thick... i'm seeing the pegs as being about 1.125 inches long such that their top comes flush to or just barely over the top edge of the mirror surface and their bottom is "flush" with the mirror side of the back mount... yes, this is a very simple vision and ascii drawings still suxorz :? From robert.houdart at cruxis.be Mon Jul 13 07:20:52 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 13 Jul 2009 00:20:52 +0200 Subject: [ATM] astigmatism tests In-Reply-To: <4A5A534E.3000204@windstream.net> Message-ID: Waldo, > does this mean the COG of the /thickness/ of the mirror?? Yes, COG measured over the thickness of the mirror. This value is computed by the Mirror Edge Support Calculator, for Jeff's 24"x1.35 f/3.6 mirror the COG is at 0.58 inch from the mirror back. > i'm not sure i understand this part, either... i can see > two pegs or roller bearings but i can't visualize how they > can be placed at the COG of the /thickness/ of the mirror > if they are mounted to the mirror's backing... Roller bearings are the easier solution, mounted so that they can roll vertically on the mirror edge. A fine example from a 16 inch scope on Jan Van Gastel's web site: http://members.ziggo.nl/jhm.vangastel/Astronomy/50cmscope/plaatjes50cm/lager blok.jpg You can also use cheap plastic rollers, as in my most recent 16" scope: http://www.cruxis.com/scope/img/406_NewMirrorCell.jpg The roller bearings create a contact point on the mirror edge which can be accurately measured. Unlike sling or cable supports, you'll never have any out-of-plane forces nor any sideway movement of the mirror. A very effective solution! Hope this helps, Robert From TPolk at decatur-al.gov Mon Jul 13 11:16:54 2009 From: TPolk at decatur-al.gov (Polk, Tom) Date: Sun, 12 Jul 2009 21:16:54 -0500 Subject: [ATM] astigmatism tests References: Message-ID: <398213C674F7554AB0F55401DF29FBD10139A756@ziggy.decatur-al.net> Hello, Does the position of the roller bearings change when you collimate the telescope? Thanks, Tom Roller bearings are the easier solution, mounted so that they can roll vertically on the mirror edge. A fine example from a 16 inch scope on Jan Van Gastel's web site: http://members.ziggo.nl/jhm.vangastel/Astronomy/50cmscope/plaatjes50cm/lager blok.jpg You can also use cheap plastic rollers, as in my most recent 16" scope: http://www.cruxis.com/scope/img/406_NewMirrorCell.jpg The roller bearings create a contact point on the mirror edge which can be accurately measured. Unlike sling or cable supports, you'll never have any out-of-plane forces nor any sideway movement of the mirror. A very effective solution! Hope this helps, Robert _______________________________________________ ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Mon Jul 13 12:05:00 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Sun, 12 Jul 2009 20:05:00 -0700 Subject: [ATM] Polishing First Mirror In-Reply-To: <008201ca01fc$b0e2cb40$12a861c0$@com> Message-ID: You are reminding me of the Los Angeles Astronomical Society (LAAS) workshop in the early 1970's. That was before they were kicked out of the Griffith Observatory basement. There was a lot of activity: you could go there three nights a week. But the atmosphere was very authoritarian. John Dobson was just getting started, and his scopes were dissed everywhere, no matter how good their images. Any deviation from the the Ingals 3 volume set would result in the warning, "Your methods may work, but we can not tolerate you setting a bad example for beginners here." If you continued your deviant behavior, you would be expelled from the workshop. The shop director, a goateed beatnik character, had a girlfriend named Trudy who was almost the most perfect thing that ever lived. She went on to join the editorial staffs of Scientific American and IEEE Spectrum. I'm sure she is an old lady by now. That's how it was in 1971. Never again. At least I had hair on my head back then. The advantage of a crude test before polishing is that sometimes ground surfaces have imperfections that can only be polished out with a billion years of polishing. If you detect those problems early, you can correct them by more grinding and not waste time polishing. One good test of unpolished surfaces is the blind test. I have already made this known to a few deserving heretics, so the knowledge will not perish when I am gone. None of this has anything to do with top secret airship LZ-137, except that there was one crazy Nazi who there who was always working on a mirror... -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Berthold Hamburger Sent: Saturday, July 11, 2009 12:54 AM To: 'Brad Gilbert' Cc: atm at atmlist.net Subject: Re: [ATM] Polishing First Mirror What size is your mirror? I think that testing the mirror before it is fully polished is not only not helpful, but completely counterproductive. Two scenarios can arise while you test before you have fully polished: 1) Figure is very good. Result: You will feel tempted not to finish polishing in order not to spoil the good shape of the mirror. 2) Figure is defective. Result: Instead of concentrating on completely polishing, you will start corrections and eventually arrive at case 1) Both cases will leave you probably with a mirror that is not fully polished, which is why I would recommend not to test before your mirror is completely polished. The added benefit is that figuring after polishing gives you additional polishing time to really make sure you polished out all grayness. So I think you should just continue polishing. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On > Behalf Of Brad Gilbert > Sent: s?bado, 11 de julio de 2009 9:18 > To: atm at atmlist.net > Subject: [ATM] Polishing First Mirror > > Hello, I am about 3-4 Hours into polishing my first mirror. > > The lines are very well defined and not jaggy or "doggybisuity". But, > theres a central hill and I have a 1/4" TDE. > > > Should I just finish polishing out or do something now to fix this? > _______________________________________________ > ATM mailing list http://www.atmlist.net/ _______________________________________________ ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Mon Jul 13 12:58:15 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Sun, 12 Jul 2009 20:58:15 -0700 Subject: [ATM] astigmatism tests In-Reply-To: <007201ca0290$a0838340$e18a89c0$@com> Message-ID: How do you know that two points, exactly 90 degrees apart, are the best you can do? My mirror mounts don't have any edge supports at all, and they work OK. -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Mel Bartels Sent: Saturday, July 11, 2009 6:32 PM To: 'atm' Subject: Re: [ATM] astigmatism tests >>>First, what is the concensus on degrees of contact for the strap, and second, how close to the front edge and back edge ought the strap stay back from. Meanwhile I am going to support the edge with about 170 degrees of contact and possibly use a thinner strap, and I will let you know what the results are. Rather than consensus, can I interest you in studies done for the largest scopes in the world? Wilson's Reflecting Telescope Optics reviews studies that compare various strap radii and shows that 180 degree is the best. An amateur version is at http://www.cruxis.com/scope/mirroredgecalculator.htm Finally, how about no strap at all? I haven't used straps for a dozen years. As Wilson points out, two points *exactly* at 90 degree separation is a simpler and attractive alternative. Mel Bartels _______________________________________________ ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Mon Jul 13 13:03:08 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Sun, 12 Jul 2009 21:03:08 -0700 Subject: [ATM] astigmatism tests In-Reply-To: Message-ID: I suggest that you glue the mirror to a stiff metal plate so that it can not flex. Just use a very thin layer of epoxy, and slide to mirror around a bit before the epoxy gets stiff. Be sure that the glue layer is thin and that there are no air bubbles in it behind the mirror. You will get better adhesion if the back of the mirror is fine ground on the same metal plate it is to be bonded to. Then you should add mirror clips around the edge, and make them really tight, for safety and to assure that nothing will rattle loose in there. -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Jeff Baldwin Sent: Saturday, July 11, 2009 5:07 PM To: atm Subject: [ATM] astigmatism tests Hi ATMers: I am about 2 hours in to polishing a 24" f/3.6, the thickness at the edge is about 1.35". I am astigmatism testing before I continue. The mirror was mounted on two sheets of 3/4" plywood with a 1" strap contacting the mirror for about 140 degrees. Short pile carpet supports the mirror against the plywood. The vertical diameter has an ROC a bit longer than the horizontal diameter. I rotated the mirror 90 degrees, and again, the ROC is a bit longer on the vertical axis. Since the astigmatism did not rotate, my mirror holder is bending the glass. I then whipped up a 9-pt flotation cell for the mirror stand, and again, the vertical axis is a bit longer than the horizontal axis regardless of mirror orientation. So I eliminated the back support. I would like to confirm that I have no astigmatism in the glass. Seeing that my mount creates astigmatism does not mean that my mirror has none. But I need to elliminate this system error. I have heard urban legends regarding how many degrees the strap should contact the mirror, anywhere form 180 degrees, to 160 to 170, and many other ideas. I know that when I pose this question to the group I will get even more of these answers. Nonetheless, I am asking two questions. First, what is the concensus on degrees of contact for the strap, and second, how close to the front edge and back edge ought the strap stay back from. Meanwhile I am going to support the edge with about 170 degrees of contact and possibly use a thinner strap, and I will let you know what the results are. Thanks, will enjoy hearing from all of you. Bald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org _______________________________________________ ATM mailing list http://www.atmlist.net/ From gfbrandenburg at yahoo.com Mon Jul 13 13:09:51 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Sun, 12 Jul 2009 21:09:51 -0700 (PDT) Subject: [ATM] astigmatism tests In-Reply-To: Message-ID: <40146.30120.qm@web111505.mail.gq1.yahoo.com> Richard, Are you serious, or joking? Hard to tell sometimes. Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Mon, 7/13/09, Richard Schwartz wrote: > From: Richard Schwartz > Subject: Re: [ATM] astigmatism tests > To: "'Jeff Baldwin'" , "'atm'" > Date: Monday, July 13, 2009, 12:03 AM > I suggest that you glue the mirror to > a stiff metal plate so that it can not > flex.? Just use a very thin layer of epoxy, and slide > to mirror around a bit > before the epoxy gets stiff. Be sure that the glue layer is > thin and that > there are no air bubbles in it behind the mirror.? You > will get better > adhesion if the back of the mirror is fine ground on the > same metal plate it > is to be bonded to.? Then you should add mirror clips > around the edge, and > make them really tight, for safety and to assure that > nothing will rattle > loose in there.??? > > -----Original Message----- > From: atm-bounces at atmlist.net > [mailto:atm-bounces at atmlist.net] > On Behalf Of > Jeff Baldwin > Sent: Saturday, July 11, 2009 5:07 PM > To: atm > Subject: [ATM] astigmatism tests > > > Hi ATMers: > I am about 2 hours in to polishing a 24" f/3.6, the > thickness at the edge is > about 1.35". I am astigmatism testing before I continue. > The mirror was > mounted on two sheets of 3/4" plywood with a 1" strap > contacting the mirror > for about 140 degrees. Short pile carpet supports the > mirror against the > plywood. > > The vertical diameter has an ROC a bit longer than the > horizontal diameter. > I rotated the mirror 90 degrees, and again, the ROC is a > bit longer on the > vertical axis. Since the astigmatism did not rotate, my > mirror holder is > bending the glass. > > I then whipped up a 9-pt flotation cell for the mirror > stand, and again, the > vertical axis is a bit longer than the horizontal axis > regardless of mirror > orientation. So I eliminated the back support. I would like > to confirm that > I have no astigmatism in the glass. Seeing that my mount > creates astigmatism > does not mean that my mirror has none. But I need to > elliminate this system > error. > > I have heard urban legends regarding how many degrees the > strap should > contact the mirror, anywhere form 180 degrees, to 160 to > 170, and many other > ideas. I know that when I pose this question to the group I > will get even > more of these answers. Nonetheless, I am asking two > questions. First, what > is the concensus on degrees of contact for the strap, and > second, how close > to the front edge and back edge ought the strap stay back > from. Meanwhile I > am going to support the edge with about 170 degrees of > contact and possibly > use a thinner strap, and I will let you know what the > results are. > > Thanks, will enjoy hearing from all of you. > Bald > > Jeff and Glenda Baldwin > Lathrop, CA > www.stocktonastro.org > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mbartels at bbastrodesigns.com Mon Jul 13 14:38:32 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sun, 12 Jul 2009 22:38:32 -0700 Subject: [ATM] astigmatism tests In-Reply-To: References: <007201ca0290$a0838340$e18a89c0$@com> Message-ID: <016f01ca037c$2da61e90$88f25bb0$@com> How do you go from, " simpler and attractive alternative" to " are the best you can do"? Mel Bartels -----Original Message----- From: Richard Schwartz [mailto:richard1941 at gmail.com] Sent: Sunday, July 12, 2009 8:58 PM To: 'Mel Bartels'; 'atm' Subject: RE: [ATM] astigmatism tests How do you know that two points, exactly 90 degrees apart, are the best you can do? My mirror mounts don't have any edge supports at all, and they work OK. -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Mel Bartels Sent: Saturday, July 11, 2009 6:32 PM To: 'atm' Subject: Re: [ATM] astigmatism tests >>>First, what is the concensus on degrees of contact for the strap, and second, how close to the front edge and back edge ought the strap stay back from. Meanwhile I am going to support the edge with about 170 degrees of contact and possibly use a thinner strap, and I will let you know what the results are. Rather than consensus, can I interest you in studies done for the largest scopes in the world? Wilson's Reflecting Telescope Optics reviews studies that compare various strap radii and shows that 180 degree is the best. An amateur version is at http://www.cruxis.com/scope/mirroredgecalculator.htm Finally, how about no strap at all? I haven't used straps for a dozen years. As Wilson points out, two points *exactly* at 90 degree separation is a simpler and attractive alternative. Mel Bartels _______________________________________________ ATM mailing list http://www.atmlist.net/ From toolontop at yahoo.com Mon Jul 13 17:04:00 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Mon, 13 Jul 2009 01:04:00 -0700 (PDT) Subject: [ATM] astigmatism tests In-Reply-To: Message-ID: <734485.93509.qm@web112414.mail.gq1.yahoo.com> I've no idea how you can get somebody to supply a consensus on this, but FWIW I'll say that you're doing a couple things wrong supporting this 18:1 mirror this way on the test stand. A lot of experimentation zeroed in on the best test stand support for thin mirrors: 1) Lose the strap, use pegs where the pegs have a grommet or similar fitting falling just outside the COG of the glass disk, oriented at 90 degrees supporting the base of the glass. 2) No flexible back (carpet or cell), they don't do squat for vertical testing. Produce a reasonably flat back support into which the pegs insert in 90 degree holes, the support can be made of something like 1/2" Corian countertop against a solid backer (this is what I'm using up to 20"), whatever it is it must be quite flat and the back of the mirror likewise. Then the mirror is just placed onto the backing and lowered into contact with the grommets on the pegs gently, with no other pressure involved. The large contact area of the back plus the small contact area on the pegs easily counteracts the potato chipping you're seeing from the combo of sling/carpet or sling/cell - I've seen this happen in experimenting with supporting _full thick_ 12.5" Pyrex variously on a sling/foam/bubble wrap... With proper support the mirror can't bend over because it's prevented from this by the back support, and it can't bend forward at the base because it's held by the contact points. Neither are true with slings and flexible back supports. This setup allows me to easily verify lack of astigmatism in mirrors down to about 20:1 aspect ratio, using a precision pinhole source and a 12mm EP to view the resulting pattern through the caustic. Here's a picture of what I'm talking about with the pegs (I put some vinyl hose behind the grommets to ensure alignment as needed): http://www.raddobs.com/atm/peg%20support.jpg Best, Mark --- On Sat, 7/11/09, Jeff Baldwin wrote: > From: Jeff Baldwin > Subject: [ATM] astigmatism tests > To: "atm" > Date: Saturday, July 11, 2009, 5:07 PM > Hi ATMers: > I am about 2 hours in to polishing a 24" f/3.6, the > thickness at the edge is about 1.35". I am astigmatism > testing before I continue. The mirror was mounted on two > sheets of 3/4" plywood with a 1" strap contacting the mirror > for about 140 degrees. Short pile carpet supports the mirror > against the plywood. > > The vertical diameter has an ROC a bit longer than the > horizontal diameter. I rotated the mirror 90 degrees, and > again, the ROC is a bit longer on the vertical axis. Since > the astigmatism did not rotate, my mirror holder is bending > the glass. > > I then whipped up a 9-pt flotation cell for the mirror > stand, and again, the vertical axis is a bit longer than the > horizontal axis regardless of mirror orientation. So I > eliminated the back support. I would like to confirm that I > have no astigmatism in the glass. Seeing that my mount > creates astigmatism does not mean that my mirror has none. > But I need to elliminate this system error. > > I have heard urban legends regarding how many degrees the > strap should contact the mirror, anywhere form 180 degrees, > to 160 to 170, and many other ideas. I know that when I pose > this question to the group I will get even more of these > answers. Nonetheless, I am asking two questions. First, what > is the concensus on degrees of contact for the strap, and > second, how close to the front edge and back edge ought the > strap stay back from. Meanwhile I am going to support the > edge with about 170 degrees of contact and possibly use a > thinner strap, and I will let you know what the results > are. > > Thanks, will enjoy hearing from all of you. > Bald > > Jeff and Glenda Baldwin > Lathrop, CA > www.stocktonastro.org > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From b-hamburger at artinso.com Mon Jul 13 17:05:55 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Mon, 13 Jul 2009 10:05:55 +0200 Subject: [ATM] astigmatism tests In-Reply-To: References: Message-ID: <006901ca0390$c0ba01b0$422e0510$@com> Richard, That reminds me of an advice you gave to an aspiring telescope maker some 10-12 years ago about making a pitch lap. If I remember correctly, the poor lad was told to boil turpentine on the kitchen stove before mixing it with pitch in order to make his first (and probably last) polishing lap. Anyway, I think he was told (just) in time that your suggestion was a hoax and lives happily ever since.... I guess no rescuer is needed presently, but maybe we could agree on a secret moniker to safely identify and separate hoax from true wisdom. After all, all those messages end up in the archives and some poor guy might really end up cementing his glass to a metal backing one day, because he read your message out of context. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Richard Schwartz > Sent: lunes, 13 de julio de 2009 6:03 > To: 'Jeff Baldwin'; 'atm' > Subject: Re: [ATM] astigmatism tests > > I suggest that you glue the mirror to a stiff metal plate so that it can > not > flex. Just use a very thin layer of epoxy, and slide to mirror around a > bit > before the epoxy gets stiff. Be sure that the glue layer is thin and > that > there are no air bubbles in it behind the mirror. You will get better > adhesion if the back of the mirror is fine ground on the same metal > plate it > is to be bonded to. Then you should add mirror clips around the edge, > and > make them really tight, for safety and to assure that nothing will > rattle > loose in there. > > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of > Jeff Baldwin > Sent: Saturday, July 11, 2009 5:07 PM > To: atm > Subject: [ATM] astigmatism tests > > > Hi ATMers: > I am about 2 hours in to polishing a 24" f/3.6, the thickness at the > edge is > about 1.35". I am astigmatism testing before I continue. The mirror was > mounted on two sheets of 3/4" plywood with a 1" strap contacting the > mirror > for about 140 degrees. Short pile carpet supports the mirror against the > plywood. > > The vertical diameter has an ROC a bit longer than the horizontal > diameter. > I rotated the mirror 90 degrees, and again, the ROC is a bit longer on > the > vertical axis. Since the astigmatism did not rotate, my mirror holder is > bending the glass. > > I then whipped up a 9-pt flotation cell for the mirror stand, and again, > the > vertical axis is a bit longer than the horizontal axis regardless of > mirror > orientation. So I eliminated the back support. I would like to confirm > that > I have no astigmatism in the glass. Seeing that my mount creates > astigmatism > does not mean that my mirror has none. But I need to elliminate this > system > error. > > I have heard urban legends regarding how many degrees the strap should > contact the mirror, anywhere form 180 degrees, to 160 to 170, and many > other > ideas. I know that when I pose this question to the group I will get > even > more of these answers. Nonetheless, I am asking two questions. First, > what > is the concensus on degrees of contact for the strap, and second, how > close > to the front edge and back edge ought the strap stay back from. > Meanwhile I > am going to support the edge with about 170 degrees of contact and > possibly > use a thinner strap, and I will let you know what the results are. > > Thanks, will enjoy hearing from all of you. > Bald > > Jeff and Glenda Baldwin > Lathrop, CA > www.stocktonastro.org _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From toolontop at yahoo.com Mon Jul 13 17:16:16 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Mon, 13 Jul 2009 01:16:16 -0700 (PDT) Subject: [ATM] sapphire coating was Tessellated Mirror Picture Message-ID: <589911.24988.qm@web112420.mail.gq1.yahoo.com> Followup: I've tested this 14.7" f/6.6 quartz part now before and after removing the sapphire coating from the back. There was no visible strain with it in place, and no visible strain with it removed, to the limits of the crossed polarizers. When I removed the coating from the back via fine grinding two things happened - the edge bent up slightly making it take the longest to remove the coating from, and the ROC of the mirror on the other side shrank by about 2%. All curious, but repeatable and agrees with prior experience. Best, Mark --- On Wed, 7/1/09, Mark Cowan wrote: > In this case, the blank came with sapphire coatings on both > side.? One side was generated and worked as normal, > until IIRC it tested finished.? At that point I clean > up the edges and back if needed, and due to some scratching > on the back I elected to fine grind that by hand - but the > grit wouldn't even touch it under hand pressure.? I put > it on the machine to go at either 320 or 500 SiC and > finished with some AlOx around 25 micron to get a nice > smooth surface.? Normally that would have no > appreciable effect on the figure.? I put it on the test > stand and it looked fine at first under Ronchi, but then I > measured it and found 120% correction!? Had to take it > back and start over.? Sorry, I don't recall exactly if > the correction was the same zone-zone, but it looked very > nice under Ronchi and, as I said, had tested finished before > at 100% correction. > > I can only attribute it to the sapphire coating.? I > didn't test it for strain specifically, but I have an f/6.6 > in process that has sapphire on the back and will be going > into polishing - so I'll check it for strain before and > after I take the coating off the back of that one (prior to > figuring!!). > > Best, > Mark > > --- On Tue, 6/30/09, Richard Schwartz > wrote: > > > From: Richard Schwartz > > Subject: Re: [ATM] Tessellated Mirror Picture > > To: "wkitty42 at windstream.net" > > > Cc: "atm at atmlist.net" > > > Date: Tuesday, June 30, 2009, 11:50 PM > > How did you remove the coating ok the > > back?? If by grinding, maybe the coating had nothing > to > > do with it.? Also, how did the glass look between > > crossed polorrhoids before you removed the back > > coating?? (sorry, I'm just trying to keep you > honest) > > > > Sent from my iPhone > > > > On Jun 30, 2009, at 14:46, waldo kitty > > wrote: > > > > > Mark Cowan wrote: > > >> I recently had a 14.7x.8" f/4.2 quartz > mirror > > (finished!) gain 20% correction overall when I removed > a > > slightly scratched sapphire coating from the bank of > the > > blank! > > > > > > from the /back/ of the mirror? > > > > > > that would seem to indicate that it was causing > the > > mirror to flex and not be properly flat... > interesting... > > very interesting... > > > > > > --? ? ? _\/ > > >? ? ? (@@)? ? ? ? > > ? ? ? ? ? ? ? Waldo > > Kitty, Waldo's Place USA > > > __ooO_( )_Ooo_____________________ > > telnet://bbs.wpusa.dynip.com > > > _|_____|_____|_____|_____|_____|_____ http://www.wpusa.dynip.com > > > ____|_____|_____|_____|_____|_____|____ ftp://ftp.wpusa.dynip.com > > > _|_Eat_SPAM_to_email_me!_YUM!__|_____ wkitty42 > -at- > > windstream.net > > > _______________________________________________ > > > ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > > > > > From bgilb5 at gmail.com Mon Jul 13 17:37:00 2009 From: bgilb5 at gmail.com (Brad Gilbert) Date: Mon, 13 Jul 2009 03:37:00 -0500 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907122149y3f255edcpbb7ef47fa05d0e3f@mail.gmail.com> References: <008201ca01fc$b0e2cb40$12a861c0$@com> <42ee1e6c0907122149y3f255edcpbb7ef47fa05d0e3f@mail.gmail.com> Message-ID: <42ee1e6c0907130137p1f0fcdffl75caab2033e08230@mail.gmail.com> I made some great progress today! After several failure 2+ sessions which saw no progress, I decided to take action and modify my pitch lap. I made the channels much deeper with a triangle ruler and a blow drier. This led to contact being terrible so I warm pressed with this cloth mesh I found for an hour or two. The texture makes such a big difference, it's insane! I had about a 60% pit reduction in the center in one 15 minute session. Compared to like 0% for 4 hours this is great. There is still contact issues as the center is having some sphere in a sphere sorta thing going on. I'm warm pressing right now again with more weight so we'll see where that gets me. On Sun, Jul 12, 2009 at 11:49 PM, Brad Gilbert wrote: > Your stories are great Richard. > > I'm sorry I am very new to this forum, I should have provided more > information, obviously I am a little naive about how things work around > here. > > Its a 12" mirror. The focal length is almost exactly 60" making it f/5. The > tester I made is a Ronchi tester. Everything is on the same moving carrier. > > One problem I am having with my pitch lap is that even in 78-80F weather, > my finger nail sinks in almost instantly and the channels and faceting close > up fairly quickly. I even went through the trouble of boiling the pitch > before making the lap, knowing full well the weather here was a bit warm. > > Thank you guys. I'm not really worried about the tests right now as you > guys have said I shouldn't. > > > > On Sun, Jul 12, 2009 at 10:05 PM, Richard Schwartz wrote: > >> You are reminding me of the Los Angeles Astronomical Society (LAAS) >> workshop >> in the early 1970's. That was before they were kicked out of the >> Griffith >> Observatory basement. There was a lot of activity: you could go there >> three nights a week. But the atmosphere was very authoritarian. John >> Dobson was just getting started, and his scopes were dissed everywhere, no >> matter how good their images. Any deviation from the the Ingals 3 volume >> set would result in the warning, "Your methods may work, but we can not >> tolerate you setting a bad example for beginners here." If you continued >> your deviant behavior, you would be expelled from the workshop. The shop >> director, a goateed beatnik character, had a girlfriend named Trudy who >> was >> almost the most perfect thing that ever lived. She went on to join the >> editorial staffs of Scientific American and IEEE Spectrum. I'm sure she >> is >> an old lady by now. >> >> That's how it was in 1971. Never again. At least I had hair on my head >> back then. >> >> The advantage of a crude test before polishing is that sometimes ground >> surfaces have imperfections that can only be polished out with a billion >> years of polishing. If you detect those problems early, you can correct >> them by more grinding and not waste time polishing. One good test of >> unpolished surfaces is the blind test. I have already made this known to >> a >> few deserving heretics, so the knowledge will not perish when I am gone. >> >> None of this has anything to do with top secret airship LZ-137, except >> that >> there was one crazy Nazi who there who was always working on a mirror... >> >> >> >> >> -----Original Message----- >> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf >> Of >> Berthold Hamburger >> Sent: Saturday, July 11, 2009 12:54 AM >> To: 'Brad Gilbert' >> Cc: atm at atmlist.net >> Subject: Re: [ATM] Polishing First Mirror >> >> >> What size is your mirror? >> >> I think that testing the mirror before it is fully polished is not only >> not >> helpful, but completely counterproductive. >> >> Two scenarios can arise while you test before you have fully polished: >> >> 1) Figure is very good. Result: You will feel tempted not to finish >> polishing in order not to spoil the good shape of the mirror. >> 2) Figure is defective. Result: Instead of concentrating on completely >> polishing, you will start corrections and eventually arrive at case 1) >> >> Both cases will leave you probably with a mirror that is not fully >> polished, >> which is why I would recommend not to test before your mirror is >> completely >> polished. The added benefit is that figuring after polishing gives you >> additional polishing time to really make sure you polished out all >> grayness. >> >> So I think you should just continue polishing. >> >> Berthold >> >> -- >> Berthold Hamburger - Cellist/Spain >> Email: behambu at artinso.com >> http://www.artinso.com >> http://www.astro.artinso.com >> >> >> > -----Original Message----- >> > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On >> > Behalf Of Brad Gilbert >> > Sent: s?bado, 11 de julio de 2009 9:18 >> > To: atm at atmlist.net >> > Subject: [ATM] Polishing First Mirror >> > >> > Hello, I am about 3-4 Hours into polishing my first mirror. >> > >> > The lines are very well defined and not jaggy or "doggybisuity". But, >> > theres a central hill and I have a 1/4" TDE. >> > >> > >> > Should I just finish polishing out or do something now to fix this? >> > _______________________________________________ >> > ATM mailing list http://www.atmlist.net/ >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> >> > From richard at foucault.co.uk Mon Jul 13 19:01:50 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Mon, 13 Jul 2009 11:01:50 +0100 Subject: [ATM] astigmatism tests In-Reply-To: References: Message-ID: <1478010099.20090713110150@foucault.co.uk> Hello Richard, Monday, July 13, 2009, 5:03:08 AM, you wrote: > I suggest that you glue the mirror to a stiff metal plate I disagree Richard. You can get very small diamond conterbore drills now, so I have found 6 holes round the edge and torquing it down with 3/8" cap heads much better. -- Best regards, Richard in the UK From robert.houdart at cruxis.be Mon Jul 13 20:57:00 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 13 Jul 2009 13:57:00 +0200 Subject: [ATM] astigmatism tests In-Reply-To: <398213C674F7554AB0F55401DF29FBD10139A756@ziggy.decatur-al.net> Message-ID: Tom, > Does the position of the roller bearings change when you > collimate the telescope? Depends. In the 16 inch on Jan's web site, the rollers are mounted on the mirror cell frame, so no. In the second example the rollers are attached to the mirror box, so yes. Night-time collimation usually requires mirror movements of less than a millimeter, so either solution works quite well in practice. Regards, Robert From robert.houdart at cruxis.be Mon Jul 13 21:17:05 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 13 Jul 2009 14:17:05 +0200 Subject: [ATM] astigmatism tests In-Reply-To: <734485.93509.qm@web112414.mail.gq1.yahoo.com> Message-ID: Mark, > I've no idea how you can get somebody to supply a consensus > on this. You're the third person to recommend the 90? pegs/rollers solution, it would seem that at least some consensus has been reached ;). Robert From stainless_steel at suddenlink.net Mon Jul 13 22:11:09 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 13 Jul 2009 08:11:09 -0500 Subject: [ATM] astigmatism tests In-Reply-To: <734485.93509.qm@web112414.mail.gq1.yahoo.com> References: <734485.93509.qm@web112414.mail.gq1.yahoo.com> Message-ID: Mark, all- When I visited the URL for your picture, my AVG security instantly gave me a warning that the file was infected with dangerous malware. It warned me that any attempt to repair the file, quarantine the file, etc.,, could result in a crash of the operating system, at worst. Just thought you ought to know what the latest version of AVG said about the picture, which is a very good one, making everything clear. D-LZ130 ----- Original Message ----- From: "Mark Cowan" To: "atm" ; "Jeff Baldwin" Sent: Monday, July 13, 2009 3:04 AM Subject: Re: [ATM] astigmatism tests > > I've no idea how you can get somebody to supply a consensus on this, but > FWIW I'll say that you're doing a couple things wrong supporting this 18:1 > mirror this way on the test stand. A lot of experimentation zeroed in on > the best test stand support for thin mirrors: > > 1) Lose the strap, use pegs where the pegs have a grommet or similar > fitting falling just outside the COG of the glass disk, oriented at 90 > degrees supporting the base of the glass. > > 2) No flexible back (carpet or cell), they don't do squat for vertical > testing. Produce a reasonably flat back support into which the pegs > insert in 90 degree holes, the support can be made of something like 1/2" > Corian countertop against a solid backer (this is what I'm using up to > 20"), whatever it is it must be quite flat and the back of the mirror > likewise. > > Then the mirror is just placed onto the backing and lowered into contact > with the grommets on the pegs gently, with no other pressure involved. > The large contact area of the back plus the small contact area on the pegs > easily counteracts the potato chipping you're seeing from the combo of > sling/carpet or sling/cell - I've seen this happen in experimenting with > supporting _full thick_ 12.5" Pyrex variously on a sling/foam/bubble > wrap... > > With proper support the mirror can't bend over because it's prevented from > this by the back support, and it can't bend forward at the base because > it's held by the contact points. Neither are true with slings and > flexible back supports. > > This setup allows me to easily verify lack of astigmatism in mirrors down > to about 20:1 aspect ratio, using a precision pinhole source and a 12mm EP > to view the resulting pattern through the caustic. > > Here's a picture of what I'm talking about with the pegs (I put some vinyl > hose behind the grommets to ensure alignment as needed): > > http://www.raddobs.com/atm/peg%20support.jpg > > Best, > Mark > > --- On Sat, 7/11/09, Jeff Baldwin wrote: > >> From: Jeff Baldwin >> Subject: [ATM] astigmatism tests >> To: "atm" >> Date: Saturday, July 11, 2009, 5:07 PM >> Hi ATMers: >> I am about 2 hours in to polishing a 24" f/3.6, the >> thickness at the edge is about 1.35". I am astigmatism >> testing before I continue. The mirror was mounted on two >> sheets of 3/4" plywood with a 1" strap contacting the mirror >> for about 140 degrees. Short pile carpet supports the mirror >> against the plywood. >> >> The vertical diameter has an ROC a bit longer than the >> horizontal diameter. I rotated the mirror 90 degrees, and >> again, the ROC is a bit longer on the vertical axis. Since >> the astigmatism did not rotate, my mirror holder is bending >> the glass. >> >> I then whipped up a 9-pt flotation cell for the mirror >> stand, and again, the vertical axis is a bit longer than the >> horizontal axis regardless of mirror orientation. So I >> eliminated the back support. I would like to confirm that I >> have no astigmatism in the glass. Seeing that my mount >> creates astigmatism does not mean that my mirror has none. >> But I need to elliminate this system error. >> >> I have heard urban legends regarding how many degrees the >> strap should contact the mirror, anywhere form 180 degrees, >> to 160 to 170, and many other ideas. I know that when I pose >> this question to the group I will get even more of these >> answers. Nonetheless, I am asking two questions. First, what >> is the concensus on degrees of contact for the strap, and >> second, how close to the front edge and back edge ought the >> strap stay back from. Meanwhile I am going to support the >> edge with about 170 degrees of contact and possibly use a >> thinner strap, and I will let you know what the results >> are. >> >> Thanks, will enjoy hearing from all of you. >> Bald >> >> Jeff and Glenda Baldwin >> Lathrop, CA >> www.stocktonastro.org >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.12/2235 - Release Date: 07/13/09 05:56:00 From stainless_steel at suddenlink.net Mon Jul 13 22:22:18 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 13 Jul 2009 08:22:18 -0500 Subject: [ATM] astigmatism tests In-Reply-To: <006901ca0390$c0ba01b0$422e0510$@com> References: <006901ca0390$c0ba01b0$422e0510$@com> Message-ID: Berthold, Do you think anyone remembers that clever tool for detecting astigmatism that was published in Albert Ingalls' three volume set on telescope making? I never had occasion to use it, because with the precautions I took (yes, I took precautions) I never, ever got astigmatism. Do you remember that cleverly designed little knife edge, with an included angle of 90 degrees, pointed upwards- it looked like an arrowhead. Never had occasion to try it, but it seemed very logically designed for its function. In the old Scientific American ATM books.. By the way, I got another warning from AVG about a harmful file, with your email. It gave me a long, rambling explanation about how much more prolific these worms are, and allowed me the option of putting it in the vault, after warning me that doing so could crash the computer. It said these harmful files are becoming much more prolific now, for one reason or other, and their spread is becoming much wider and easier-they are spreading faster than ever before. Computer did not crash. D-LZ130 ----- Original Message ----- From: "Berthold Hamburger" To: "'Richard Schwartz'" Cc: Sent: Monday, July 13, 2009 3:05 AM Subject: Re: [ATM] astigmatism tests > Richard, > > That reminds me of an advice you gave to an aspiring telescope maker some > 10-12 years ago about making a pitch lap. If I remember correctly, the > poor > lad was told to boil turpentine on the kitchen stove before mixing it with > pitch in order to make his first (and probably last) polishing lap. > Anyway, > I think he was told (just) in time that your suggestion was a hoax and > lives > happily ever since.... > > I guess no rescuer is needed presently, but maybe we could agree on a > secret > moniker to safely identify and separate hoax from true wisdom. After all, > all those messages end up in the archives and some poor guy might really > end > up cementing his glass to a metal backing one day, because he read your > message out of context. > > Berthold > > -- > Berthold Hamburger - Cellist/Spain > Email: behambu at artinso.com > http://www.artinso.com > http://www.astro.artinso.com > > >> -----Original Message----- >> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf >> Of Richard Schwartz >> Sent: lunes, 13 de julio de 2009 6:03 >> To: 'Jeff Baldwin'; 'atm' >> Subject: Re: [ATM] astigmatism tests >> >> I suggest that you glue the mirror to a stiff metal plate so that it can >> not >> flex. Just use a very thin layer of epoxy, and slide to mirror around a >> bit >> before the epoxy gets stiff. Be sure that the glue layer is thin and >> that >> there are no air bubbles in it behind the mirror. You will get better >> adhesion if the back of the mirror is fine ground on the same metal >> plate it >> is to be bonded to. Then you should add mirror clips around the edge, >> and >> make them really tight, for safety and to assure that nothing will >> rattle >> loose in there. >> >> -----Original Message----- >> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf >> Of >> Jeff Baldwin >> Sent: Saturday, July 11, 2009 5:07 PM >> To: atm >> Subject: [ATM] astigmatism tests >> >> >> Hi ATMers: >> I am about 2 hours in to polishing a 24" f/3.6, the thickness at the >> edge is >> about 1.35". I am astigmatism testing before I continue. The mirror was >> mounted on two sheets of 3/4" plywood with a 1" strap contacting the >> mirror >> for about 140 degrees. Short pile carpet supports the mirror against the >> plywood. >> >> The vertical diameter has an ROC a bit longer than the horizontal >> diameter. >> I rotated the mirror 90 degrees, and again, the ROC is a bit longer on >> the >> vertical axis. Since the astigmatism did not rotate, my mirror holder is >> bending the glass. >> >> I then whipped up a 9-pt flotation cell for the mirror stand, and again, >> the >> vertical axis is a bit longer than the horizontal axis regardless of >> mirror >> orientation. So I eliminated the back support. I would like to confirm >> that >> I have no astigmatism in the glass. Seeing that my mount creates >> astigmatism >> does not mean that my mirror has none. But I need to elliminate this >> system >> error. >> >> I have heard urban legends regarding how many degrees the strap should >> contact the mirror, anywhere form 180 degrees, to 160 to 170, and many >> other >> ideas. I know that when I pose this question to the group I will get >> even >> more of these answers. Nonetheless, I am asking two questions. First, >> what >> is the concensus on degrees of contact for the strap, and second, how >> close >> to the front edge and back edge ought the strap stay back from. >> Meanwhile I >> am going to support the edge with about 170 degrees of contact and >> possibly >> use a thinner strap, and I will let you know what the results are. >> >> Thanks, will enjoy hearing from all of you. >> Bald >> >> Jeff and Glenda Baldwin >> Lathrop, CA >> www.stocktonastro.org _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.12/2235 - Release Date: 07/13/09 05:56:00 From stainless_steel at suddenlink.net Mon Jul 13 22:27:17 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 13 Jul 2009 08:27:17 -0500 Subject: [ATM] astigmatism tests In-Reply-To: <1478010099.20090713110150@foucault.co.uk> References: <1478010099.20090713110150@foucault.co.uk> Message-ID: I glued a large diagonal once onto a metal plate; it prevented the mirror from adapting to the strain caused by temperature changes. It was a disaster- horrible astigmatism. In some literature somewhere, I later read a warning about this, not to glue any mirror across its back side to a plate. D-LZ130 ----- Original Message ----- From: "Richard in the UK" To: "Richard Schwartz" Sent: Monday, July 13, 2009 5:01 AM Subject: Re: [ATM] astigmatism tests > Hello Richard, > > Monday, July 13, 2009, 5:03:08 AM, you wrote: > >> I suggest that you glue the mirror to a stiff metal plate > > I disagree Richard. You can get very small diamond conterbore drills > now, so I have found 6 holes round the edge and torquing it down with > 3/8" cap heads much better. > > -- > Best regards, > Richard in the UK > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.12/2235 - Release Date: 07/13/09 05:56:00 From gfbrandenburg at yahoo.com Mon Jul 13 22:50:17 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Mon, 13 Jul 2009 06:50:17 -0700 (PDT) Subject: [ATM] astigmatism tests In-Reply-To: <734485.93509.qm@web112414.mail.gq1.yahoo.com> Message-ID: <830814.28857.qm@web111506.mail.gq1.yahoo.com> There is another approach. Don't put a thin mirror like this on a vertical stand at all! What I did for my (as yet unfinished) 16.5 inch mirror was to make a stand that sits on the floor. It has a 9-point floating support and a 180-degree strap. The tester is put on a slanted board at about chest level, so that when you are seated, you can see everything in comfort. This setup completely eliminated the astigmatism that I feared I was having. It was just potato-chipping due to the mirror being on edge. Think about it now: you essentially will NEVER use a telescope with the mirror in a vertical position. So why test the mirror in that position? Anybody interested in seeing photos of my (admittedly ugly) slanted tester? It's made out of wood with various blots, bits of aluminum, strapping from REI, and some felt furniture pads. Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Mon, 7/13/09, Mark Cowan wrote: > From: Mark Cowan > Subject: Re: [ATM] astigmatism tests > To: "atm" , "Jeff Baldwin" > Date: Monday, July 13, 2009, 4:04 AM > > I've no idea how you can get somebody to supply a consensus > on this, but FWIW I'll say that you're doing a couple things > wrong supporting this 18:1 mirror this way on the test > stand.? A lot of experimentation zeroed in on the best > test stand support for thin mirrors: > > 1) Lose the strap, use pegs where the pegs have a grommet > or similar fitting falling just outside the COG of the glass > disk, oriented at 90 degrees supporting the base of the > glass. > > 2) No flexible back (carpet or cell), they don't do squat > for vertical testing.? Produce a reasonably flat back > support into which the pegs insert in 90 degree holes, the > support can be made of something like 1/2" Corian countertop > against a solid backer (this is what I'm using up to 20"), > whatever it is it must be quite flat and the back of the > mirror likewise. > > Then the mirror is just placed onto the backing and lowered > into contact with the grommets on the pegs gently, with no > other pressure involved.? The large contact area of the > back plus the small contact area on the pegs easily > counteracts the potato chipping you're seeing from the combo > of sling/carpet or sling/cell - I've seen this happen in > experimenting with supporting _full thick_ 12.5" Pyrex > variously on a sling/foam/bubble wrap...? > > With proper support the mirror can't bend over because it's > prevented from this by the back support, and it can't bend > forward at the base because it's held by the contact > points.? Neither are true with slings and flexible back > supports. > > This setup allows me to easily verify lack of astigmatism > in mirrors down to about 20:1 aspect ratio, using a > precision pinhole source and a 12mm EP to view the resulting > pattern through the caustic. > > Here's a picture of what I'm talking about with the pegs (I > put some vinyl hose behind the grommets to ensure alignment > as needed): > > http://www.raddobs.com/atm/peg%20support.jpg > > Best, > Mark > > --- On Sat, 7/11/09, Jeff Baldwin > wrote: > > > From: Jeff Baldwin > > Subject: [ATM] astigmatism tests > > To: "atm" > > Date: Saturday, July 11, 2009, 5:07 PM > > Hi ATMers: > > I am about 2 hours in to polishing a 24" f/3.6, the > > thickness at the edge is about 1.35". I am > astigmatism > > testing before I continue. The mirror was mounted on > two > > sheets of 3/4" plywood with a 1" strap contacting the > mirror > > for about 140 degrees. Short pile carpet supports the > mirror > > against the plywood. > > > > The vertical diameter has an ROC a bit longer than > the > > horizontal diameter. I rotated the mirror 90 degrees, > and > > again, the ROC is a bit longer on the vertical axis. > Since > > the astigmatism did not rotate, my mirror holder is > bending > > the glass. > > > > I then whipped up a 9-pt flotation cell for the > mirror > > stand, and again, the vertical axis is a bit longer > than the > > horizontal axis regardless of mirror orientation. So > I > > eliminated the back support. I would like to confirm > that I > > have no astigmatism in the glass. Seeing that my > mount > > creates astigmatism does not mean that my mirror has > none. > > But I need to elliminate this system error. > > > > I have heard urban legends regarding how many degrees > the > > strap should contact the mirror, anywhere form 180 > degrees, > > to 160 to 170, and many other ideas. I know that when > I pose > > this question to the group I will get even more of > these > > answers. Nonetheless, I am asking two questions. > First, what > > is the concensus on degrees of contact for the strap, > and > > second, how close to the front edge and back edge > ought the > > strap stay back from. Meanwhile I am going to support > the > > edge with about 170 degrees of contact and possibly > use a > > thinner strap, and I will let you know what the > results > > are. > > > > Thanks, will enjoy hearing from all of you. > > Bald > > > > Jeff and Glenda Baldwin > > Lathrop, CA > > www.stocktonastro.org > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > > > > ? ? ? > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From b-hamburger at artinso.com Mon Jul 13 22:56:32 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Mon, 13 Jul 2009 15:56:32 +0200 Subject: [ATM] astigmatism tests In-Reply-To: References: <006901ca0390$c0ba01b0$422e0510$@com> Message-ID: <008701ca03c1$bbaab9e0$33002da0$@com> Hi David, I will dig out my Ingalls books and check. For the AVG issue, my Eset smartsecurity could not find any fault with the link and I cannot remember sending a file with my mail. So I am a bit at a loss here. My system is also quite well protected and frequently scanned, so I would be surprised to have a problem locally. Also, as far as I remember the ATM list does not forward attachments, so it looks as if you might have a problem on your PC? All the best Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: stainless_steel at suddenlink.net > [mailto:stainless_steel at suddenlink.net] > Sent: lunes, 13 de julio de 2009 15:22 > To: ATM list; Berthold Hamburger > Subject: Re: [ATM] astigmatism tests > > Berthold, > > Do you think anyone remembers that clever tool for detecting astigmatism > that was published in Albert Ingalls' three volume set on telescope > making? > I never had occasion to use it, because with the precautions I took > (yes, I > took precautions) I never, ever got astigmatism. Do you remember that > cleverly designed little knife edge, with an included angle of 90 > degrees, > pointed upwards- it looked like an arrowhead. Never had occasion to try > it, > but it seemed very logically designed for its function. > > In the old Scientific American ATM books.. > > By the way, I got another warning from AVG about a harmful file, with > your > email. It gave me a long, rambling explanation about how much more > prolific > these worms are, and allowed me the option of putting it in the vault, > after > warning me that doing so could crash the computer. It said these harmful > files are becoming much more prolific now, for one reason or other, and > their spread is becoming much wider and easier-they are spreading faster > than ever before. > > > Computer did not crash. > > D-LZ130 > > > ----- Original Message ----- > From: "Berthold Hamburger" > To: "'Richard Schwartz'" > Cc: > Sent: Monday, July 13, 2009 3:05 AM > Subject: Re: [ATM] astigmatism tests > > > > Richard, > > > > That reminds me of an advice you gave to an aspiring telescope maker > some > > 10-12 years ago about making a pitch lap. If I remember correctly, the > > poor > > lad was told to boil turpentine on the kitchen stove before mixing it > with > > pitch in order to make his first (and probably last) polishing lap. > > Anyway, > > I think he was told (just) in time that your suggestion was a hoax and > > lives > > happily ever since.... > > > > I guess no rescuer is needed presently, but maybe we could agree on a > > secret > > moniker to safely identify and separate hoax from true wisdom. After > all, > > all those messages end up in the archives and some poor guy might > really > > end > > up cementing his glass to a metal backing one day, because he read > your > > message out of context. > > > > Berthold > > > > -- > > Berthold Hamburger - Cellist/Spain > > Email: behambu at artinso.com > > http://www.artinso.com > > http://www.astro.artinso.com > > > > > >> -----Original Message----- > >> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On > Behalf > >> Of Richard Schwartz > >> Sent: lunes, 13 de julio de 2009 6:03 > >> To: 'Jeff Baldwin'; 'atm' > >> Subject: Re: [ATM] astigmatism tests > >> > >> I suggest that you glue the mirror to a stiff metal plate so that it > can > >> not > >> flex. Just use a very thin layer of epoxy, and slide to mirror > around a > >> bit > >> before the epoxy gets stiff. Be sure that the glue layer is thin and > >> that > >> there are no air bubbles in it behind the mirror. You will get > better > >> adhesion if the back of the mirror is fine ground on the same metal > >> plate it > >> is to be bonded to. Then you should add mirror clips around the > edge, > >> and > >> make them really tight, for safety and to assure that nothing will > >> rattle > >> loose in there. > >> > >> -----Original Message----- > >> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On > Behalf > >> Of > >> Jeff Baldwin > >> Sent: Saturday, July 11, 2009 5:07 PM > >> To: atm > >> Subject: [ATM] astigmatism tests > >> > >> > >> Hi ATMers: > >> I am about 2 hours in to polishing a 24" f/3.6, the thickness at the > >> edge is > >> about 1.35". I am astigmatism testing before I continue. The mirror > was > >> mounted on two sheets of 3/4" plywood with a 1" strap contacting the > >> mirror > >> for about 140 degrees. Short pile carpet supports the mirror against > the > >> plywood. > >> > >> The vertical diameter has an ROC a bit longer than the horizontal > >> diameter. > >> I rotated the mirror 90 degrees, and again, the ROC is a bit longer > on > >> the > >> vertical axis. Since the astigmatism did not rotate, my mirror holder > is > >> bending the glass. > >> > >> I then whipped up a 9-pt flotation cell for the mirror stand, and > again, > >> the > >> vertical axis is a bit longer than the horizontal axis regardless of > >> mirror > >> orientation. So I eliminated the back support. I would like to > confirm > >> that > >> I have no astigmatism in the glass. Seeing that my mount creates > >> astigmatism > >> does not mean that my mirror has none. But I need to elliminate this > >> system > >> error. > >> > >> I have heard urban legends regarding how many degrees the strap > should > >> contact the mirror, anywhere form 180 degrees, to 160 to 170, and > many > >> other > >> ideas. I know that when I pose this question to the group I will get > >> even > >> more of these answers. Nonetheless, I am asking two questions. First, > >> what > >> is the concensus on degrees of contact for the strap, and second, how > >> close > >> to the front edge and back edge ought the strap stay back from. > >> Meanwhile I > >> am going to support the edge with about 170 degrees of contact and > >> possibly > >> use a thinner strap, and I will let you know what the results are. > >> > >> Thanks, will enjoy hearing from all of you. > >> Bald > >> > >> Jeff and Glenda Baldwin > >> Lathrop, CA > >> www.stocktonastro.org _______________________________________________ > >> ATM mailing list http://www.atmlist.net/ > >> > >> _______________________________________________ > >> ATM mailing list http://www.atmlist.net/ > > > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > > ------------------------------------------------------------------------ > -------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.375 / Virus Database: 270.13.12/2235 - Release Date: > 07/13/09 > 05:56:00 From b-hamburger at artinso.com Mon Jul 13 23:00:08 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Mon, 13 Jul 2009 16:00:08 +0200 Subject: [ATM] astigmatism tests In-Reply-To: <830814.28857.qm@web111506.mail.gq1.yahoo.com> References: <734485.93509.qm@web112414.mail.gq1.yahoo.com> <830814.28857.qm@web111506.mail.gq1.yahoo.com> Message-ID: <008801ca03c2$3d36c9e0$b7a45da0$@com> Just out of interest: How are 1m+ mirrors tested? I guess slings are not an issue there anymore? Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Guy Brandenburg > Sent: lunes, 13 de julio de 2009 15:50 > To: atm; Jeff Baldwin; Mark Cowan > Subject: Re: [ATM] astigmatism tests > > > There is another approach. Don't put a thin mirror like this on a > vertical stand at all! What I did for my (as yet unfinished) 16.5 inch > mirror was to make a stand that sits on the floor. It has a 9-point > floating support and a 180-degree strap. The tester is put on a slanted > board at about chest level, so that when you are seated, you can see > everything in comfort. > This setup completely eliminated the astigmatism that I feared I was > having. It was just potato-chipping due to the mirror being on edge. > > Think about it now: you essentially will NEVER use a telescope with the > mirror in a vertical position. So why test the mirror in that position? > > Anybody interested in seeing photos of my (admittedly ugly) slanted > tester? It's made out of wood with various blots, bits of aluminum, > strapping from REI, and some felt furniture pads. > > Guy Brandenburg, Washington, DC > My home page on astronomy, mathematics, education: > http://home.earthlink.net/~gfbranden/GFB_Home_Page.html > or else > http://tinyurl.com/r6fh2 > > ============================= > "Education isn't rocket science. It's much, much harder." > (Author unknown) > > > > --- On Mon, 7/13/09, Mark Cowan wrote: > > > From: Mark Cowan > > Subject: Re: [ATM] astigmatism tests > > To: "atm" , "Jeff Baldwin" > > Date: Monday, July 13, 2009, 4:04 AM > > > > I've no idea how you can get somebody to supply a consensus > > on this, but FWIW I'll say that you're doing a couple things > > wrong supporting this 18:1 mirror this way on the test > > stand.? A lot of experimentation zeroed in on the best > > test stand support for thin mirrors: > > > > 1) Lose the strap, use pegs where the pegs have a grommet > > or similar fitting falling just outside the COG of the glass > > disk, oriented at 90 degrees supporting the base of the > > glass. > > > > 2) No flexible back (carpet or cell), they don't do squat > > for vertical testing.? Produce a reasonably flat back > > support into which the pegs insert in 90 degree holes, the > > support can be made of something like 1/2" Corian countertop > > against a solid backer (this is what I'm using up to 20"), > > whatever it is it must be quite flat and the back of the > > mirror likewise. > > > > Then the mirror is just placed onto the backing and lowered > > into contact with the grommets on the pegs gently, with no > > other pressure involved.? The large contact area of the > > back plus the small contact area on the pegs easily > > counteracts the potato chipping you're seeing from the combo > > of sling/carpet or sling/cell - I've seen this happen in > > experimenting with supporting _full thick_ 12.5" Pyrex > > variously on a sling/foam/bubble wrap... > > > > With proper support the mirror can't bend over because it's > > prevented from this by the back support, and it can't bend > > forward at the base because it's held by the contact > > points.? Neither are true with slings and flexible back > > supports. > > > > This setup allows me to easily verify lack of astigmatism > > in mirrors down to about 20:1 aspect ratio, using a > > precision pinhole source and a 12mm EP to view the resulting > > pattern through the caustic. > > > > Here's a picture of what I'm talking about with the pegs (I > > put some vinyl hose behind the grommets to ensure alignment > > as needed): > > > > http://www.raddobs.com/atm/peg%20support.jpg > > > > Best, > > Mark > > > > --- On Sat, 7/11/09, Jeff Baldwin > > wrote: > > > > > From: Jeff Baldwin > > > Subject: [ATM] astigmatism tests > > > To: "atm" > > > Date: Saturday, July 11, 2009, 5:07 PM > > > Hi ATMers: > > > I am about 2 hours in to polishing a 24" f/3.6, the > > > thickness at the edge is about 1.35". I am > > astigmatism > > > testing before I continue. The mirror was mounted on > > two > > > sheets of 3/4" plywood with a 1" strap contacting the > > mirror > > > for about 140 degrees. Short pile carpet supports the > > mirror > > > against the plywood. > > > > > > The vertical diameter has an ROC a bit longer than > > the > > > horizontal diameter. I rotated the mirror 90 degrees, > > and > > > again, the ROC is a bit longer on the vertical axis. > > Since > > > the astigmatism did not rotate, my mirror holder is > > bending > > > the glass. > > > > > > I then whipped up a 9-pt flotation cell for the > > mirror > > > stand, and again, the vertical axis is a bit longer > > than the > > > horizontal axis regardless of mirror orientation. So > > I > > > eliminated the back support. I would like to confirm > > that I > > > have no astigmatism in the glass. Seeing that my > > mount > > > creates astigmatism does not mean that my mirror has > > none. > > > But I need to elliminate this system error. > > > > > > I have heard urban legends regarding how many degrees > > the > > > strap should contact the mirror, anywhere form 180 > > degrees, > > > to 160 to 170, and many other ideas. I know that when > > I pose > > > this question to the group I will get even more of > > these > > > answers. Nonetheless, I am asking two questions. > > First, what > > > is the concensus on degrees of contact for the strap, > > and > > > second, how close to the front edge and back edge > > ought the > > > strap stay back from. Meanwhile I am going to support > > the > > > edge with about 170 degrees of contact and possibly > > use a > > > thinner strap, and I will let you know what the > > results > > > are. > > > > > > Thanks, will enjoy hearing from all of you. > > > Bald > > > > > > Jeff and Glenda Baldwin > > > Lathrop, CA > > > www.stocktonastro.org > > > _______________________________________________ > > > ATM mailing list http://www.atmlist.net/ > > > > > > > > > > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From robert.houdart at cruxis.be Mon Jul 13 23:16:15 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 13 Jul 2009 16:16:15 +0200 Subject: [ATM] astigmatism tests In-Reply-To: <830814.28857.qm@web111506.mail.gq1.yahoo.com> Message-ID: Guy, > Think about it now: you essentially will NEVER use a > telescope with the mirror in a vertical position. So why > test the mirror in that position? Because even as high as 45? altitude you still have 70% of the load on the edge support, so you'll still find 70% of astigmatism. This year I'm observing Jupiter at altitudes mostly between 20? and 25?, in that situation the edge support carries 90% of its nominal load. Robert http://www.cruxis.com/scope/scope1100.htm From richard at foucault.co.uk Tue Jul 14 01:22:02 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Mon, 13 Jul 2009 17:22:02 +0100 Subject: [ATM] astigmatism tests In-Reply-To: <830814.28857.qm@web111506.mail.gq1.yahoo.com> References: <734485.93509.qm@web112414.mail.gq1.yahoo.com> <830814.28857.qm@web111506.mail.gq1.yahoo.com> Message-ID: <17810176817.20090713172202@foucault.co.uk> Hello Guy, Monday, July 13, 2009, 2:50:17 PM, you wrote: > There is another approach. Don't put a thin mirror like this on a > vertical stand at all! Agreed. Interferometer sitting on slides through the ceiling into the loft works well. -- Best regards, Richard in the UK From ericandroberta at sbcglobal.net Tue Jul 14 01:57:45 2009 From: ericandroberta at sbcglobal.net (D ERIC ALLEN) Date: Mon, 13 Jul 2009 09:57:45 -0700 (PDT) Subject: [ATM] unequal tool and mirror blank Message-ID: <249428.79496.qm@web80505.mail.mud.yahoo.com> Is there any problem with grinding a six-inch blank against a five-inch blank?? This is for my cass secondary, so I'll be making the secondary out of the five incher and the test plate out of the six inch.? I will probably make plaster tools for polishing and figuring, but was hoping to be able to grind the blanks against each other.? Will this work?? Anything special I need to do?? Can I do both?5" on top and?6" on top? Thanks Eric From mjc5 at psu.edu Tue Jul 14 02:52:15 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 13 Jul 2009 13:52:15 -0400 Subject: [ATM] astigmatism tests In-Reply-To: References: Message-ID: On Jul 13, 2009, at 12:03 AM, Richard Schwartz wrote: > I suggest that you glue the mirror to a stiff metal plate so that it > can not > flex. Just use a very thin layer of epoxy, and slide to mirror > around a bit > before the epoxy gets stiff. Be sure that the glue layer is thin and > that > there are no air bubbles in it behind the mirror. You will get better > adhesion if the back of the mirror is fine ground on the same metal > plate it > is to be bonded to. Then you should add mirror clips around the > edge, and > make them really tight, for safety and to assure that nothing will > rattle > loose in there. Hardly secure enough Richard. I personally drill and tap 12 1/4-20 holes in the back of my mirror (real men use only full thickness blanks) and bolt the mirror onto the mirror cell. You've never lived until you've successfully run a tap through glass. -73 de Mike N3LI - From mjc5 at psu.edu Tue Jul 14 02:59:21 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 13 Jul 2009 13:59:21 -0400 Subject: [ATM] astigmatism tests In-Reply-To: <006901ca0390$c0ba01b0$422e0510$@com> References: <006901ca0390$c0ba01b0$422e0510$@com> Message-ID: <0D87A965-41F8-4C54-86FA-C0DD37EA4499@psu.edu> On Jul 13, 2009, at 4:05 AM, Berthold Hamburger wrote: > > I guess no rescuer is needed presently, but maybe we could agree on > a secret > moniker to safely identify and separate hoax from true wisdom. After > all, > all those messages end up in the archives and some poor guy might > really end > up cementing his glass to a metal backing one day, because he read > your > message out of context. Hoo boy, I'll probably catch it with my bolted mirror post then........ Of course mine suggestion was patently ridiculous, I'm nowhere near the level of the master of leg pulling that Richard is. He can make it sound like the *exact* thing to do. -73 de Mike N3LI - From mjc5 at psu.edu Tue Jul 14 03:15:36 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 13 Jul 2009 14:15:36 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907130137p1f0fcdffl75caab2033e08230@mail.gmail.com> References: <008201ca01fc$b0e2cb40$12a861c0$@com> <42ee1e6c0907122149y3f255edcpbb7ef47fa05d0e3f@mail.gmail.com> <42ee1e6c0907130137p1f0fcdffl75caab2033e08230@mail.gmail.com> Message-ID: <1A260D02-D1CD-4565-B293-F25A91F73A36@psu.edu> On Jul 13, 2009, at 4:37 AM, Brad Gilbert wrote: > I made some great progress today! > > After several failure 2+ sessions which saw no progress, I decided > to take > action and modify my pitch lap. I made the channels much deeper with a > triangle ruler and a blow drier. This led to contact being terrible > so I > warm pressed with this cloth mesh I found for an hour or two. > > The texture makes such a big difference, it's insane! I had about a > 60% pit > reduction in the center in one 15 minute session. Compared to like > 0% for 4 > hours this is great. Isn't microfaceting great? Keep going.... > There is still contact issues as the center is having some sphere in a > sphere sorta thing going on. I'm warm pressing right now again with > more > weight so we'll see where that gets me. Be careful not to indent the cloth so deep that it pulls pitch out of the tool when you remove it. That gets kind of messy. It is interesting that your having contact issues with that very soft pitch. Just to be sure, are you seeing this in the testing, or by eyeball? Sphere in a sphere sounds almost like something you might actually want to see at some point. But don't pay attention to that, get your mirror spherical first. Some folks like to talk about going directly to the parabola. I think that is an advanced technique, and until a person learns to get to a sphere, then parabolize, they will be better served. There is a lot of getting the process under control that is needed before one is ready to go for the parabola on one shot. It sounds like you are doing very well. Just keep polishing and try not to worry too much about what you are seeing in your initial tests. If you don't see gross problems like astig, or some mountainous doodad in the tests, you're on your way. -73 de Mike N3LI - From b-hamburger at artinso.com Tue Jul 14 04:12:43 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Mon, 13 Jul 2009 21:12:43 +0200 Subject: [ATM] astigmatism tests In-Reply-To: <0D87A965-41F8-4C54-86FA-C0DD37EA4499@psu.edu> References: <006901ca0390$c0ba01b0$422e0510$@com> <0D87A965-41F8-4C54-86FA-C0DD37EA4499@psu.edu> Message-ID: <00c001ca03ed$e73c4660$b5b4d320$@com> You guys are all Schwarz-listed already ;-) I am trying to imagine some kind of Ingall 40 years from now compiling half a century worth of telescope making wisdom in a 5 volume 3000 page masterpiece with special chapters devoted to exotic techniques like boiling turpentine in pressure cookers, tapping threads in full thickness blanks, ... Which makes me wonder whether some of Richards ancestors might have contributed already to our standard literature... Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Michael Coslo > Sent: lunes, 13 de julio de 2009 19:59 > To: ATM List > Subject: Re: [ATM] astigmatism tests > > > On Jul 13, 2009, at 4:05 AM, Berthold Hamburger wrote: > > > > I guess no rescuer is needed presently, but maybe we could agree on > > a secret > > moniker to safely identify and separate hoax from true wisdom. After > > all, > > all those messages end up in the archives and some poor guy might > > really end > > up cementing his glass to a metal backing one day, because he read > > your > > message out of context. > > > Hoo boy, I'll probably catch it with my bolted mirror post then........ > > Of course mine suggestion was patently ridiculous, I'm nowhere near > the level of the master of leg pulling that Richard is. He can make it > sound like the *exact* thing to do. > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From toolontop at yahoo.com Tue Jul 14 04:17:59 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Mon, 13 Jul 2009 12:17:59 -0700 (PDT) Subject: [ATM] astigmatism tests In-Reply-To: Message-ID: <817521.86474.qm@web112406.mail.gq1.yahoo.com> How curious. It ain't me - I run up-to-date AVG 8.5.339 with no infected files on this computer, and the file isn't new. Could this be another case of loose mirror clips?? ;) Best, Mark --- On Mon, 7/13/09, stainless_steel at suddenlink.net wrote: > From: stainless_steel at suddenlink.net > Subject: Re: [ATM] astigmatism tests > To: "Mark Cowan" , "atm" , "Jeff Baldwin" > Date: Monday, July 13, 2009, 6:11 AM > Mark, all- > > When I visited the URL for your picture, my AVG security > instantly gave me a warning that the file was infected with > dangerous malware. It warned me that any attempt to repair > the file, quarantine the file, etc.,, could result in a > crash of the operating system, at worst. Just thought you > ought to know what the latest version of AVG said about the > picture, which is a very good one, making everything clear. > > D-LZ130 > > From toolontop at yahoo.com Tue Jul 14 04:29:58 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Mon, 13 Jul 2009 12:29:58 -0700 (PDT) Subject: [ATM] astigmatism tests In-Reply-To: Message-ID: <723102.63867.qm@web112405.mail.gq1.yahoo.com> What do you use to lubricate the tap, though? Mark --- On Mon, 7/13/09, Michael Coslo wrote: > From: Michael Coslo > Subject: Re: [ATM] astigmatism tests > To: "Richard Schwartz" > Cc: "ATM List" > Date: Monday, July 13, 2009, 10:52 AM > > On Jul 13, 2009, at 12:03 AM, Richard Schwartz wrote: > > > I suggest that you glue the mirror to a stiff metal > plate so that it can not > > flex.? Just use a very thin layer of epoxy, and > slide to mirror around a bit > > before the epoxy gets stiff. Be sure that the glue > layer is thin and that > > there are no air bubbles in it behind the > mirror.? You will get better > > adhesion if the back of the mirror is fine ground on > the same metal plate it > > is to be bonded to.? Then you should add mirror > clips around the edge, and > > make them really tight, for safety and to assure that > nothing will rattle > > loose in there. > > > Hardly secure enough Richard. I personally drill and tap 12 > 1/4-20 holes in the back of my mirror (real men use only > full thickness blanks) and bolt the mirror onto the mirror > cell. You've never lived until you've successfully run a tap > through glass. > > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From baldjeff at comcast.net Tue Jul 14 04:36:48 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Mon, 13 Jul 2009 12:36:48 -0700 Subject: [ATM] astigmatism update Message-ID: <7DDD0BB48E8B4BD698C578C270A5E2F4@glendaspc> Hi gang; I'm the one who posted the original issue. Here's my update. I've tried a carpetted plywood with a sling at 140 degress, I moved the sling to 180 degrees, I've replaced the carpet with a 9-point flotation I derived off of PLOP, I've replaced the sling with a wire (180 degrees), and I've replaced the wire with two pegs at 90 degrees. I still have a longer ROC for the vertical diameter than for the horizontal diameter. Furthermore, I would have expected the mirror to relax vertically producing a shorter ROC on the vertical diameter than for the horizontal diameter, which is NOT the case. This must mean that the mirror is falling back, not leaning forward. My next trial will be with a formica style countertop board behind with two pegs, but I'm also thinking that the mirror will seek out 3 primary points of force against it. But I'm willing to try it. How, then, would I deal with this in my telescope??? I'm not going to put formica countertop in my telescope, I hope. Thanks to all who have tossed in on this, both serious and silly. After 300 mirrors, I'm not a total newbie, but am perplexed by this particular project. This can't be entirely that the mirror is too thin, many of you guys have been doing mirrors with higher aspect ratios than my 18:1 and have done so without the test stand destroying your information. Thanks again everybody. Bald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org From rmay at nethere.com Tue Jul 14 05:04:34 2009 From: rmay at nethere.com (Bob May) Date: Mon, 13 Jul 2009 13:04:34 -0700 Subject: [ATM] astigmatism tests References: <734485.93509.qm@web112414.mail.gq1.yahoo.com> Message-ID: <001e01ca03f5$257b7840$c7fe1345@amd> There is no HTML code with that address. It is a photo (.JPG) address and the AVG must be rejecting the file as it isn't HTML code. I haven't ppulled the file apart to find out if the header is munged up in some way but there should be no browser that should do anything with that file othter than display it as an image. I will note that the spec for .JPG images does have a variable space for adding in comments, etc. BUT that space is for documentation that should not be executed so there should be no problems there. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Tue Jul 14 05:12:10 2009 From: rmay at nethere.com (Bob May) Date: Mon, 13 Jul 2009 13:12:10 -0700 Subject: [ATM] unequal tool and mirror blank References: <249428.79496.qm@web80505.mail.mud.yahoo.com> Message-ID: <003901ca03f6$34bfbea0$c7fe1345@amd> No problem at all. If the convex is the 5" blank, you will have possibly a turned down edge if you don't grind over far enough on the 6" tool. This will result in a turned up shape to the sphere you are looking for at the beginning. That will just result in additional material you need to polish off. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From jack.swaton at starryhost.com Tue Jul 14 05:17:52 2009 From: jack.swaton at starryhost.com (Jack Swaton @ Starry Host) Date: Mon, 13 Jul 2009 13:17:52 -0700 Subject: [ATM] Destination of Completed Projects In-Reply-To: <7DDD0BB48E8B4BD698C578C270A5E2F4@glendaspc> References: <7DDD0BB48E8B4BD698C578C270A5E2F4@glendaspc> Message-ID: <0A5D2E3247FF47DAB4E2AAC31E33ACEC@MRBNOTEBOOK> I was just blown away by the number Jeff Baldwin tossed out in a post indicating he's not a newbie with 300 mirrors. That seems like so many to me it just floors me. Yet I'm sure others have that many as well and a number of telescopes you've completed too. So my silly question is, what do you folks do with all those completed telescopes and mirrors? I can't even imagine getting that many mirrors coated with prices as they are not to mention materials for the scopes and spiders and cells and... Just a point of respectful and fascinated curiosity, Jack www.StarryHost.com From jack.swaton at starryhost.com Tue Jul 14 05:28:26 2009 From: jack.swaton at starryhost.com (Jack Swaton @ Starry Host) Date: Mon, 13 Jul 2009 13:28:26 -0700 Subject: [ATM] Does Collimation change where the scope points Message-ID: Here's a question for you all: "Does collimation change where your scope points?" I have completed a tandem 13" newt project (using old Coulters). As I get the two tubes to point at the same object so I can view at the same time a 2nd observer is viewing, does changing the collimation of either tube change where that tube is pointing? I am having difficulty testing this in the field because of confounding factors (such as mount stability, ability to see a fixed object such as the North Star, etc). Just thought you might have a good theory and two cents. Thanks, Jack Swaton www.StarryHost.com From mjc5 at psu.edu Tue Jul 14 02:17:57 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 13 Jul 2009 13:17:57 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <4A58C1A1.4070708@outofoptions.org> References: <42ee1e6c0907110018k766c84efj410172b069b91972@mail.gmail.com> <008201ca01fc$b0e2cb40$12a861c0$@com> <4A589F06.3060108@outofoptions.org> <001501ca0240$87e27c10$97a77430$@com> <4A58C1A1.4070708@outofoptions.org> Message-ID: On Jul 11, 2009, at 12:45 PM, hermit wrote: > Berthold Hamburger wrote: >> Hi Ken, >> >> Obviously there are many ways that lead to good mirrors. The >> question to ask >> is, why would you test the figure of an unpolished mirror if not >> for saving >> time and correcting while polishing? Otherwise there is little >> point in >> testing, I'd say. >> >> > > The point isn't to test the figure though. It is a check on your > technique and a look at how the glass is holding a shape. It will > tell you if you polished close to a sphere. Bad stig will show. > And who polishing a first mirror is going to wait until the polish > is done to take a look at a Ronchi or Foucault? ;) > Must......resist..........checking......... agggggh! You're right Ken, it's just too irresistible, so yeah, Brad, you did it. Now the big thing is to not get too carried away by what you see, especially if as Berthold notes, it seems to have a good figure before it is actually polished out. This stage is where you mess about with the tests, just play and have a good time. The sweatwork will come later. I'm a little concerned about the TDE. Are you sure you have it? I'm assuming that you are also doing your first mirror tests along with your first mirror? If you plan on getting rid of it, you'll have quite a bit of work removing the excess glass. That happened to me, but the consolation is that when you get rid of the turned edge, you *will* have a good polish. -73 de Mike N3LI - From anishmangal2002 at gmail.com Tue Jul 14 05:47:38 2009 From: anishmangal2002 at gmail.com (Anish Mangal) Date: Tue, 14 Jul 2009 02:17:38 +0530 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: References: Message-ID: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> Theoretically it should change... During collimation, assuming that you are also adjusting the primary, changing the alignment of the primary will change where it is pointing to (but not by a very big deal). Ideally the primary mirror should be aligned to the telescope's truss/tube for a well collimated scope, otherwise it may cause vignetting. After collimation, you'll also need to realign the finder-scope with the telescope. Anish New Delhi, India On Tue, Jul 14, 2009 at 1:58 AM, Jack Swaton @ Starry Host < jack.swaton at starryhost.com> wrote: > Here's a question for you all: > > > > "Does collimation change where your scope points?" > > > > I have completed a tandem 13" newt project (using old Coulters). As I get > the two tubes to point at the same object so I can view at the same time a > 2nd observer is viewing, does changing the collimation of either tube > change > where that tube is pointing? > > > > I am having difficulty testing this in the field because of confounding > factors (such as mount stability, ability to see a fixed object such as the > North Star, etc). Just thought you might have a good theory and two cents. > > > > Thanks, > > Jack Swaton > > www.StarryHost.com > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mjc5 at psu.edu Tue Jul 14 05:55:54 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 13 Jul 2009 16:55:54 -0400 Subject: [ATM] astigmatism tests In-Reply-To: <00c001ca03ed$e73c4660$b5b4d320$@com> References: <006901ca0390$c0ba01b0$422e0510$@com> <0D87A965-41F8-4C54-86FA-C0DD37EA4499@psu.edu> <00c001ca03ed$e73c4660$b5b4d320$@com> Message-ID: <504EE252-27AC-406F-8BDF-3F18877C2EC6@psu.edu> On Jul 13, 2009, at 3:12 PM, Berthold Hamburger wrote: > > Which makes me wonder whether some of Richards ancestors might have > contributed already to our standard literature... Oh, snap! -73 de Mike N3LI - From mjc5 at psu.edu Tue Jul 14 05:56:32 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 13 Jul 2009 16:56:32 -0400 Subject: [ATM] astigmatism tests In-Reply-To: <723102.63867.qm@web112405.mail.gq1.yahoo.com> References: <723102.63867.qm@web112405.mail.gq1.yahoo.com> Message-ID: <6A30CDA3-31D2-4857-82EC-A479F68ED36B@psu.edu> On Jul 13, 2009, at 3:29 PM, Mark Cowan wrote: > > What do you use to lubricate the tap, though? > Tears.. -73 de Mike N3LI - From robert.houdart at cruxis.be Tue Jul 14 06:08:15 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 13 Jul 2009 23:08:15 +0200 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: Message-ID: Jack, > "Does collimation change where your scope points?" Yes, it does, as can be observed quite easily in a telescope. Robert From richard at foucault.co.uk Tue Jul 14 06:11:01 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Mon, 13 Jul 2009 22:11:01 +0100 Subject: [ATM] astigmatism tests In-Reply-To: <723102.63867.qm@web112405.mail.gq1.yahoo.com> References: <723102.63867.qm@web112405.mail.gq1.yahoo.com> Message-ID: <446098040.20090713221101@foucault.co.uk> Hello Mark, Monday, July 13, 2009, 8:29:58 PM, you wrote: > What do you use to lubricate the tap, though? Ultrasound. No, really... -- Best regards, Richard in the UK From gary at gfphoto.com Tue Jul 14 06:19:08 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Mon, 13 Jul 2009 17:19:08 -0400 Subject: [ATM] Polishing First Mirror Message-ID: <4A5BA4CC.9090806@gfphoto.com> "I think that testing the mirror before it is fully polished is not only not helpful, but completely counterproductive. Two scenarios can arise while you test before you have fully polished: 1) Figure is very good. Result: You will feel tempted not to finish polishing in order not to spoil the good shape of the mirror. 2) Figure is defective. Result: Instead of concentrating on completely polishing, you will start corrections and eventually arrive at case 1) Both cases will leave you probably with a mirror that is not fully polished, which is why I would recommend not to test before your mirror is completely, polished. The added benefit is that figuring after polishing gives you additional polishing time to really make sure you polished out all grayness. So I think you should just continue polishing. Berthold" With due respect, I don't agree with the attitude of the above. I object to the notion that we should be prevented from knowing things: by our betters and for our own good - because we may be too weak to avoid certain temptations our betters wouldn't (or did?) succumb to. "You will feel tempted not to finish polishing in order not to spoil the good shape of the mirror." Is this something you know about this person in particular, or the general rule it appears to be? I think it's just as likely that one would be encouraged to continue to a full polish by good test results. Or, if there was a problem, be encouraged to take corrective action along the way. Gary Fuchs From gfbrandenburg at yahoo.com Tue Jul 14 06:54:03 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Mon, 13 Jul 2009 14:54:03 -0700 (PDT) Subject: [ATM] Polishing First Mirror In-Reply-To: Message-ID: <215166.66078.qm@web111511.mail.gq1.yahoo.com> If you are helping someone who is a first-timer, I think that having them take a look at their mirror as soon as it is possible to do so is not a bad thing but something that will encourage them to keep going. It also allows them to get a better sense of what their focal length really is, in case they are trying to make the mirror and the rest of the scope at the same time. Yes, there is temptation to stop using plain old polishing strokes (which I would define as mostly 1/3 nearly-but-not-completely COC with lots of systematically random rotation of tool and mirror) and to begin trying to work on other problems. Just resist that temptation, and keep polishing until it is really and truly polished. Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Mon, 7/13/09, Michael Coslo wrote: > From: Michael Coslo > Subject: Re: [ATM] Polishing First Mirror > To: "ATM List" > Date: Monday, July 13, 2009, 1:17 PM > > On Jul 11, 2009, at 12:45 PM, hermit wrote: > > > Berthold Hamburger wrote: > >> Hi Ken, > >> > >> Obviously there are many ways that lead to good > mirrors. The question to ask > >> is, why would you test the figure of an unpolished > mirror if not for saving > >> time and correcting while polishing? Otherwise > there is little point in > >> testing, I'd say. > >> > >> > > > > The point isn't to test the figure though.? It is > a check on your technique and a look at how the glass is > holding a shape.? It will tell you if you polished > close to a sphere.? Bad stig will show. > > And who polishing a first mirror is going to wait > until the polish is done to take a look at a Ronchi or > Foucault? ;) > > > > Must......resist..........checking......... agggggh! > > You're right Ken, it's just too irresistible, so yeah, > Brad, you did it. Now the big thing is to not get too > carried away by what you see, especially if as Berthold > notes, it seems to have a good figure before it is actually > polished out. > > This stage is where you mess about with the tests, just > play and have a good time. The sweatwork will come later. > > I'm a little concerned about the TDE. Are you sure you have > it? I'm assuming that you are also doing your first mirror > tests along with your first mirror? If you plan on getting > rid of it, you'll have quite a bit of work removing the > excess glass. That happened to me, but the consolation is > that when you get rid of the turned edge, you *will* have a > good polish. > > > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From gfbrandenburg at yahoo.com Tue Jul 14 06:59:05 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Mon, 13 Jul 2009 14:59:05 -0700 (PDT) Subject: [ATM] Polishing First Mirror In-Reply-To: Message-ID: <530038.31614.qm@web111512.mail.gq1.yahoo.com> One other thing. I have been promoting the use of the little Radio Shack microscopes, but based on feedback from Bill B, I want to modify what I have said. (1) it's important to have fresh batteries in there to illuminate any possible pits, or you will miss some of them. (2) when you think it's polished out, make sure you turn the magnification up as high as possible, because you will miss some of the pits. (3) when you can't see any more pits with the microscope, then pull out a laser pointer and shine it, at about a 40 to 60 degree angle from the vertical, all over the surface of the CLEAN mirror. Where it's less polished out, you will see more of a reflection than where it's more polished out. (And it's often the case that the edge polishes last.) Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) > From b-hamburger at artinso.com Tue Jul 14 08:03:45 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Tue, 14 Jul 2009 01:03:45 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <4A5BA4CC.9090806@gfphoto.com> References: <4A5BA4CC.9090806@gfphoto.com> Message-ID: <00d401ca040e$2ede8a30$8c9b9e90$@com> > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Gary Fuchs > Sent: lunes, 13 de julio de 2009 23:19 > To: 'ATM list' > Subject: Re: [ATM] Polishing First Mirror > > > > With due respect, I don't agree with the attitude of the above. Fair enough. It's a free world and fortunately we don't all share the same opinion, as that would be the end of any constructive discussion. > I object to the notion that we should be prevented from knowing things: > by > our betters and for our own good - because we may be too weak to avoid > certain temptations our betters wouldn't (or did?) succumb to. As I said, I offer MY opinion on the topic. It may well be that I am the only telescope maker who displays such weakness, but quite frankly, I don't think so. > > "You will feel tempted not to finish polishing in order not to spoil the > good shape of the mirror." > > Is this something you know about this person in particular, or the > general > rule it appears to be? You in that context stands as a synonym for ONE (one will feel tempted...) > I think it's just as likely that one would be encouraged to continue to > a > full polish by good test results. Or, if there was a problem, be > encouraged > to take corrective action along the way. As I said my commentary displays my view of the issue. Certainly Brad is quite capable to distil from all responses he received what he needs to know and I don't think he feels discouraged by my reply in any way or even obliged to follow the path I laid out. Berthold From mbartels at bbastrodesigns.com Tue Jul 14 09:56:31 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Mon, 13 Jul 2009 17:56:31 -0700 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> References: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> Message-ID: <01dd01ca041d$f87329a0$e9597ce0$@com> >>> During collimation, assuming that you are also adjusting the primary, Universally, this is how optical alignment is accomplished. BUT, it is not the *only* approach in town... Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Anish Mangal Sent: Monday, July 13, 2009 1:48 PM To: Jack Swaton @ Starry Host Cc: atm Subject: Re: [ATM] Does Collimation change where the scope points Theoretically it should change... During collimation, assuming that you are also adjusting the primary, changing the alignment of the primary will change where it is pointing to (but not by a very big deal). Ideally the primary mirror should be aligned to the telescope's truss/tube for a well collimated scope, otherwise it may cause vignetting. After collimation, you'll also need to realign the finder-scope with the telescope. Anish New Delhi, India On Tue, Jul 14, 2009 at 1:58 AM, Jack Swaton @ Starry Host < jack.swaton at starryhost.com> wrote: > Here's a question for you all: > > > > "Does collimation change where your scope points?" > > > > I have completed a tandem 13" newt project (using old Coulters). As I get > the two tubes to point at the same object so I can view at the same time a > 2nd observer is viewing, does changing the collimation of either tube > change > where that tube is pointing? > > > > I am having difficulty testing this in the field because of confounding > factors (such as mount stability, ability to see a fixed object such as the > North Star, etc). Just thought you might have a good theory and two cents. > > > > Thanks, > > Jack Swaton > > www.StarryHost.com > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > _______________________________________________ ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Tue Jul 14 10:06:31 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Mon, 13 Jul 2009 18:06:31 -0700 Subject: [ATM] astigmatism tests In-Reply-To: <006901ca0390$c0ba01b0$422e0510$@com> References: <006901ca0390$c0ba01b0$422e0510$@com> Message-ID: <01de01ca041f$57261010$05723030$@com> "Muskrat" is a good safety word. Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Berthold Hamburger Sent: Monday, July 13, 2009 1:06 AM To: 'Richard Schwartz' Cc: atm at atmlist.net Subject: Re: [ATM] astigmatism tests Richard, That reminds me of an advice you gave to an aspiring telescope maker some 10-12 years ago about making a pitch lap. If I remember correctly, the poor lad was told to boil turpentine on the kitchen stove before mixing it with pitch in order to make his first (and probably last) polishing lap. Anyway, I think he was told (just) in time that your suggestion was a hoax and lives happily ever since.... I guess no rescuer is needed presently, but maybe we could agree on a secret moniker to safely identify and separate hoax from true wisdom. After all, all those messages end up in the archives and some poor guy might really end up cementing his glass to a metal backing one day, because he read your message out of context. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Richard Schwartz > Sent: lunes, 13 de julio de 2009 6:03 > To: 'Jeff Baldwin'; 'atm' > Subject: Re: [ATM] astigmatism tests > > I suggest that you glue the mirror to a stiff metal plate so that it can > not > flex. Just use a very thin layer of epoxy, and slide to mirror around a > bit > before the epoxy gets stiff. Be sure that the glue layer is thin and > that > there are no air bubbles in it behind the mirror. You will get better > adhesion if the back of the mirror is fine ground on the same metal > plate it > is to be bonded to. Then you should add mirror clips around the edge, > and > make them really tight, for safety and to assure that nothing will > rattle > loose in there. > > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of > Jeff Baldwin > Sent: Saturday, July 11, 2009 5:07 PM > To: atm > Subject: [ATM] astigmatism tests > > > Hi ATMers: > I am about 2 hours in to polishing a 24" f/3.6, the thickness at the > edge is > about 1.35". I am astigmatism testing before I continue. The mirror was > mounted on two sheets of 3/4" plywood with a 1" strap contacting the > mirror > for about 140 degrees. Short pile carpet supports the mirror against the > plywood. > > The vertical diameter has an ROC a bit longer than the horizontal > diameter. > I rotated the mirror 90 degrees, and again, the ROC is a bit longer on > the > vertical axis. Since the astigmatism did not rotate, my mirror holder is > bending the glass. > > I then whipped up a 9-pt flotation cell for the mirror stand, and again, > the > vertical axis is a bit longer than the horizontal axis regardless of > mirror > orientation. So I eliminated the back support. I would like to confirm > that > I have no astigmatism in the glass. Seeing that my mount creates > astigmatism > does not mean that my mirror has none. But I need to elliminate this > system > error. > > I have heard urban legends regarding how many degrees the strap should > contact the mirror, anywhere form 180 degrees, to 160 to 170, and many > other > ideas. I know that when I pose this question to the group I will get > even > more of these answers. Nonetheless, I am asking two questions. First, > what > is the concensus on degrees of contact for the strap, and second, how > close > to the front edge and back edge ought the strap stay back from. > Meanwhile I > am going to support the edge with about 170 degrees of contact and > possibly > use a thinner strap, and I will let you know what the results are. > > Thanks, will enjoy hearing from all of you. > Bald > > Jeff and Glenda Baldwin > Lathrop, CA > www.stocktonastro.org _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ _______________________________________________ ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Tue Jul 14 10:06:31 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Mon, 13 Jul 2009 18:06:31 -0700 Subject: [ATM] astigmatism tests In-Reply-To: References: <734485.93509.qm@web112414.mail.gq1.yahoo.com> Message-ID: <01e201ca041f$5b43d5b0$11cb8110$@com> >>> my AVG security instantly gave me a warning And you BELIEVE it??? Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of stainless_steel at suddenlink.net Sent: Monday, July 13, 2009 6:11 AM To: Mark Cowan; atm; Jeff Baldwin Subject: Re: [ATM] astigmatism tests Mark, all- When I visited the URL for your picture, my AVG security instantly gave me a warning that the file was infected with dangerous malware. It warned me that any attempt to repair the file, quarantine the file, etc.,, could result in a crash of the operating system, at worst. Just thought you ought to know what the latest version of AVG said about the picture, which is a very good one, making everything clear. D-LZ130 ----- Original Message ----- From: "Mark Cowan" To: "atm" ; "Jeff Baldwin" Sent: Monday, July 13, 2009 3:04 AM Subject: Re: [ATM] astigmatism tests > > I've no idea how you can get somebody to supply a consensus on this, but > FWIW I'll say that you're doing a couple things wrong supporting this 18:1 > mirror this way on the test stand. A lot of experimentation zeroed in on > the best test stand support for thin mirrors: > > 1) Lose the strap, use pegs where the pegs have a grommet or similar > fitting falling just outside the COG of the glass disk, oriented at 90 > degrees supporting the base of the glass. > > 2) No flexible back (carpet or cell), they don't do squat for vertical > testing. Produce a reasonably flat back support into which the pegs > insert in 90 degree holes, the support can be made of something like 1/2" > Corian countertop against a solid backer (this is what I'm using up to > 20"), whatever it is it must be quite flat and the back of the mirror > likewise. > > Then the mirror is just placed onto the backing and lowered into contact > with the grommets on the pegs gently, with no other pressure involved. > The large contact area of the back plus the small contact area on the pegs > easily counteracts the potato chipping you're seeing from the combo of > sling/carpet or sling/cell - I've seen this happen in experimenting with > supporting _full thick_ 12.5" Pyrex variously on a sling/foam/bubble > wrap... > > With proper support the mirror can't bend over because it's prevented from > this by the back support, and it can't bend forward at the base because > it's held by the contact points. Neither are true with slings and > flexible back supports. > > This setup allows me to easily verify lack of astigmatism in mirrors down > to about 20:1 aspect ratio, using a precision pinhole source and a 12mm EP > to view the resulting pattern through the caustic. > > Here's a picture of what I'm talking about with the pegs (I put some vinyl > hose behind the grommets to ensure alignment as needed): > > http://www.raddobs.com/atm/peg%20support.jpg > > Best, > Mark > > --- On Sat, 7/11/09, Jeff Baldwin wrote: > >> From: Jeff Baldwin >> Subject: [ATM] astigmatism tests >> To: "atm" >> Date: Saturday, July 11, 2009, 5:07 PM >> Hi ATMers: >> I am about 2 hours in to polishing a 24" f/3.6, the >> thickness at the edge is about 1.35". I am astigmatism >> testing before I continue. The mirror was mounted on two >> sheets of 3/4" plywood with a 1" strap contacting the mirror >> for about 140 degrees. Short pile carpet supports the mirror >> against the plywood. >> >> The vertical diameter has an ROC a bit longer than the >> horizontal diameter. I rotated the mirror 90 degrees, and >> again, the ROC is a bit longer on the vertical axis. Since >> the astigmatism did not rotate, my mirror holder is bending >> the glass. >> >> I then whipped up a 9-pt flotation cell for the mirror >> stand, and again, the vertical axis is a bit longer than the >> horizontal axis regardless of mirror orientation. So I >> eliminated the back support. I would like to confirm that I >> have no astigmatism in the glass. Seeing that my mount >> creates astigmatism does not mean that my mirror has none. >> But I need to elliminate this system error. >> >> I have heard urban legends regarding how many degrees the >> strap should contact the mirror, anywhere form 180 degrees, >> to 160 to 170, and many other ideas. I know that when I pose >> this question to the group I will get even more of these >> answers. Nonetheless, I am asking two questions. First, what >> is the concensus on degrees of contact for the strap, and >> second, how close to the front edge and back edge ought the >> strap stay back from. Meanwhile I am going to support the >> edge with about 170 degrees of contact and possibly use a >> thinner strap, and I will let you know what the results >> are. >> >> Thanks, will enjoy hearing from all of you. >> Bald >> >> Jeff and Glenda Baldwin >> Lathrop, CA >> www.stocktonastro.org >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ ---------------------------------------------------------------------------- ---- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.375 / Virus Database: 270.13.12/2235 - Release Date: 07/13/09 05:56:00 _______________________________________________ ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Tue Jul 14 10:06:31 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Mon, 13 Jul 2009 18:06:31 -0700 Subject: [ATM] unequal tool and mirror blank In-Reply-To: <249428.79496.qm@web80505.mail.mud.yahoo.com> References: <249428.79496.qm@web80505.mail.mud.yahoo.com> Message-ID: <01e801ca041f$62176c80$26464580$@com> The 5:6 ratio is a magical ratio that will maintain the radius of curvature. It's to be encouraged! Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of D ERIC ALLEN Sent: Monday, July 13, 2009 9:58 AM To: atm at atmlist.net Subject: [ATM] unequal tool and mirror blank Is there any problem with grinding a six-inch blank against a five-inch blank?? This is for my cass secondary, so I'll be making the secondary out of the five incher and the test plate out of the six inch.? I will probably make plaster tools for polishing and figuring, but was hoping to be able to grind the blanks against each other.? Will this work?? Anything special I need to do?? Can I do both?5" on top and?6" on top? Thanks Eric _______________________________________________ ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Tue Jul 14 10:06:31 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Mon, 13 Jul 2009 18:06:31 -0700 Subject: [ATM] Polishing First Mirror In-Reply-To: <1A260D02-D1CD-4565-B293-F25A91F73A36@psu.edu> References: <008201ca01fc$b0e2cb40$12a861c0$@com> <42ee1e6c0907122149y3f255edcpbb7ef47fa05d0e3f@mail.gmail.com> <42ee1e6c0907130137p1f0fcdffl75caab2033e08230@mail.gmail.com> <1A260D02-D1CD-4565-B293-F25A91F73A36@psu.edu> Message-ID: <01ea01ca041f$669e2d20$33da8760$@com> >>> Some folks like to talk about going directly to the parabola. I think that is an advanced technique, and until a person learns to get to a sphere, then parabolize, they will be better served. There is a lot of getting the process under control that is needed before one is ready to go for the parabola on one shot. <<< I wholeheartedly agree. The ability to demonstrate control over the figure when the figure is spherical and therefore much easier to test is key. Mel Bartels From jack.swaton at starryhost.com Tue Jul 14 10:12:47 2009 From: jack.swaton at starryhost.com (Jack Swaton @ Starry Host) Date: Mon, 13 Jul 2009 18:12:47 -0700 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: <01dd01ca041d$f87329a0$e9597ce0$@com> References: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> <01dd01ca041d$f87329a0$e9597ce0$@com> Message-ID: You tease me, Mel! I believe the system I am employing will hopefully mitigate this problem, but these responses so far do give me an order to my steps at the very least. They also explain why some very clever arrangements in the past proved...er...embarrasing! 1) Collimate the individual scopes 2) Align the two scopes to each other 3) Don't reverse #1 and #2! But about "the other game in town"...? Jack -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Mel Bartels Sent: Monday, July 13, 2009 5:57 PM To: 'atm' Subject: Re: [ATM] Does Collimation change where the scope points >>> During collimation, assuming that you are also adjusting the primary, Universally, this is how optical alignment is accomplished. BUT, it is not the *only* approach in town... Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Anish Mangal Sent: Monday, July 13, 2009 1:48 PM To: Jack Swaton @ Starry Host Cc: atm Subject: Re: [ATM] Does Collimation change where the scope points Theoretically it should change... During collimation, assuming that you are also adjusting the primary, changing the alignment of the primary will change where it is pointing to (but not by a very big deal). Ideally the primary mirror should be aligned to the telescope's truss/tube for a well collimated scope, otherwise it may cause vignetting. After collimation, you'll also need to realign the finder-scope with the telescope. Anish New Delhi, India On Tue, Jul 14, 2009 at 1:58 AM, Jack Swaton @ Starry Host < jack.swaton at starryhost.com> wrote: > Here's a question for you all: > > > > "Does collimation change where your scope points?" > > > > I have completed a tandem 13" newt project (using old Coulters). As I get > the two tubes to point at the same object so I can view at the same time a > 2nd observer is viewing, does changing the collimation of either tube > change > where that tube is pointing? > > > > I am having difficulty testing this in the field because of confounding > factors (such as mount stability, ability to see a fixed object such as the > North Star, etc). Just thought you might have a good theory and two cents. > > > > Thanks, > > Jack Swaton > > www.StarryHost.com > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > _______________________________________________ ATM mailing list http://www.atmlist.net/ _______________________________________________ ATM mailing list http://www.atmlist.net/ From atmpob at yahoo.com Tue Jul 14 10:25:04 2009 From: atmpob at yahoo.com (Dale Eason) Date: Mon, 13 Jul 2009 18:25:04 -0700 (PDT) Subject: [ATM] astigmatism update Message-ID: <670953.55514.qm@web54502.mail.re2.yahoo.com> What process and tester do you use to measure the different Focal Lengths? I forgot if you posted how much different they are as well. Dale Eason --- On Mon, 7/13/09, Jeff Baldwin wrote: > From: Jeff Baldwin > Subject: [ATM] astigmatism update > To: "atm" > Date: Monday, July 13, 2009, 2:36 PM > Hi gang; > I'm the one who posted the original issue. Here's my > update. > > I've tried a carpetted plywood with a sling at 140 degress, > I moved the sling to 180 degrees, I've replaced the carpet > with a 9-point flotation I derived off of PLOP, I've > replaced the sling with a wire (180 degrees), and I've > replaced the wire with two pegs at 90 degrees. I still have > a longer ROC for the vertical diameter than for the > horizontal diameter.? Furthermore, I would have > expected the mirror to relax vertically producing a shorter > ROC on the vertical diameter than for the horizontal > diameter, which is NOT the case. This must mean that the > mirror is falling back, not leaning forward. My next trial > will be with a formica style countertop board behind with > two pegs, but I'm also thinking that the mirror will seek > out 3 primary points of force against it. But I'm willing to > try it. How, then, would I deal with this in my telescope??? > I'm not going to put formica countertop in my telescope, I > hope. > > Thanks to all who have tossed in on this, both serious and > silly. After 300 mirrors, I'm not a total newbie, but am > perplexed by this particular project. This can't be entirely > that the mirror is too thin, many of you guys have been > doing mirrors with higher aspect ratios than my 18:1 and > have done so without the test stand destroying your > information. Thanks again everybody. > Bald > > Jeff and Glenda Baldwin > Lathrop, CA > www.stocktonastro.org > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From baldjeff at comcast.net Tue Jul 14 11:18:18 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Mon, 13 Jul 2009 19:18:18 -0700 Subject: [ATM] astigmatism update References: <670953.55514.qm@web54502.mail.re2.yahoo.com> Message-ID: <2FEF8566FB784275A4F099FE760DAE6D@glendaspc> When you move the eyepiece through the focus area, the vertical football shaped bundle of light minimizes its horizontal diameter, and when you move through the horizontal football, the bundle of light minimizes its vertical diameter. I consider these two locations to be the 'best' ROC of the two axes. I am not measuring these positions since I am not certain that this is legitimate, but qualitatively speaking, you can tell that there is a difference in ROC on the two axes. JBald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org ----- Original Message ----- From: "Dale Eason" To: "atm" Sent: Monday, July 13, 2009 6:25 PM Subject: Re: [ATM] astigmatism update What process and tester do you use to measure the different Focal Lengths? I forgot if you posted how much different they are as well. Dale Eason --- On Mon, 7/13/09, Jeff Baldwin wrote: > From: Jeff Baldwin > Subject: [ATM] astigmatism update > To: "atm" > Date: Monday, July 13, 2009, 2:36 PM > Hi gang; > I'm the one who posted the original issue. Here's my > update. > > I've tried a carpetted plywood with a sling at 140 degress, > I moved the sling to 180 degrees, I've replaced the carpet > with a 9-point flotation I derived off of PLOP, I've > replaced the sling with a wire (180 degrees), and I've > replaced the wire with two pegs at 90 degrees. I still have > a longer ROC for the vertical diameter than for the > horizontal diameter. Furthermore, I would have > expected the mirror to relax vertically producing a shorter > ROC on the vertical diameter than for the horizontal > diameter, which is NOT the case. This must mean that the > mirror is falling back, not leaning forward. My next trial > will be with a formica style countertop board behind with > two pegs, but I'm also thinking that the mirror will seek > out 3 primary points of force against it. But I'm willing to > try it. How, then, would I deal with this in my telescope??? > I'm not going to put formica countertop in my telescope, I > hope. > > Thanks to all who have tossed in on this, both serious and > silly. After 300 mirrors, I'm not a total newbie, but am > perplexed by this particular project. This can't be entirely > that the mirror is too thin, many of you guys have been > doing mirrors with higher aspect ratios than my 18:1 and > have done so without the test stand destroying your > information. Thanks again everybody. > Bald > > Jeff and Glenda Baldwin > Lathrop, CA > www.stocktonastro.org > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > _______________________________________________ ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Tue Jul 14 12:54:07 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Mon, 13 Jul 2009 20:54:07 -0700 Subject: [ATM] unequal tool and mirror blank In-Reply-To: <01e801ca041f$62176c80$26464580$@com> Message-ID: Mel, are you talking MOT or TOT here? -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Mel Bartels Sent: Monday, July 13, 2009 6:07 PM To: atm at atmlist.net Subject: Re: [ATM] unequal tool and mirror blank The 5:6 ratio is a magical ratio that will maintain the radius of curvature. It's to be encouraged! Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of D ERIC ALLEN Sent: Monday, July 13, 2009 9:58 AM To: atm at atmlist.net Subject: [ATM] unequal tool and mirror blank Is there any problem with grinding a six-inch blank against a five-inch blank?? This is for my cass secondary, so I'll be making the secondary out of the five incher and the test plate out of the six inch.? I will probably make plaster tools for polishing and figuring, but was hoping to be able to grind the blanks against each other.? Will this work?? Anything special I need to do?? Can I do both?5" on top and?6" on top? Thanks Eric _______________________________________________ ATM mailing list http://www.atmlist.net/ _______________________________________________ ATM mailing list http://www.atmlist.net/ From atmpob at yahoo.com Tue Jul 14 13:13:51 2009 From: atmpob at yahoo.com (Dale Eason) Date: Mon, 13 Jul 2009 21:13:51 -0700 (PDT) Subject: [ATM] astigmatism update Message-ID: <838644.85597.qm@web54502.mail.re2.yahoo.com> The eyepiece of what and/or what is the mirror focused on? An artificial star? What is your test setup? Some test setups can introduce astig besides that of induced by the stand. Dale Eason --- On Mon, 7/13/09, Jeff Baldwin wrote: > From: Jeff Baldwin > Subject: Re: [ATM] astigmatism update > To: "Dale Eason" , "atm" > Date: Monday, July 13, 2009, 9:18 PM > When you move the eyepiece through > the focus area, the vertical football shaped bundle of light > minimizes its horizontal diameter, and when you move through > the horizontal football, the bundle of light minimizes its > vertical diameter. I consider these two locations to be the > 'best' ROC of the two axes. I am not measuring these > positions since I am not certain that this is legitimate, > but qualitatively speaking, you can tell that there is a > difference in ROC on the two axes. > JBald From tillerman1 at videotron.ca Tue Jul 14 13:36:55 2009 From: tillerman1 at videotron.ca (George Anderson) Date: Tue, 14 Jul 2009 00:36:55 -0400 Subject: [ATM] astigmatism tests In-Reply-To: <723102.63867.qm@web112405.mail.gq1.yahoo.com> References: <723102.63867.qm@web112405.mail.gq1.yahoo.com> Message-ID: <4A5C0B67.20601@videotron.ca> What else but huile de verre, imported from France. But it must be extra virgin from the first pressing with only 10 PSI. George Anderson Montreal Canada Clears skies and good health Mark Cowan wrote: > What do you use to lubricate the tap, though? > > Mark > > --- On Mon, 7/13/09, Michael Coslo wrote: > > >> From: Michael Coslo >> Subject: Re: [ATM] astigmatism tests >> To: "Richard Schwartz" >> Cc: "ATM List" >> Date: Monday, July 13, 2009, 10:52 AM >> >> On Jul 13, 2009, at 12:03 AM, Richard Schwartz wrote: >> >> >>> I suggest that you glue the mirror to a stiff metal >>> >> plate so that it can not >> >>> flex. Just use a very thin layer of epoxy, and >>> >> slide to mirror around a bit >> >>> before the epoxy gets stiff. Be sure that the glue >>> >> layer is thin and that >> >>> there are no air bubbles in it behind the >>> >> mirror. You will get better >> >>> adhesion if the back of the mirror is fine ground on >>> >> the same metal plate it >> >>> is to be bonded to. Then you should add mirror >>> >> clips around the edge, and >> >>> make them really tight, for safety and to assure that >>> >> nothing will rattle >> >>> loose in there. >>> >> Hardly secure enough Richard. I personally drill and tap 12 >> 1/4-20 holes in the back of my mirror (real men use only >> full thickness blanks) and bolt the mirror onto the mirror >> cell. You've never lived until you've successfully run a tap >> through glass. >> >> >> -73 de Mike N3LI - >> >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> >> > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > > From baldjeff at comcast.net Tue Jul 14 13:44:26 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Mon, 13 Jul 2009 21:44:26 -0700 Subject: [ATM] astigmatism error discovered Message-ID: OK atmers, thanks to Mel, I now have my head out of my perforation. The test stand wasn't the issue, but rather the eyepiece and the ball (false star) were a bit too far off axis for an f/3.6 optic. It is an arrangement that has worked for years for me with slower mirrors (slower than f/3.6), but with this setup was creating the astigmatism. I reglued the ball onto my focuser, so the ball is still off axis a bit, but much closer, and the systematic astigmatism vanished. A lot of good came out of this. I learned more about straps and peg mounted mirrors, I learned to keep my angles small when performing this test, and I learned how to drill and tap (and lubricate) glass ;o). I also was able to see some great mirror cell designs from all you friends who sent me images of your mirror mounts. Roller bearings and grommets on drill rods were ideas I would not have considered, but are all awesome. Thanks guys, Bald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org From wkitty42 at windstream.net Tue Jul 14 13:49:04 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Tue, 14 Jul 2009 00:49:04 -0400 Subject: [ATM] astigmatism tests In-Reply-To: <6A30CDA3-31D2-4857-82EC-A479F68ED36B@psu.edu> References: <723102.63867.qm@web112405.mail.gq1.yahoo.com> <6A30CDA3-31D2-4857-82EC-A479F68ED36B@psu.edu> Message-ID: <4A5C0E40.20007@windstream.net> Michael Coslo wrote: > > On Jul 13, 2009, at 3:29 PM, Mark Cowan wrote: > >> >> What do you use to lubricate the tap, though? >> > Tears.. :LOL: and i actually started to pop off with "suet" or some other fatty animal material that the ancients may have had at their disposal :) From atmer at flash.net Tue Jul 14 13:59:31 2009 From: atmer at flash.net (Anthony Stillman) Date: Mon, 13 Jul 2009 21:59:31 -0700 (PDT) Subject: [ATM] Tapping glass Message-ID: <263682.91595.qm@web82004.mail.mud.yahoo.com> It is possible to tap glass, and granite. I did it by hand using a set of every increasing sized disposable (broken end) taps. I drilled the holes using a glass drill and a diamond burr on a flex shaft to open the hole up a bit. I filled the hole with hard wax and used 400 grit silicon carbide as the "lubricant." An automatic tapping tool on a lathe or mill would have made the job a lot easier. Anthony From wkitty42 at windstream.net Tue Jul 14 15:14:56 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Tue, 14 Jul 2009 02:14:56 -0400 Subject: [ATM] unequal tool and mirror blank In-Reply-To: <01e801ca041f$62176c80$26464580$@com> References: <249428.79496.qm@web80505.mail.mud.yahoo.com> <01e801ca041f$62176c80$26464580$@com> Message-ID: <4A5C2260.1040400@windstream.net> Mel Bartels wrote: > The 5:6 ratio is a magical ratio that will maintain the radius of curvature. > It's to be encouraged! and no muskrat in the works, eh? :P ;) > Mel Bartels > > > > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of > D ERIC ALLEN > Sent: Monday, July 13, 2009 9:58 AM > To: atm at atmlist.net > Subject: [ATM] unequal tool and mirror blank > > Is there any problem with grinding a six-inch blank against a five-inch > blank? This is for my cass secondary, so I'll be making the secondary out > of the five incher and the test plate out of the six inch. I will probably > make plaster tools for polishing and figuring, but was hoping to be able to > grind the blanks against each other. Will this work? Anything special I > need to do? Can I do both 5" on top and 6" on top? > Thanks From wkitty42 at windstream.net Tue Jul 14 15:20:08 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Tue, 14 Jul 2009 02:20:08 -0400 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: References: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> <01dd01ca041d$f87329a0$e9597ce0$@com> Message-ID: <4A5C2398.9060403@windstream.net> jack, it sounds very much like you are working with a "bino-scope" that "simply" has the pair of eyepieces split and rotated aside so that two people can look thru them individually instead of the eyepieces being together in the middle between the scopes for one person to look thru with a stereo view... is this a fair assessment?? Jack Swaton @ Starry Host wrote: > You tease me, Mel! > > I believe the system I am employing will hopefully mitigate this problem, > but these responses so far do give me an order to my steps at the very > least. They also explain why some very clever arrangements in the past > proved...er...embarrasing! > > 1) Collimate the individual scopes > 2) Align the two scopes to each other > 3) Don't reverse #1 and #2! > > But about "the other game in town"...? From bgilb5 at gmail.com Tue Jul 14 15:30:52 2009 From: bgilb5 at gmail.com (Brad Gilbert) Date: Tue, 14 Jul 2009 01:30:52 -0500 Subject: [ATM] Polishing First Mirror In-Reply-To: <01ea01ca041f$669e2d20$33da8760$@com> References: <008201ca01fc$b0e2cb40$12a861c0$@com> <42ee1e6c0907122149y3f255edcpbb7ef47fa05d0e3f@mail.gmail.com> <42ee1e6c0907130137p1f0fcdffl75caab2033e08230@mail.gmail.com> <1A260D02-D1CD-4565-B293-F25A91F73A36@psu.edu> <01ea01ca041f$669e2d20$33da8760$@com> Message-ID: <42ee1e6c0907132330o27d25034xcfda913c5f032f39@mail.gmail.com> How do I know if the pits I am seeing under laser light are too big and would take forever to polish out? On Mon, Jul 13, 2009 at 8:06 PM, Mel Bartels wrote: > >>> > Some folks like to talk about going directly to the parabola. I think > that is an advanced technique, and until a person learns to get to a > sphere, then parabolize, they will be better served. There is a lot of > getting the process under control that is needed before one is ready > to go for the parabola on one shot. > <<< > > I wholeheartedly agree. The ability to demonstrate control over the figure > when the figure is spherical and therefore much easier to test is key. > > Mel Bartels > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mjc5 at psu.edu Tue Jul 14 21:57:48 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Tue, 14 Jul 2009 08:57:48 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <4A5BA4CC.9090806@gfphoto.com> References: <4A5BA4CC.9090806@gfphoto.com> Message-ID: <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> On Jul 13, 2009, at 5:19 PM, Gary Fuchs wrote: > > I object to the notion that we should be prevented from knowing > things: by > our betters and for our own good - because we may be too weak to avoid > certain temptations our betters wouldn't (or did?) succumb to. Ouch! When I was a young Technician, a lot of experienced people gave me a lot of unwanted advice. They were not as smart as they thought they were. I though many of them were insufferable jerks. Bunch of dummies, they were not only not as smart as they thought, they spent way too much time telling me what to do and how to do it. After 3 or 4 years, I was amazed at how much they had learned....... (with apologies to Mark Twain) I think there is a lot of experience talking here. but... 1. most of us test before the mirror is fully polished, especially the new guys and gals. 2. On a first mirror, it can lead to a lot of problems, as the new person tackles two different things they don't know about at the same time. 3. It's good advice, and I really doubt that anyone is acting superior here. I only wish that I had *not* put my first mirror on the test stand too early, which is exactly what I did. I saw things from the back of the mirror and the test stand that I ascribed to the mirror surface. I experimented with corrections, not only not actually knowing how to make the corrections, but making unneeded ones. I ended up giving myself problems that didn't exist before. One good thing about that is that by the time I was finished, I had about 5 mirrors worth of experience in testing and polishing. There really is a lot to be said for the first timer to avoid putting the mirror on the test stand too early, unless there is an experienced worker there with them. Obviously for the more experienced, a quick polish followed by a general look see on the test stand can point out gross problems. > > I think it's just as likely that one would be encouraged to continue > to a > full polish by good test results. Or, if there was a problem, be > encouraged > to take corrective action along the way. There are many paths of course, but the new person doesn't necessarily know the method of corrective action. I a mirror that isn't completely polished, I have to say that short of gross problems and their corrections, most corrective action is a bit premature. The surface changes naturally as we polish. That being said, it's a huge temptation to put that mirror on the stand and have at it. So admonitions against it are largely ignored. But sometimes those admonitions come from experience. I'm a bit ambivalent about the whole thing. The way I screwed up my first mirror was tied to my premature look at it, but the experience I got fixing up my mistakes made me a better glass pusher. -73 de Mike N3LI - From gfbrandenburg at yahoo.com Tue Jul 14 23:59:24 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Tue, 14 Jul 2009 07:59:24 -0700 (PDT) Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907132330o27d25034xcfda913c5f032f39@mail.gmail.com> Message-ID: <487235.69698.qm@web111509.mail.gq1.yahoo.com> If you can only see them as reflections under the laser beam, and not as pits under a magnifying glass or small microscope, then you can safely relax. They will definitely polish out. If you can see the pits with your naked eye and with no laser aid, then they might not polish out in any reasonable time. That's my 2 shekels. Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Tue, 7/14/09, Brad Gilbert wrote: > From: Brad Gilbert > Subject: Re: [ATM] Polishing First Mirror > To: atm at atmlist.net > Date: Tuesday, July 14, 2009, 2:30 AM > How do I know if the pits I am seeing > under laser light are too big and > would take forever to polish out? > > On Mon, Jul 13, 2009 at 8:06 PM, Mel Bartels wrote: > > > >>> > > Some folks like to talk about going directly to the > parabola. I think > > that is an advanced technique, and until a person > learns to get to a > > sphere, then parabolize, they will be better served. > There is a lot of > > getting the process under control that is needed > before one is ready > > to go for the parabola on one shot. > > <<< > > > > I wholeheartedly agree.? The ability to > demonstrate control over the figure > > when the figure is spherical and therefore much easier > to test is key. > > > > Mel Bartels > > > > > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From gfbrandenburg at yahoo.com Wed Jul 15 00:05:04 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Tue, 14 Jul 2009 08:05:04 -0700 (PDT) Subject: [ATM] Fw: RE: Polishing First Mirror Message-ID: <838810.27427.qm@web111504.mail.gq1.yahoo.com> From: Richard Schwartz Subject: RE: [ATM] Polishing First Mirror To: "'Guy Brandenburg'" Date: Monday, July 13, 2009, 11:42 PM You forgot to mention that the edge is last to polish out because it has a poor final grind.? Usually this problem arises with a solid glass tool, and seldom with a channeled tool.? In fact, I recommend channeling solid glass tools after about #220 grit, when the approximate curve is established.? You can re-post this to the list if you like. > -----Original Message----- from Guy Brandenburg: > > One other thing. I have been promoting the use of the > little Radio Shack > microscopes, but based on feedback from Bill B, I want to > modify what I have > said. > (1) it's important to have fresh batteries in there to > illuminate any > possible pits, or you will miss some of them. > (2) when you think it's polished out, make sure you turn > the magnification > up as high as possible, because you will miss some of the > pits. > (3) when you can't see any more pits with the microscope, > then pull out a > laser pointer and shine it, at about a 40 to 60 degree > angle from the > vertical, all over the surface of the CLEAN mirror. Where > it's less polished > out, you will see more of a reflection than where it's more > polished out. > (And it's often the case that the edge polishes last.) > From mbartels at bbastrodesigns.com Wed Jul 15 00:32:04 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Tue, 14 Jul 2009 08:32:04 -0700 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: <4A5C2398.9060403@windstream.net> References: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> <01dd01ca041d$f87329a0$e9597ce0$@com> <4A5C2398.9060403@windstream.net> Message-ID: <00e901ca0498$414d8560$c3e89020$@com> > You tease me, Mel! > > I believe the system I am employing will hopefully mitigate this problem, > but these responses so far do give me an order to my steps at the very > least. They also explain why some very clever arrangements in the past > proved...er...embarrasing! There are three approaches to optical alignment that I see: 1. adjust primary mirror (what everyone does, for no particularly special reason other than "that's how everyone else does it and that's what we know to do") 2. build optical alignment into the telescope (what I come close to) 3. [surely you can figure this one out???] For #2, I first saw an example of this ~ 1970 from a wonderful telescope maker in eastern Washington. It's inspired me to build scopes that require no optical alignment. Most of my scopes, including disassemble portable guys, have not been re-aligned since first assembly. It's not that hard to do. Think "predictable" optical tube assembly designs. Mel Bartels From b-hamburger at artinso.com Wed Jul 15 01:08:48 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Tue, 14 Jul 2009 18:08:48 +0200 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: <00e901ca0498$414d8560$c3e89020$@com> References: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> <01dd01ca041d$f87329a0$e9597ce0$@com> <4A5C2398.9060403@windstream.net> <00e901ca0498$414d8560$c3e89020$@com> Message-ID: <011c01ca049d$6306ff60$2914fe20$@com> That's very interesting! Could you elaborate on #2? What are the major design principles to achieve this, considering that by nature we already design around the optical axis and think concentrically? Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > There are three approaches to optical alignment that I see: > > 1. adjust primary mirror (what everyone does, for no particularly > special > reason other than "that's how everyone else does it and that's what we > know > to do") > 2. build optical alignment into the telescope (what I come close to) > 3. [surely you can figure this one out???] > > For #2, I first saw an example of this ~ 1970 from a wonderful telescope > maker in eastern Washington. It's inspired me to build scopes that > require > no optical alignment. Most of my scopes, including disassemble portable > guys, have not been re-aligned since first assembly. It's not that hard > to > do. Think "predictable" optical tube assembly designs. > > Mel Bartels > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From ericandroberta at sbcglobal.net Wed Jul 15 03:47:47 2009 From: ericandroberta at sbcglobal.net (D ERIC ALLEN) Date: Tue, 14 Jul 2009 11:47:47 -0700 (PDT) Subject: [ATM] Slumped blank Message-ID: <748825.8788.qm@web80504.mail.mud.yahoo.com> Mr. Clyde Fishburn of the Indiana Astronomical Society passed away a few years ago, and his unfinished 20" mirror was donated to the society.? I have volunteered to finish the mirror.? It is a slumped blank with a convex back.? What kind of suspension does one use?under a mirror with a convex back?? Is it easier to flatten the back, and if so, will grinding the back flat affect the shape of the front?? The mirror is polished, but not figured.? Not sure how to proceed. Eric From mbartels at bbastrodesigns.com Wed Jul 15 04:35:06 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Tue, 14 Jul 2009 12:35:06 -0700 Subject: [ATM] Slumped blank In-Reply-To: <748825.8788.qm@web80504.mail.mud.yahoo.com> References: <748825.8788.qm@web80504.mail.mud.yahoo.com> Message-ID: <016301ca04ba$395c2a10$ac147e30$@com> I strongly suggest NOT grinding the back flat. The curved back provides significant strength to resist flexing. My meniscus mirrors use the same support as any other mirror, with the flotation pieces having a slight angle to them. Really, no big deal and insignificant. For grinding and polishing, I use a soft backing that has a tad more cushion near the edge, forming a very shallow bowl. Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of D ERIC ALLEN Sent: Tuesday, July 14, 2009 11:48 AM To: atm at atmlist.net Subject: [ATM] Slumped blank Mr. Clyde Fishburn of the Indiana Astronomical Society passed away a few years ago, and his unfinished 20" mirror was donated to the society.? I have volunteered to finish the mirror.? It is a slumped blank with a convex back.? What kind of suspension does one use?under a mirror with a convex back?? Is it easier to flatten the back, and if so, will grinding the back flat affect the shape of the front?? The mirror is polished, but not figured.? Not sure how to proceed. Eric _______________________________________________ ATM mailing list http://www.atmlist.net/ From rmay at nethere.com Wed Jul 15 05:02:42 2009 From: rmay at nethere.com (Bob May) Date: Tue, 14 Jul 2009 13:02:42 -0700 Subject: [ATM] Does Collimation change where the scope points References: Message-ID: <003801ca04be$0d4e19c0$61fe1345@amd> All telescopes will change their collimation to some degree or another, depending upon how rigid they are. For a binoscope, the requirements for rigidity are a bit stiffer than for a single scope. You may need to insure that the scope isn't flexing about as you change the attitude of it before you go any further. Find out what is moving and figure out what needs to be done with the upper cage support to get the rigidity up to where you don't notice the changes. You could even be having a problem like the secondary moving about with the attitude changes which will do major destruction to the alignment. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Wed Jul 15 05:14:41 2009 From: rmay at nethere.com (Bob May) Date: Tue, 14 Jul 2009 13:14:41 -0700 Subject: [ATM] Polishing First Mirror References: <008201ca01fc$b0e2cb40$12a861c0$@com><42ee1e6c0907122149y3f255edcpbb7ef47fa05d0e3f@mail.gmail.com><42ee1e6c0907130137p1f0fcdffl75caab2033e08230@mail.gmail.com><1A260D02-D1CD-4565-B293-F25A91F73A36@psu.edu><01ea01ca041f$669e2d20$33da8760$@com> <42ee1e6c0907132330o27d25034xcfda913c5f032f39@mail.gmail.com> Message-ID: <004d01ca04bf$b928bd80$61fe1345@amd> Brad, that is a very good question! I generally have learned to get rid of the pits of larger grits before going on to the next grit level. As a result, I don't have much in the way of finding pits that don't polish out quickly. The unfortunate part of this is that you may have to go up as far as 320 grit to get rid of the ones that don't go away which means a lot more of grinding. Generally tho, if you take an hour to polish out most of the pits and have one or a few for every square inch and they don't go away after another 3 hours of polishing, it is time to set back and figure out if you want to go back to grinding. I usually consider 25 micron far enough for a first try. Not a happy situation but sometimes it is necessary for a first timer. If there are still a lot of pits in the glass, it usually is that you just haven't polished enough. Please note that if the glass is smoothly moving over the lap with no real resistance, you're not polishing. There needs to be a lot of resistance (like you're moving through molassass) to the motion to do a good polishing action. It is real easy to put too much water and/or CeO on the lap and thus the polishing action stops working well. Good Luck! Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Wed Jul 15 05:18:41 2009 From: rmay at nethere.com (Bob May) Date: Tue, 14 Jul 2009 13:18:41 -0700 Subject: [ATM] Polishing First Mirror References: <4A5BA4CC.9090806@gfphoto.com> Message-ID: <005001ca04c0$4852d360$61fe1345@amd> Testing a mirror before it is fully polished out is more of an exercise in gettng used to setting up the Foucault test and the curiosity of what is happening than a guide for making changes to the polishing stroke. However, a deep hole in the middle is an indication that the stroke is too long while a turned edge (usually seen best even before setting the mirror on the test stand as the edge will still be frosty) usually is best done by flipping the mirror and lap and working the edge more than the center. Remember that whichever is on top tends to turn concave so putting the mirror on the bottom will work the edge more than the center and you will gradually get the edge polished out and finally get that polishing action to the center. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Wed Jul 15 05:22:16 2009 From: rmay at nethere.com (Bob May) Date: Tue, 14 Jul 2009 13:22:16 -0700 Subject: [ATM] astigmatism error discovered References: Message-ID: <005301ca04c0$c8762ba0$61fe1345@amd> Yep, with faster mirrors, the difference in location of the source and KE need to be closer to keep the "astig." that you see from being apparent. What you actually ar seeing really isn't astig. but rather looking at an elipsoid. This is because the source and KE aren't together so you're not looking at the cneter of the ROC but rather at the two points a slight elipsoid focal points are producing. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Wed Jul 15 05:25:56 2009 From: rmay at nethere.com (Bob May) Date: Tue, 14 Jul 2009 13:25:56 -0700 Subject: [ATM] Tapping glass References: <263682.91595.qm@web82004.mail.mud.yahoo.com> Message-ID: <005601ca04c1$4bb47f80$61fe1345@amd> The use of a single point cutter using abrasives also works. This does mean that you have to keep going up and down the hole. Running a regular tap through the hole will just break the glass as it doesn't like local stresses on that order although the use of a tap and abrasives and running it back and forth a whole lot as the abrasives do their job can eventually get the job done. The secret there is to let the abrasive do the work rather than the steel of the tap. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Wed Jul 15 05:33:15 2009 From: rmay at nethere.com (Bob May) Date: Tue, 14 Jul 2009 13:33:15 -0700 Subject: [ATM] Slumped blank References: <748825.8788.qm@web80504.mail.mud.yahoo.com> Message-ID: <005f01ca04c2$51aded80$61fe1345@amd> Two ways that I've done it are: 1. Make a flat back from pourable stone 2. Make a stepped/curved back from plywood and cover with something flexible like two layers or so of drawer liner or some carpet. You will also want to turn the glass on the support frequently to keep astig. from the incomplete support from affecting the figure. For example, a 13" 1/2" thick surface will want to be turned about every minute to keep the astig. from affecting the surface. Been there and did that on some glass. Got another guy working on a 17" 3/4" mirror that polished a lot of astig. into his mirror and he's now doing MOT to get it out. Better is to put the glass on the top and thus the forces on the polishing surface will mostly be the weight of the glass, no additional weights other than your hands which must move about the glass back regularly. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From mjc5 at psu.edu Wed Jul 15 05:50:17 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Tue, 14 Jul 2009 16:50:17 -0400 Subject: [ATM] Slumped blank In-Reply-To: <748825.8788.qm@web80504.mail.mud.yahoo.com> References: <748825.8788.qm@web80504.mail.mud.yahoo.com> Message-ID: On Jul 14, 2009, at 2:47 PM, D ERIC ALLEN wrote: > Mr. Clyde Fishburn of the Indiana Astronomical Society passed away a > few years ago, and his unfinished 20" mirror was donated to the > society. I have volunteered to finish the mirror. It is a slumped > blank with a convex back. What kind of suspension does one use > under a mirror with a convex back? Is it easier to flatten the > back, and if so, will grinding the back flat affect the shape of the > front? The mirror is polished, but not figured. Not sure how to > proceed. Welcome Eric! You don't want to flatten the back. You also have taken on a pretty big task here. If the mirror is polished, you need to ascertain the shape it is in. So you are past a lot of the work. I'm assuming that you are pretty new to the sport, and since you have a nearly finished product, do you know of any other ATM'ers in the vicinity? They might be able you help you out to see just what shape that mirror is in. Slumping a mirror is done to pregenerate a curve for a couple reasons, one is so that there is less grinding involved, and another possibility is as an adjunct to a relatively thin mirror. The mirror cell of such a mirror is a little more complex than a flat back mirror, but similar. It just has to accommodate the shape. A few questions as you start: Do you know what type of glass is used. It's probably plate, but could be Pyrex. Focal length? Other stuff.... Most likely you'll need to build a polishing tool and holder for working the mirror, unless you were lucky enough to get them with the mirror. The pitch would probably have hardened a bit. Did you get a supply of Cerium Oxide or other polishing compound? -73 de Mike N3LI - From gary at gfphoto.com Wed Jul 15 11:37:49 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Tue, 14 Jul 2009 22:37:49 -0400 Subject: [ATM] Tapping glass In-Reply-To: <263682.91595.qm@web82004.mail.mud.yahoo.com> References: <263682.91595.qm@web82004.mail.mud.yahoo.com> Message-ID: <4A5D40FD.5050001@gfphoto.com> Very neat! How thick is the glass and what are you screwing into it, or was it just an experiment? Gary Fuchs Anthony Stillman wrote: > It is possible to tap glass, and granite. I did it by hand using a set of every increasing sized disposable (broken end) taps. I drilled the holes using a glass drill and a diamond burr on a flex shaft to open the hole up a bit. I filled the hole with hard wax and used 400 grit silicon carbide as the "lubricant." An automatic tapping tool on a lathe or mill would have made the job a lot easier. > > Anthony > > From gary at gfphoto.com Wed Jul 15 12:01:05 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Tue, 14 Jul 2009 23:01:05 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> References: <4A5BA4CC.9090806@gfphoto.com> <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> Message-ID: <4A5D4671.1070404@gfphoto.com> I'd like to point out that it was the attitude that I objected to. And that's something I've run across many times. In one sense "Grind more, worry less" is fine advice - when you're looking over someone's shoulder and see all the circumstances and will be there to catch any problems. But when you're a beginner and don't know which advice is appropriate to your situation or what tolerance there is for deviation from that advice, then I maintain that it's better to have more knowledge than less. In this case, enough to understand the parameters of what you're up against at least so far as knowing what the next couple of steps will bring. If the maker is capable of making a decision about what they've been told here - possibly the only personalized advice they may be receiving - then certainly they can handle being told how to test for being polished out and that they need to get there before calling it ready to figure. If they can't do that why would they follow any advice? Gary Fuchs Michael Coslo wrote: >
> On Jul 13, 2009, at 5:19 PM, Gary Fuchs wrote: > >> >> I object to the notion that we should be prevented from knowing >> things: by >> our betters and for our own good - because we may be too weak to avoid >> certain temptations our betters wouldn't (or did?) succumb to. > > Ouch! > > When I was a young Technician, a lot of experienced people gave me a > lot of unwanted advice. They were not as smart as they thought they > were. I though many of them were insufferable jerks. Bunch of dummies, > they were not only not as smart as they thought, they spent way too > much time telling me what to do and how to do it. > > After 3 or 4 years, I was amazed at how much they had learned....... > > (with apologies to Mark Twain) > > I think there is a lot of experience talking here. but... > > 1. most of us test before the mirror is fully polished, especially the > new guys and gals. > > 2. On a first mirror, it can lead to a lot of problems, as the new > person tackles two different things they don't know about at the same > time. > > 3. It's good advice, and I really doubt that anyone is acting superior > here. > > I only wish that I had *not* put my first mirror on the test stand too > early, which is exactly what I did. I saw things from the back of the > mirror and the test stand that I ascribed to the mirror surface. I > experimented with corrections, not only not actually knowing how to > make the corrections, but making unneeded ones. I ended up giving > myself problems that didn't exist before. > > One good thing about that is that by the time I was finished, I had > about 5 mirrors worth of experience in testing and polishing. > > There really is a lot to be said for the first timer to avoid putting > the mirror on the test stand too early, unless there is an experienced > worker there with them. Obviously for the more experienced, a quick > polish followed by a general look see on the test stand can point out > gross problems. > >> >> I think it's just as likely that one would be encouraged to continue >> to a >> full polish by good test results. Or, if there was a problem, be >> encouraged >> to take corrective action along the way. > > There are many paths of course, but the new person doesn't necessarily > know the method of corrective action. I a mirror that isn't completely > polished, I have to say that short of gross problems and their > corrections, most corrective action is a bit premature. The surface > changes naturally as we polish. > > That being said, it's a huge temptation to put that mirror on the > stand and have at it. So admonitions against it are largely ignored. > But sometimes those admonitions come from experience. I'm a bit > ambivalent about the whole thing. The way I screwed up my first mirror > was tied to my premature look at it, but the experience I got fixing > up my mistakes made me a better glass pusher. > > > -73 de Mike N3LI - > > > >
> From bgilb5 at gmail.com Wed Jul 15 13:16:26 2009 From: bgilb5 at gmail.com (Brad Gilbert) Date: Tue, 14 Jul 2009 23:16:26 -0500 Subject: [ATM] Polishing First Mirror In-Reply-To: <4A5D4671.1070404@gfphoto.com> References: <4A5BA4CC.9090806@gfphoto.com> <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> <4A5D4671.1070404@gfphoto.com> Message-ID: <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> Argh! Something is broke now. My mirror will not polish anymore at all, the center area looks good but the 50%-100% zone still has tons of tiny little pits when I shine a laser on the surface. Also, every time I look at the Ronchigram the surface shape didn't change at all. I don't know what I'm doing wrong, I've tried TOT, MOT. I've tried thin ceo and thick ceo. I've tried tons of pressure and little pressure. On Tue, Jul 14, 2009 at 10:01 PM, Gary Fuchs wrote: > I'd like to point out that it was the attitude that I objected to. And > that's something I've run across many times. > > In one sense "Grind more, worry less" is fine advice - when you're looking > over someone's shoulder and see all the circumstances and will be there to > catch any problems. But when you're a beginner and don't know which advice > is appropriate to your situation or what tolerance there is for deviation > from that advice, then I maintain that it's better to have more knowledge > than less. In this case, enough to understand the parameters of what you're > up against at least so far as knowing what the next couple of steps will > bring. > > If the maker is capable of making a decision about what they've been told > here - possibly the only personalized advice they may be receiving - then > certainly they can handle being told how to test for being polished out and > that they need to get there before calling it ready to figure. If they can't > do that why would they follow any advice? > > Gary Fuchs > > > > > Michael Coslo wrote: > >>
>> >> On Jul 13, 2009, at 5:19 PM, Gary Fuchs wrote: >> >> >>> I object to the notion that we should be prevented from knowing things: >>> by >>> our betters and for our own good - because we may be too weak to avoid >>> certain temptations our betters wouldn't (or did?) succumb to. >>> >> >> Ouch! >> >> When I was a young Technician, a lot of experienced people gave me a lot >> of unwanted advice. They were not as smart as they thought they were. I >> though many of them were insufferable jerks. Bunch of dummies, they were not >> only not as smart as they thought, they spent way too much time telling me >> what to do and how to do it. >> >> After 3 or 4 years, I was amazed at how much they had learned....... >> >> (with apologies to Mark Twain) >> >> I think there is a lot of experience talking here. but... >> >> 1. most of us test before the mirror is fully polished, especially the new >> guys and gals. >> >> 2. On a first mirror, it can lead to a lot of problems, as the new person >> tackles two different things they don't know about at the same time. >> >> 3. It's good advice, and I really doubt that anyone is acting superior >> here. >> >> I only wish that I had *not* put my first mirror on the test stand too >> early, which is exactly what I did. I saw things from the back of the mirror >> and the test stand that I ascribed to the mirror surface. I experimented >> with corrections, not only not actually knowing how to make the corrections, >> but making unneeded ones. I ended up giving myself problems that didn't >> exist before. >> >> One good thing about that is that by the time I was finished, I had about >> 5 mirrors worth of experience in testing and polishing. >> >> There really is a lot to be said for the first timer to avoid putting the >> mirror on the test stand too early, unless there is an experienced worker >> there with them. Obviously for the more experienced, a quick polish followed >> by a general look see on the test stand can point out gross problems. >> >> >>> I think it's just as likely that one would be encouraged to continue to a >>> full polish by good test results. Or, if there was a problem, be >>> encouraged >>> to take corrective action along the way. >>> >> >> There are many paths of course, but the new person doesn't necessarily >> know the method of corrective action. I a mirror that isn't completely >> polished, I have to say that short of gross problems and their corrections, >> most corrective action is a bit premature. The surface changes naturally >> as we polish. >> >> That being said, it's a huge temptation to put that mirror on the stand >> and have at it. So admonitions against it are largely ignored. But sometimes >> those admonitions come from experience. I'm a bit ambivalent about the whole >> thing. The way I screwed up my first mirror was tied to my premature look at >> it, but the experience I got fixing up my mistakes made me a better glass >> pusher. >> >> >> -73 de Mike N3LI - >> >> >> >>
>> >> > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From hermit at outofoptions.org Wed Jul 15 13:23:34 2009 From: hermit at outofoptions.org (hermit) Date: Wed, 15 Jul 2009 00:23:34 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> References: <4A5BA4CC.9090806@gfphoto.com> <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> Message-ID: <4A5D59C6.1090905@outofoptions.org> One reason to test early. You may have a turned edge from too long a stroke during grinding. If your Ronchi looks kind of parabolic now, you were too long with the strokes and will have to go back to fine grinding. 1/3 stroke means 1/6 over hang per side. Don't want to tell you how I learned that lesson..... Ken Lowther Brad Gilbert wrote: > Argh! Something is broke now. > > My mirror will not polish anymore at all, the center area looks good but the > 50%-100% zone still has tons of tiny little pits when I shine a laser on the > surface. Also, every time I look at the Ronchigram the surface shape didn't > change at all. > > I don't know what I'm doing wrong, I've tried TOT, MOT. I've tried thin ceo > and thick ceo. I've tried tons of pressure and little pressure. > > On Tue, Jul 14, 2009 at 10:01 PM, Gary Fuchs wrote: > > >> I'd like to point out that it was the attitude that I objected to. And >> that's something I've run across many times. >> >> In one sense "Grind more, worry less" is fine advice - when you're looking >> over someone's shoulder and see all the circumstances and will be there to >> catch any problems. But when you're a beginner and don't know which advice >> is appropriate to your situation or what tolerance there is for deviation >> from that advice, then I maintain that it's better to have more knowledge >> than less. In this case, enough to understand the parameters of what you're >> up against at least so far as knowing what the next couple of steps will >> bring. >> >> If the maker is capable of making a decision about what they've been told >> here - possibly the only personalized advice they may be receiving - then >> certainly they can handle being told how to test for being polished out and >> that they need to get there before calling it ready to figure. If they can't >> do that why would they follow any advice? >> >> Gary Fuchs >> >> >> >> >> Michael Coslo wrote: >> >> >>>
>>> >>> On Jul 13, 2009, at 5:19 PM, Gary Fuchs wrote: >>> >>> >>> >>>> I object to the notion that we should be prevented from knowing things: >>>> by >>>> our betters and for our own good - because we may be too weak to avoid >>>> certain temptations our betters wouldn't (or did?) succumb to. >>>> >>>> >>> Ouch! >>> >>> When I was a young Technician, a lot of experienced people gave me a lot >>> of unwanted advice. They were not as smart as they thought they were. I >>> though many of them were insufferable jerks. Bunch of dummies, they were not >>> only not as smart as they thought, they spent way too much time telling me >>> what to do and how to do it. >>> >>> After 3 or 4 years, I was amazed at how much they had learned....... >>> >>> (with apologies to Mark Twain) >>> >>> I think there is a lot of experience talking here. but... >>> >>> 1. most of us test before the mirror is fully polished, especially the new >>> guys and gals. >>> >>> 2. On a first mirror, it can lead to a lot of problems, as the new person >>> tackles two different things they don't know about at the same time. >>> >>> 3. It's good advice, and I really doubt that anyone is acting superior >>> here. >>> >>> I only wish that I had *not* put my first mirror on the test stand too >>> early, which is exactly what I did. I saw things from the back of the mirror >>> and the test stand that I ascribed to the mirror surface. I experimented >>> with corrections, not only not actually knowing how to make the corrections, >>> but making unneeded ones. I ended up giving myself problems that didn't >>> exist before. >>> >>> One good thing about that is that by the time I was finished, I had about >>> 5 mirrors worth of experience in testing and polishing. >>> >>> There really is a lot to be said for the first timer to avoid putting the >>> mirror on the test stand too early, unless there is an experienced worker >>> there with them. Obviously for the more experienced, a quick polish followed >>> by a general look see on the test stand can point out gross problems. >>> >>> >>> >>>> I think it's just as likely that one would be encouraged to continue to a >>>> full polish by good test results. Or, if there was a problem, be >>>> encouraged >>>> to take corrective action along the way. >>>> >>>> >>> There are many paths of course, but the new person doesn't necessarily >>> know the method of corrective action. I a mirror that isn't completely >>> polished, I have to say that short of gross problems and their corrections, >>> most corrective action is a bit premature. The surface changes naturally >>> as we polish. >>> >>> That being said, it's a huge temptation to put that mirror on the stand >>> and have at it. So admonitions against it are largely ignored. But sometimes >>> those admonitions come from experience. I'm a bit ambivalent about the whole >>> thing. The way I screwed up my first mirror was tied to my premature look at >>> it, but the experience I got fixing up my mistakes made me a better glass >>> pusher. >>> >>> >>> -73 de Mike N3LI - >>> >>> >>> >>>
>>> >>> >>> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> >> > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From jack.swaton at starryhost.com Wed Jul 15 13:34:41 2009 From: jack.swaton at starryhost.com (Jack Swaton @ Starry Host) Date: Tue, 14 Jul 2009 21:34:41 -0700 Subject: [ATM] Does Collimation change where the scope points In-Reply-To: <4A5CBF33.7060707@windstream.net> References: <47eee29a0907131347k4821fa70t553080ef2d713abf@mail.gmail.com> <01dd01ca041d$f87329a0$e9597ce0$@com> <4A5C2398.9060403@windstream.net> <1CB3F6FAD32148E6BE5B9586ABE9E2D7@MRBNOTEBOOK> <4A5CBF33.7060707@windstream.net> Message-ID: <88DEA46AA4C64D3A886EEEECDFC6579A@MRBNOTEBOOK> Interesting link to the bino scope. I've not seen any bino scope plans that I could actually discern how they aligned the scopes. With this approach I can see it. I may be able to adapt something. I'll post photos tomorrow hopefully! And yes, it is a tandem scope rather than a bino scope. Jack -----Original Message----- From: waldo kitty [mailto:wkitty42 at windstream.net] Sent: Tuesday, July 14, 2009 10:24 AM To: Jack Swaton @ Starry Host Subject: Re: [ATM] Does Collimation change where the scope points the only thing close that i can think of is james lerch's bino-scope stuff... his method of "linking" the two scopes together may be of some assistance to you? i don't know though as his seems to be two truss scopes on a common backplane (ie: rocker box) where each scope has it's own collimation and alignment settings... maybe your's is similar? anyway, here's a link to james' bino-scope stuff... http://lerch.no-ip.com/atm/ step's 14 and 15 (down the left menu frame) are about the actual scope "frame" stuff... i was thinking of exactly the layout shown in his prototype layout but with each OTA's secondary cage rotated so their eyepieces are at about 45 degrees toward the bottom outside corners of the rocker box instead of about 45 degrees to the bottom inside corners... but, since his is about the only bino-scope i've really looked at, it is pretty easy for me to be swayed more towards his methods... what i recall reading about your scope is that it is more of a dual-scope than a bino-scope... both are very similar and it seems that it would be very easy to convert from one to the other with a minor change or two... did you post a link to what you are working on in the list? i'm thinking so but i forget those things that get lost next after the wife, the girlfriend, the truck and the dog :rolleyes: :lol: ;) Jack Swaton @ Starry Host wrote: > Correct! > I have three altitude bearings and rocker: Left, Center, Right. The "inside" > bearings on the OTAs share a common wide center rocker. With the large > rocker/bearing combos on the inside, I can move the two scopes vertically > with each other and then clamp them together when the vertical alignment is > correct. Then I can shim the OTAs at the top to achieve horizontal > tandemness. At that point I clamp the upper OTAs together. > > The scope has only been up a couple of times so far but the concept seems > sound. I've had to correct some other urgent OTA and mount issues so now I'm > concentrating on the tandem alignment mechanism. > > I should know more tonight after my Silicone dries for the alt bearing > strips and I can test again. > > Jack > > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of > waldo kitty > Sent: Monday, July 13, 2009 11:20 PM > To: 'atm' > Subject: Re: [ATM] Does Collimation change where the scope points > > jack, it sounds very much like you are working with a "bino-scope" that > "simply" > has the pair of eyepieces split and rotated aside so that two people can > look > thru them individually instead of the eyepieces being together in the middle > > between the scopes for one person to look thru with a stereo view... is this > a > fair assessment?? > > Jack Swaton @ Starry Host wrote: >> You tease me, Mel! >> >> I believe the system I am employing will hopefully mitigate this problem, >> but these responses so far do give me an order to my steps at the very >> least. They also explain why some very clever arrangements in the past >> proved...er...embarrasing! >> >> 1) Collimate the individual scopes >> 2) Align the two scopes to each other >> 3) Don't reverse #1 and #2! >> >> But about "the other game in town"...? > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > From atmer at flash.net Wed Jul 15 14:57:04 2009 From: atmer at flash.net (Anthony Stillman) Date: Tue, 14 Jul 2009 22:57:04 -0700 (PDT) Subject: [ATM] Tapping glass Message-ID: <418597.36154.qm@web82002.mail.mud.yahoo.com> Gary, Plate glass a half inch thick, 12 threads per inch, 6-ish* loose turns. The screw fit snugly when fully engaged. The glass was to see if and how it could be done. The granite is a stand. The tools are shot. At about the same time I tried to thread a glass rod. It didn't. Anthony *By -ish I mean four. From b-hamburger at artinso.com Wed Jul 15 15:07:39 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Wed, 15 Jul 2009 08:07:39 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <4A5D4671.1070404@gfphoto.com> References: <4A5BA4CC.9090806@gfphoto.com> <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> <4A5D4671.1070404@gfphoto.com> Message-ID: <015001ca0512$90403e40$b0c0bac0$@com> > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Gary Fuchs > Sent: mi?rcoles, 15 de julio de 2009 5:01 > To: Michael Coslo > Cc: ATM List > Subject: Re: [ATM] Polishing First Mirror > > I'd like to point out that it was the attitude that I objected to. And > that's something I've run across many times. I have given a legitimate answer to a legitimate question. My "attitude" was neither offensive, intimidating nor patronizing but of purely informative nature. I also think I have been long enough in the "trade" to be entitled to an opinion and I kindly request that you (Gary Fuchs) or anyone else who feels like remarking on my "attitude" should do so in private, off-list! This issue has by now moved beyond public interest and quite frankly, I am slowly starting to take exception to your (Gary Fuchs') attitude. Kindly Berthold Hamburger -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com From gfbrandenburg at yahoo.com Wed Jul 15 19:36:55 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Wed, 15 Jul 2009 03:36:55 -0700 (PDT) Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> Message-ID: <515301.13838.qm@web111502.mail.gq1.yahoo.com> Perhaps you need to do a hot press with some mesh from a bag of garlic. (remove the garlic first). This will tell you whether your lap is actually making contact all over. Often, it doesn't, and that can cause problems. Good luck. Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Wed, 7/15/09, Brad Gilbert wrote: > From: Brad Gilbert > Subject: Re: [ATM] Polishing First Mirror > To: atm at atmlist.net > Date: Wednesday, July 15, 2009, 12:16 AM > Argh! Something is broke now. > > My mirror will not polish anymore at all, the center area > looks good but the > 50%-100% zone still has tons of tiny little pits when I > shine a laser on the > surface. Also, every time I look at the Ronchigram the > surface shape didn't > change at all. > > I don't know what I'm doing wrong, I've tried TOT, MOT. > I've tried thin ceo > and thick ceo. I've tried tons of pressure and little > pressure. > > On Tue, Jul 14, 2009 at 10:01 PM, Gary Fuchs > wrote: > > > I'd like to point out that it was the attitude that I > objected to. And > > that's something I've run across many times. > > > > In one sense "Grind more, worry less" is fine advice - > when you're looking > > over someone's shoulder and see all the circumstances > and will be there to > > catch any problems. But when you're a beginner and > don't know which advice > > is appropriate to your situation or what tolerance > there is for deviation > > from that advice, then I maintain that it's better to > have more knowledge > > than less. In this case, enough to understand the > parameters of what you're > > up against at least so far as knowing what the next > couple of steps will > > bring. > > > > If the maker is capable of making a decision about > what they've been told > > here - possibly the only personalized advice they may > be receiving - then > > certainly they can handle being told how to test for > being polished out and > > that they need to get there before calling it ready to > figure. If they can't > > do that why would they follow any advice? > > > > Gary Fuchs > > > > > > > > > > Michael Coslo wrote: > > > >>
style="font-family: -moz-fixed"> > >> > >> On Jul 13, 2009, at 5:19 PM, Gary Fuchs wrote: > >> > >> > >>> I object to the notion that we should be > prevented from knowing things: > >>> by > >>> our betters and for our own good - because we > may be too weak to avoid > >>> certain temptations our betters wouldn't (or > did?) succumb to. > >>> > >> > >> Ouch! > >> > >> When I was a young Technician, a lot of > experienced people gave me a lot > >> of unwanted advice. They were not as smart as they > thought they were. I > >> though many of them were insufferable jerks. Bunch > of dummies, they were not > >> only not as smart as they thought, they spent way > too much time telling me > >> what to do and how to do it. > >> > >> After 3 or 4 years, I was amazed at how much they > had learned....... > >> > >> (with apologies to Mark Twain) > >> > >> I think there is a lot of experience talking here. > but... > >> > >> 1. most of us test before the mirror is fully > polished, especially the new > >> guys and gals. > >> > >> 2. On a first mirror, it can lead to a lot of > problems, as the new person > >> tackles two different things they don't know about > at the same time. > >> > >> 3. It's good advice, and I really doubt that > anyone is acting superior > >> here. > >> > >> I only wish that I had *not* put my first mirror > on the test stand too > >> early, which is exactly what I did. I saw things > from the back of the mirror > >> and the test stand that I ascribed to the mirror > surface. I experimented > >> with corrections, not only not actually knowing > how to make the corrections, > >> but making unneeded ones. I ended up giving myself > problems that didn't > >> exist before. > >> > >> One good thing about that is that by the time I > was finished, I had about > >> 5 mirrors worth of experience in testing and > polishing. > >> > >> There really is a lot to be said for the first > timer to avoid putting the > >> mirror on the test stand too early, unless there > is an experienced worker > >> there with them. Obviously for the more > experienced, a quick polish followed > >> by a general look see on the test stand can point > out gross problems. > >> > >> > >>> I think it's just as likely that one would be > encouraged to continue to a > >>> full polish by good test results. Or, if there > was a problem, be > >>> encouraged > >>> to take corrective action along the way. > >>> > >> > >> There are many paths of course, but the new person > doesn't necessarily > >> know the method of corrective action. I a mirror > that isn't completely > >> polished, I have to say that short of gross > problems and their corrections, > >> most corrective action? is? a bit > premature. The surface changes naturally > >> as we polish. > >> > >> That being said, it's a huge temptation to put > that mirror on the stand > >> and have at it. So admonitions against it are > largely ignored. But sometimes > >> those admonitions come from experience. I'm a bit > ambivalent about the whole > >> thing. The way I screwed up my first mirror was > tied to my premature look at > >> it, but the experience I got fixing up my mistakes > made me a better glass > >> pusher. > >> > >> > >> -73 de Mike N3LI - > >> > >> > >> > >>
> >> > >> > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From ericandroberta at sbcglobal.net Thu Jul 16 00:19:46 2009 From: ericandroberta at sbcglobal.net (D ERIC ALLEN) Date: Wed, 15 Jul 2009 08:19:46 -0700 (PDT) Subject: [ATM] Slumped blank Message-ID: <856524.6448.qm@web80503.mail.mud.yahoo.com> Sorry.? Should have given more information.? I haven't taken possession of the 20" mirror yet, and have had only a cursory look at it.? Another ATMer tested?it as slightly faster than f/4.? It appears to be pyrex, fully polished, and is 2" thick (or more). I have some experience (this will be my tenth mirror, including the 24" I just finished), just no experience?with slumped blanks. The club got the mirror blank and Clyde's Draper-type machine (very nice, but I have no room for it), but little else. >From what I gather, I won't have to grind down the back, and a more-or-less standard flotation will work.? Saves me a lot of work.? I will probably work up some sort of bowl-shaped depression for the mirror, padded and rotated to ward off astigmatism, and I should be OK. Thanks to one and all. Eric From gfbrandenburg at yahoo.com Thu Jul 16 00:48:34 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Wed, 15 Jul 2009 08:48:34 -0700 (PDT) Subject: [ATM] Slumped blank In-Reply-To: <856524.6448.qm@web80503.mail.mud.yahoo.com> Message-ID: <584118.79647.qm@web111506.mail.gq1.yahoo.com> Eric, Would you mind providing some pictures of that Draper machine, when you can? Guy Brandenburg, Washington, DC My home page on astronomy, mathematics, education: http://home.earthlink.net/~gfbranden/GFB_Home_Page.html or else http://tinyurl.com/r6fh2 ============================= "Education isn't rocket science. It's much, much harder." (Author unknown) --- On Wed, 7/15/09, D ERIC ALLEN wrote: > From: D ERIC ALLEN > Subject: Re: [ATM] Slumped blank > To: atm at atmlist.net > Date: Wednesday, July 15, 2009, 11:19 AM > Sorry.? Should have given more > information.? I haven't taken possession of the 20" mirror > yet, and have had only a cursory look at it.? Another ATMer > tested?it as slightly faster than f/4.? It appears to be > pyrex, fully polished, and is 2" thick (or more). > I have some experience (this will be my tenth mirror, > including the 24" I just finished), just no experience?with > slumped blanks. > The club got the mirror blank and Clyde's Draper-type > machine (very nice, but I have no room for it), but little > else. > >From what I gather, I won't have to grind down the > back, and a more-or-less standard flotation will work.? > Saves me a lot of work.? I will probably work up some sort > of bowl-shaped depression for the mirror, padded and rotated > to ward off astigmatism, and I should be OK. > Thanks to one and all. > Eric > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From rmay at nethere.com Thu Jul 16 05:06:52 2009 From: rmay at nethere.com (Bob May) Date: Wed, 15 Jul 2009 13:06:52 -0700 Subject: [ATM] Polishing First Mirror References: <4A5BA4CC.9090806@gfphoto.com><4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu><4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> Message-ID: <001a01ca0587$cc60cbe0$5c995545@amd> The easiest thing for a lap that doesn't seem to be working any more is to make another. Laps are something that should be made quicklly as they need to be done while the pitch is hot and finished as the pitch cools. Don't worry about any CeO that is in the pitch as this actually is a plus. Old well used pitch will actually be full of CeO and will be set with the CeO needed for polishing. You may also want to do different methods of making laps including the Dobson method. Laps often stop working because of soap getting into the organics of the pitch and keeping the pitch from holding the CeO from doing its work. In addition, too much CeO on the lap will stop the action by letting the glass roll over the pitch rather than be scraped by it. This can be fixed by a good brushing of the surface to get the excessive CeO off of the lap. I'll also note that if the mirror is moving very easy over the surface, you may just have too much water on the lap. The lap has to act like you're moving it through molassass to work. Stick and slip doesn't work. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Thu Jul 16 05:08:55 2009 From: rmay at nethere.com (Bob May) Date: Wed, 15 Jul 2009 13:08:55 -0700 Subject: [ATM] Tapping glass References: <418597.36154.qm@web82002.mail.mud.yahoo.com> Message-ID: <002301ca0588$157bb380$5c995545@amd> When things break along the way like that rod did, it is often just that the forces that you used were just too high for the material. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From masutokw at yahoo.es Thu Jul 16 06:15:49 2009 From: masutokw at yahoo.es (=?utf-8?B?w4FuZ2VsIENhcGFycsOzcw==?=) Date: Wed, 15 Jul 2009 21:15:49 +0000 (GMT) Subject: [ATM] =?utf-8?q?Picgoto_Alt-Azimutal__Beta_versi=C3=B3n=2E?= Message-ID: <882221.47653.qm@web26907.mail.ukl.yahoo.com> Hello I?m developing the alt azimutal mount driver version for this open hardware device. Software video screen capture at (better at HD full screen) http://www.youtube.com/watch?v=OVG3aeSS6kU? Moon video tracking test http://sites.google.com/site/picgoto/picgoto-alt-azimutal/picgoto-alt-az-videos Steppers? micro-step videos ?http://sites.google.com/site/picgoto/videos-1 Manual for Equatorial versi?n (atl azimutal has not been written yet) http://sites.google.com/site/picgoto/english-manual Estimated cost for components for ?Do it Yourself device? about 15? in? electronic local supplier.? From masutokw at yahoo.es Thu Jul 16 06:40:44 2009 From: masutokw at yahoo.es (=?utf-8?B?w4FuZ2VsIENhcGFycsOzcw==?=) Date: Wed, 15 Jul 2009 21:40:44 +0000 (GMT) Subject: [ATM] =?utf-8?q?Picgoto_Alt-Azimutal__Beta_versi=C3=B3n=2EBroken_?= =?utf-8?q?link?= In-Reply-To: <882221.47653.qm@web26907.mail.ukl.yahoo.com> References: <882221.47653.qm@web26907.mail.ukl.yahoo.com> Message-ID: <339373.41936.qm@web26903.mail.ukl.yahoo.com> http://www.youtube.com/watch?v=OVG3aeSS6kU ________________________________ De: ?ngel Caparr?s Para: atm at atmlist.net Enviado: mi?rcoles, 15 de julio, 2009 23:15:49 Asunto: [ATM] Picgoto Alt-Azimutal Beta versi?n. Hello I?m developing the alt azimutal mount driver version for this open hardware device. Software video screen capture at (better at HD full screen) http://www.youtube.com/watch?v=OVG3aeSS6kU? Moon video tracking test http://sites.google.com/site/picgoto/picgoto-alt-azimutal/picgoto-alt-az-videos Steppers? micro-step videos ?http://sites.google.com/site/picgoto/videos-1 Manual for Equatorial versi?n (atl azimutal has not been written yet) http://sites.google.com/site/picgoto/english-manual Estimated cost for components for ?Do it Yourself device? about 15? in? electronic local supplier.? ? ? ? _______________________________________________ ATM mailing list http://www.atmlist.net/ From burrjaw at earthlink.net Thu Jul 16 08:41:53 2009 From: burrjaw at earthlink.net (Jim Burrows) Date: Wed, 15 Jul 2009 16:41:53 -0700 Subject: [ATM] Polishing First Mirror In-Reply-To: <001a01ca0587$cc60cbe0$5c995545@amd> References: <4A5BA4CC.9090806@gfphoto.com> <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> <001a01ca0587$cc60cbe0$5c995545@amd> Message-ID: At 2009-07-15 13:06 -0700, Bob May wrote: >Laps often stop working because of soap getting into the organics >of the pitch and keeping the pitch from holding the CeO from >doing its work. In addition, too much CeO on the lap will stop >the action by letting the glass roll over the pitch rather than >be scraped by it. Also, another thing (amongst MANY) that will change the action of a lap is getting a crust which I suppose is a thin layer of pitch+polishing compound. I think the solution to this that I used was a wire brushing plus a warm press. -- Jim Burrows -- http://home.earthlink.net/~burrjaw -- mailto:burrjaw at earthlink.net -- Seattle N47.4723 W122.3662 (WGS84) From gary at gfphoto.com Thu Jul 16 10:15:21 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Wed, 15 Jul 2009 21:15:21 -0400 Subject: [ATM] Tapping glass In-Reply-To: <418597.36154.qm@web82002.mail.mud.yahoo.com> References: <418597.36154.qm@web82002.mail.mud.yahoo.com> Message-ID: <4A5E7F29.7080005@gfphoto.com> Thanks Anthony Anthony Stillman wrote: > Gary, > > Plate glass a half inch thick, 12 threads per inch, 6-ish* loose turns. The screw fit snugly when fully engaged. The glass was to see if and how it could be done. The granite is a stand. The tools are shot. > > At about the same time I tried to thread a glass rod. It didn't. > > Anthony > > > > *By -ish I mean four. > > > > From toliman at wave.co.nz Thu Jul 16 19:51:13 2009 From: toliman at wave.co.nz (Malcolm McDonald) Date: Thu, 16 Jul 2009 22:51:13 +1200 Subject: [ATM] Tapping glass References: <418597.36154.qm@web82002.mail.mud.yahoo.com> Message-ID: <56FF552FD16D44EF9F0D2251D3269C7D@Grandad> Anthony, Thanks for sharing your little experiment with us. I would never have thort it possible to tap glass. I always get the jitters whenever I drill glass. I will be giving it a go if I can find the spare time, it could be useful. I wonder what the fringe pattern would be like if you screwed a bolt into the back of a flat secondary? :-) Cheers Malcolm > Plate glass a half inch thick, 12 threads per inch, 6-ish* loose turns. > The screw fit snugly when fully engaged. The glass was to see if and how > it could be done. The granite is a stand. The tools are shot. > > At about the same time I tried to thread a glass rod. It didn't. From atm1 at hudler.org Fri Jul 17 03:27:29 2009 From: atm1 at hudler.org (atm1 at hudler.org) Date: Thu, 16 Jul 2009 13:27:29 -0500 Subject: [ATM] Tapping glass In-Reply-To: <56FF552FD16D44EF9F0D2251D3269C7D@Grandad> References: <418597.36154.qm@web82002.mail.mud.yahoo.com> <56FF552FD16D44EF9F0D2251D3269C7D@Grandad> Message-ID: <003c01ca0643$145a7b10$3d0f7130$@org> Your best bet to tapping glass is just drilling/trepan a hole and epoxy a threaded insert. This is the best method used for any mineral type material (glass, granite, concrete, epoxy granite). If you mixed in carbon fiber whiskers or chopped (200 microns) with less than 10% epoxy (stiffer than peanut butter), you'll yield a composite with a CTE comparable to that of Zerodur. The inserts should be scored on the outside. It is possible to drill an tap the epoxy composite however. I use the former method because you can minimize alignment stresses if the inserts are curing while attached to a jig or whiffle tree supports. I should point out that I've not used this on a telescope mirror (yet), but I've used this on epoxy granite, optical flats and surface plates for holding and kinematic mounting points. -Jack > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On > Behalf Of Malcolm McDonald > Sent: Thursday, July 16, 2009 5:51 AM > To: atm at atmlist.net > Subject: Re: [ATM] Tapping glass > > Anthony, Thanks for sharing your little experiment with us. I would > never > have thort it possible to tap glass. I always get the jitters whenever > I > drill glass. I will be giving it a go if I can find the spare time, it > could > be useful. > > > I wonder what the fringe pattern would be like if you screwed a bolt > into > the back of a flat secondary? :-) > > Cheers Malcolm > > > > Plate glass a half inch thick, 12 threads per inch, 6-ish* loose > turns. > > The screw fit snugly when fully engaged. The glass was to see if and > how > > it could be done. The granite is a stand. The tools are shot. > > > > At about the same time I tried to thread a glass rod. It didn't. > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From bgilb5 at gmail.com Fri Jul 17 16:34:22 2009 From: bgilb5 at gmail.com (Brad Gilbert) Date: Fri, 17 Jul 2009 02:34:22 -0500 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907170034g4d5a1785r43bfa28888913d3@mail.gmail.com> References: <4A5BA4CC.9090806@gfphoto.com> <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> <001a01ca0587$cc60cbe0$5c995545@amd> <42ee1e6c0907151751o78c158a9q4460cd617285b9f0@mail.gmail.com> <42ee1e6c0907170034g4d5a1785r43bfa28888913d3@mail.gmail.com> Message-ID: <42ee1e6c0907170034n75131533s3877c7fc8a51d59b@mail.gmail.com> ---------- Forwarded message ---------- From: Brad Gilbert Date: Fri, Jul 17, 2009 at 2:34 AM Subject: Re: [ATM] Polishing First Mirror To: Jim Burrows I have a feeling I need to go back to fine grinding :( I don't have my tool anymore. My first pitchlap broke in half so I ended up using my old tile tool. When using my 35mm eyepiece as a magnifier, and shinging a light below the mirror, there are TONs of little sparkly things everywhere. The center isn't as bad as the edge. After several hours of polishing the surface hasn't changed at all. What do I do? On Wed, Jul 15, 2009 at 7:51 PM, Brad Gilbert wrote: > Alright. I'll pick myself up a wire brush. > > Do you guys think fixing the oblate sphere would work? I'm pretty sure the > valley in the middle is the reason that part isn't getting polished because > nothing can touch it. > > Should I do W-Stroke ? I saw some pdf that had a diagram showing making > small circles in the middle and walking around the barrel but I don't know > how effective that would be. > > > On Wed, Jul 15, 2009 at 6:41 PM, Jim Burrows wrote: > >> At 2009-07-15 13:06 -0700, Bob May wrote: >> >> Laps often stop working because of soap getting into the organics >>> of the pitch and keeping the pitch from holding the CeO from >>> doing its work. In addition, too much CeO on the lap will stop >>> the action by letting the glass roll over the pitch rather than >>> be scraped by it. >>> >> >> Also, another thing (amongst MANY) that will change the action of a lap is >> getting a crust which I suppose is a thin layer of pitch+polishing compound. >> I think the solution to this that I used was a wire brushing plus a warm >> press. >> >> -- Jim Burrows >> -- http://home.earthlink.net/~burrjaw >> -- mailto:burrjaw at earthlink.net >> -- Seattle N47.4723 W122.3662 (WGS84) >> >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > > From b-hamburger at artinso.com Fri Jul 17 16:58:30 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Fri, 17 Jul 2009 09:58:30 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907170034n75131533s3877c7fc8a51d59b@mail.gmail.com> References: <4A5BA4CC.9090806@gfphoto.com> <4B72DB82-F9E0-4DE3-8A75-878F33560542@psu.edu> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> <001a01ca0587$cc60cbe0$5c995545@amd> <42ee1e6c0907151751o78c158a9q4460cd617285b9f0@mail.gmail.com> <42ee1e6c0907170034g4d5a1785r43bfa28888913d3@mail.gmail.com> <42ee1e6c0907170034n75131533s3877c7fc8a51d59b@mail.gmail.com> Message-ID: <014101ca06b4$612fc140$238f43c0$@com> Hi Brad, Considering that there were doubts about your pitch lap, I would scrape of the pitch (if possible), cast a new pitch tool and pitch lap and go back to fine grinding. In the long run you will save time instead of going on polishing for hours and hours without effect. Generally in fine grinding, once you think you ground out all pits, add another 2-3 wets of the same grit size to make sure you catch all those pits you have not detected. BTW going back to grinding happens to all of us. I am starting my current 12" for the 3rd time at 100 grit after twice getting big scratches at the very last stage of fine grinding at 9 micron. Now I had to glue on new tiles, mix new grit etc..... Consider it a ZEN exercise ;-) Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Brad Gilbert > Sent: viernes, 17 de julio de 2009 9:34 > To: atm at atmlist.net > Subject: Re: [ATM] Polishing First Mirror > > ---------- Forwarded message ---------- > From: Brad Gilbert > Date: Fri, Jul 17, 2009 at 2:34 AM > Subject: Re: [ATM] Polishing First Mirror > To: Jim Burrows > > > I have a feeling I need to go back to fine grinding :( I don't have my > tool > anymore. My first pitchlap broke in half so I ended up using my old tile > tool. > > When using my 35mm eyepiece as a magnifier, and shinging a light below > the > mirror, there are TONs of little sparkly things everywhere. The center > isn't > as bad as the edge. After several hours of polishing the surface hasn't > changed at all. > > What do I do? > > On Wed, Jul 15, 2009 at 7:51 PM, Brad Gilbert > wrote: > > > Alright. I'll pick myself up a wire brush. > > > > Do you guys think fixing the oblate sphere would work? I'm pretty sure > the > > valley in the middle is the reason that part isn't getting polished > because > > nothing can touch it. > > > > Should I do W-Stroke ? I saw some pdf that had a diagram showing > making > > small circles in the middle and walking around the barrel but I don't > know > > how effective that would be. > > > > > > On Wed, Jul 15, 2009 at 6:41 PM, Jim Burrows > wrote: > > > >> At 2009-07-15 13:06 -0700, Bob May wrote: > >> > >> Laps often stop working because of soap getting into the organics > >>> of the pitch and keeping the pitch from holding the CeO from > >>> doing its work. In addition, too much CeO on the lap will stop > >>> the action by letting the glass roll over the pitch rather than > >>> be scraped by it. > >>> > >> > >> Also, another thing (amongst MANY) that will change the action of a > lap is > >> getting a crust which I suppose is a thin layer of pitch+polishing > compound. > >> I think the solution to this that I used was a wire brushing plus a > warm > >> press. > >> > >> -- Jim Burrows > >> -- http://home.earthlink.net/~burrjaw > >> -- mailto:burrjaw at earthlink.net > >> -- Seattle N47.4723 W122.3662 (WGS84) > >> > >> > >> _______________________________________________ > >> ATM mailing list http://www.atmlist.net/ > >> > > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From bgilb5 at gmail.com Fri Jul 17 18:54:57 2009 From: bgilb5 at gmail.com (Brad Gilbert) Date: Fri, 17 Jul 2009 04:54:57 -0500 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907170245t70b2e68do47a20a35e54fb4b5@mail.gmail.com> References: <4A5BA4CC.9090806@gfphoto.com> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> <001a01ca0587$cc60cbe0$5c995545@amd> <42ee1e6c0907151751o78c158a9q4460cd617285b9f0@mail.gmail.com> <42ee1e6c0907170034g4d5a1785r43bfa28888913d3@mail.gmail.com> <42ee1e6c0907170034n75131533s3877c7fc8a51d59b@mail.gmail.com> <014101ca06b4$612fc140$238f43c0$@com> <42ee1e6c0907170245t70b2e68do47a20a35e54fb4b5@mail.gmail.com> Message-ID: <42ee1e6c0907170254q52cf415o150da8e22aac2b53@mail.gmail.com> How much will performance be affected if I decide to just polish what I can, then go on to figuring? To the naked eye none of the pits are visible. Looking through a regular light only like 3 pits per inch are visible. Under the 32mm eyepiece I would say in my field of view there are about 50 tiny pits. Some are very small and others larger. From b-hamburger at artinso.com Fri Jul 17 19:20:20 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Fri, 17 Jul 2009 12:20:20 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907170254q52cf415o150da8e22aac2b53@mail.gmail.com> References: <4A5BA4CC.9090806@gfphoto.com> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> <001a01ca0587$cc60cbe0$5c995545@amd> <42ee1e6c0907151751o78c158a9q4460cd617285b9f0@mail.gmail.com> <42ee1e6c0907170034g4d5a1785r43bfa28888913d3@mail.gmail.com> <42ee1e6c0907170034n75131533s3877c7fc8a51d59b@mail.gmail.com> <014101ca06b4$612fc140$238f43c0$@com> <42ee1e6c0907170245t70b2e68do47a20a35e54fb4b5@mail.gmail.com> <42ee1e6c0907170254q52cf415o150da8e22aac2b53@mail.gmail.com> Message-ID: <014b01ca06c8$31b14f10$9513ed30$@com> Brad, My recommendation is to go back to fine grinding. Performance of a mirror depends on so many factors (zones, smoothness etc.). However, macro surface problems like lots of pits especially around the 75-100% zones will scatter a lot of light and result in loss of contrast even though you might have polished the perfect figure. Believe me, once you get the mirror back from coating you will regret not having taken the time to get rid of all those defects. The truth is that the decision to undo your previous work with so many invested hours is never an easy one and quite frankly, I myself am suffering that misfortune myself right now. It is like turning round 100m short of summit because a thunderstorm is moving in, the thunderstorm being the equivalent to the UPS parcel with your newly aluminized and unfortunately not so shiny mirror. On the bright side, you will effectively now be grinding your second mirror with all the experience you gained from the first time. So, not only will the result be good, it will be better than the first time. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Brad Gilbert > Sent: viernes, 17 de julio de 2009 11:55 > To: atm at atmlist.net > Subject: Re: [ATM] Polishing First Mirror > > How much will performance be affected if I decide to just polish what I > can, > then go on to figuring? > > To the naked eye none of the pits are visible. Looking through a regular > light only like 3 pits per inch are visible. Under the 32mm eyepiece I > would > say in my field of view there are about 50 tiny pits. Some are very > small > and others larger. > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From b-hamburger at artinso.com Fri Jul 17 19:29:08 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Fri, 17 Jul 2009 12:29:08 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <014b01ca06c8$31b14f10$9513ed30$@com> References: <4A5BA4CC.9090806@gfphoto.com> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> <001a01ca0587$cc60cbe0$5c995545@amd> <42ee1e6c0907151751o78c158a9q4460cd617285b9f0@mail.gmail.com> <42ee1e6c0907170034g4d5a1785r43bfa28888913d3@mail.gmail.com> <42ee1e6c0907170034n75131533s3877c7fc8a51d59b@mail.gmail.com> <014101ca06b4$612fc140$238f43c0$@com> <42ee1e6c0907170245t70b2e68do47a20a35e54fb4b5@mail.gmail.com> <42ee1e6c0907170254q52cf415o150da8e22aac2b53@mail.gmail.com> <014b01ca06c8$31b14f10$9513ed30$@com> Message-ID: <014c01ca06c9$6c0831f0$441895d0$@com> I forgot to mention that you should not fall into temptation to skip grits if you return to grinding. It is better to start at 300 and work your way down quickly than finding out at 5 micron and after several hours that a few pits just won't go away. If you keep a grinding log with exact working times, you will be able to see whether time invested at respective grits is spread out fairly even, or whether there is a tendency to spend significantly more time at finer grits. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Berthold Hamburger > Sent: viernes, 17 de julio de 2009 12:20 > To: 'Brad Gilbert' > Cc: atm at atmlist.net > Subject: Re: [ATM] Polishing First Mirror > > Brad, > > My recommendation is to go back to fine grinding. > Performance of a mirror depends on so many factors (zones, smoothness > etc.). > However, macro surface problems like lots of pits especially around the > 75-100% zones will scatter a lot of light and result in loss of contrast > even though you might have polished the perfect figure. > Believe me, once you get the mirror back from coating you will regret > not > having taken the time to get rid of all those defects. > > The truth is that the decision to undo your previous work with so many > invested hours is never an easy one and quite frankly, I myself am > suffering > that misfortune myself right now. It is like turning round 100m short of > summit because a thunderstorm is moving in, the thunderstorm being the > equivalent to the UPS parcel with your newly aluminized and > unfortunately > not so shiny mirror. > > On the bright side, you will effectively now be grinding your second > mirror > with all the experience you gained from the first time. So, not only > will > the result be good, it will be better than the first time. > > Berthold > > -- > Berthold Hamburger - Cellist/Spain > Email: behambu at artinso.com > http://www.artinso.com > http://www.astro.artinso.com > > > > -----Original Message----- > > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On > Behalf > > Of Brad Gilbert > > Sent: viernes, 17 de julio de 2009 11:55 > > To: atm at atmlist.net > > Subject: Re: [ATM] Polishing First Mirror > > > > How much will performance be affected if I decide to just polish what > I > > can, > > then go on to figuring? > > > > To the naked eye none of the pits are visible. Looking through a > regular > > light only like 3 pits per inch are visible. Under the 32mm eyepiece I > > would > > say in my field of view there are about 50 tiny pits. Some are very > > small > > and others larger. > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Sat Jul 18 13:44:01 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Fri, 17 Jul 2009 21:44:01 -0700 Subject: [ATM] Polishing First Mirror In-Reply-To: <014c01ca06c9$6c0831f0$441895d0$@com> Message-ID: <212F42E2883C49538040EBEBE7952114@star7cb7aad9eb> In one of my last conversations with Tom Cave before his passing, he mentioned that he was not skipping grits. He was getting good polish ready grinds using all three of them. -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Berthold Hamburger Sent: Friday, July 17, 2009 3:29 AM To: 'Berthold Hamburger' Cc: atm at atmlist.net Subject: Re: [ATM] Polishing First Mirror I forgot to mention that you should not fall into temptation to skip grits if you return to grinding. It is better to start at 300 and work your way down quickly than finding out at 5 micron and after several hours that a few pits just won't go away. If you keep a grinding log with exact working times, you will be able to see whether time invested at respective grits is spread out fairly even, or whether there is a tendency to spend significantly more time at finer grits. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On > Behalf Of Berthold Hamburger > Sent: viernes, 17 de julio de 2009 12:20 > To: 'Brad Gilbert' > Cc: atm at atmlist.net > Subject: Re: [ATM] Polishing First Mirror > > Brad, > > My recommendation is to go back to fine grinding. > Performance of a mirror depends on so many factors (zones, smoothness > etc.). However, macro surface problems like lots of pits especially > around the 75-100% zones will scatter a lot of light and result in > loss of contrast even though you might have polished the perfect > figure. Believe me, once you get the mirror back from coating you will > regret not > having taken the time to get rid of all those defects. > > The truth is that the decision to undo your previous work with so many > invested hours is never an easy one and quite frankly, I myself am > suffering that misfortune myself right now. It is like turning round > 100m short of summit because a thunderstorm is moving in, the > thunderstorm being the equivalent to the UPS parcel with your newly > aluminized and unfortunately > not so shiny mirror. > > On the bright side, you will effectively now be grinding your second > mirror with all the experience you gained from the first time. So, not > only will > the result be good, it will be better than the first time. > > Berthold > > -- > Berthold Hamburger - Cellist/Spain > Email: behambu at artinso.com > http://www.artinso.com > http://www.astro.artinso.com > > > > -----Original Message----- > > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On > Behalf > > Of Brad Gilbert > > Sent: viernes, 17 de julio de 2009 11:55 > > To: atm at atmlist.net > > Subject: Re: [ATM] Polishing First Mirror > > > > How much will performance be affected if I decide to just polish > > what > I > > can, > > then go on to figuring? > > > > To the naked eye none of the pits are visible. Looking through a > regular > > light only like 3 pits per inch are visible. Under the 32mm eyepiece > > I would say in my field of view there are about 50 tiny pits. Some > > are very small > > and others larger. > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ _______________________________________________ ATM mailing list http://www.atmlist.net/ From b-hamburger at artinso.com Sat Jul 18 18:51:48 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Sat, 18 Jul 2009 11:51:48 +0200 Subject: [ATM] Polishing First Mirror In-Reply-To: <212F42E2883C49538040EBEBE7952114@star7cb7aad9eb> References: <014c01ca06c9$6c0831f0$441895d0$@com> <212F42E2883C49538040EBEBE7952114@star7cb7aad9eb> Message-ID: <01c201ca078d$5f5acd90$1e1068b0$@com> In machine grinding I use only 3 (with pregenerated blank). I have not tried that in hand grinding though. -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com > -----Original Message----- > From: Richard Schwartz [mailto:richard1941 at gmail.com] > Sent: s?bado, 18 de julio de 2009 6:44 > To: 'Berthold Hamburger' > Cc: atm at atmlist.net > Subject: RE: [ATM] Polishing First Mirror > > In one of my last conversations with Tom Cave before his passing, he > mentioned that he was not skipping grits. He was getting good polish > ready > grinds using all three of them. > From hermit at outofoptions.org Sat Jul 18 22:10:17 2009 From: hermit at outofoptions.org (hermit) Date: Sat, 18 Jul 2009 09:10:17 -0400 Subject: [ATM] Polishing First Mirror In-Reply-To: <42ee1e6c0907170254q52cf415o150da8e22aac2b53@mail.gmail.com> References: <4A5BA4CC.9090806@gfphoto.com> <4A5D4671.1070404@gfphoto.com> <42ee1e6c0907142116n8931107te365c83db2ca74f6@mail.gmail.com> <001a01ca0587$cc60cbe0$5c995545@amd> <42ee1e6c0907151751o78c158a9q4460cd617285b9f0@mail.gmail.com> <42ee1e6c0907170034g4d5a1785r43bfa28888913d3@mail.gmail.com> <42ee1e6c0907170034n75131533s3877c7fc8a51d59b@mail.gmail.com> <014101ca06b4$612fc140$238f43c0$@com> <42ee1e6c0907170245t70b2e68do47a20a35e54fb4b5@mail.gmail.com> <42ee1e6c0907170254q52cf415o150da8e22aac2b53@mail.gmail.com> Message-ID: <4A61C9B9.7080407@outofoptions.org> Brad Gilbert wrote: > How much will performance be affected if I decide to just polish what I can, > then go on to figuring? > > To the naked eye none of the pits are visible. Looking through a regular > light only like 3 pits per inch are visible. Under the 32mm eyepiece I would > say in my field of view there are about 50 tiny pits. Some are very small > and others larger. > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > Have you checked the figure yet? If it is worse towards the edge you may have used too long a stroke during grinding. Ken Lowther From ak666666 at hotmail.com Sat Jul 18 22:30:19 2009 From: ak666666 at hotmail.com (a) Date: Sat, 18 Jul 2009 19:30:19 +0600 Subject: [ATM] June 26 star night Message-ID: Is it ok to tell about a star gathering we had? Hassaan called members of LAST to his Raiwind Road home on Friday June 26th for a star watching event. Omer, Umair, Irfan, Behzad, Azhar, and myself gladly accepted the invitation. Shumail, Usman and a few friends of Ghazali's also joined us too. Behzad picked me up from PU new campus bridge and we rode steadily southwards. He had come on his new 125cc Honda motorcycle. We turned left from canal and went past Imran Khan's cancer hospital. We looked at a globe fitted there and thought that we were going to look at a much bigger globe that night, a globe with an almost endless size. Wapda town was on our left next and undeveloped area on our right. We saw many homes but almost no trees. All brick and concrete. It was hot. Turned left and got on Raiwind Road. Yelled and asked a bystander if it really was Raiwind road we were turning onto and he nodded. Umair reached there first. Shortly afterwards, Omer called and said he needed directions as it was his first visit from Raiwind Road side. He was on the side road with a small canal and which goes to Sharif Medical City. He couldnt see SMC yet and so wondered if he was really on the right road. Just then he spotted SMC and said he would be fine. All along I kept sending sms to Hassaan telling him of our current location. When we reached the place, Hassaan, Omer and Umair were on the roof. I asked for chilled water as the dry hot ride had left me thirsty. Hassaan's generator was being repaired. We climbed on the roof and soon were treated with chilled water and sherbet. We saw the raised flat portion of the roof where Hassaan planned to set up his observatory. We also saw that the rice sheller machine was sending thick clouds of smoke into the sky and wind was blowing this towards us. We came downstairs to wait for it to get dark. Omer had brought some printouts from heavens-above site and told us times of iridium flares. We looked for one while the sky was still somewhat bright and we missed it completely. Hassaan said that motorway or circular road would be passing just ten feet from his front door and within a year the area would be busy with traffic. Inside the house, Hassaan showed us two books on sun dials, autographed by their authors. He said he had to go to lengths to get autograph of one of the authors as he was thousand of miles away from Hassaan at the time. Shumail's friends joined us. We talked about PAS registration and Hassaan proposed a star night with IDPs. After dark, we moved out. While I used his 12x60, Hassaan's dog made an appearance. She had her long body hair cut off which made her look thin and feel cool. We went back to the roof. Hassaan said that his 12x60 needed some adjustments. Umair did it for him. Hassaan was much satisfied when he looked at the rather new moon. When I saw the moon, I was struck with a bolt of lightening. I could have toppled off the roof. I said something completely non astronomical. "I want to kiss the moon", I said. Hassaan and Umair laughed and said that my mind was occupied by something totally non astronomical and left me alone with the moon and went to join others. Soon Omer went past me with Behzad following him to collect the 8 inch scope. Omer looked at me but I was moon struck at that moment and didnt know what he was going for. Omer told us of another Iridium flare and we saw this one very well. It brightened considerably as we watch it and then faded. That was a nice experience. While Omer started assembling his scope, Azher and then Irfan joined us. Irfan had his ETX 90. Cell after cell he inserted in it. It looked like 8 pencil sized cells. A whole battery. Totalling 12 volts. Hassaan very kindly arranged for two beds and pillows for us to use binos on the milky way. Also present were a lot of things to eat and drink. Omer asked Umair to show him how to colimate his scope and the two spent half an hour doing that. We had two 7x50s and one 12x60 binoculars. I used green laser pointer and pointed out M13, coathanger, Saturn, Mel 111 and some constellations. Umair said that when he was born, Sun was in Ophiuschus(sp). Many satellites were picked up by everyone and some meteors too. Much later, I showed everyone M13, the Andromeda Galaxy. Milky Way was clearly visible. Umair said that coathanger was in a part of the milky way which had dark clouds and which made the coathanger stand out even more. Then Omer showed us many objects around the hub of the milky way. Wild duck nebula, two colliding galaxies in big dipper, Ring nebula in Lyra, Dumbell nebula, open clusters in teapot, globular clusters... It was a long list of objects. I had fun time with Behzad too and both of us worked backwards from scope finderscope view, laser pointer and then to binoculars. We picked out many objects with binos this way which the goto scope pointed at. When it was time to pack the 8 inch, I was too hasty. Probably too much caffeine made me jerky. Omer told me to be slow and carefull but my hands were quick. Hassaan took us to the dining table but we were already so full from eating on the roof that we could hardly eat anything. Around 2am, we were on road again. Behzad dropped me at Yateem Khana where I boarded a lonely van. From GPO, I walked the kilometer to Regal in the middle of the night. Omer asked me to send an sms when I reached home. I did that. Took a bath and grabbed binos instead of pillows. Omer had said something of a dolphin near cygnus and I spotted it clearly now. I went to bed with a smile on my face. a From foreilly at bestweb.net Sat Jul 18 22:44:53 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Sat, 18 Jul 2009 09:44:53 -0400 Subject: [ATM] June 26 star night References: Message-ID: <4F6B48D51DBF4E44A5C3447584792D29@D5GHLR11> You write incredobly well. Thank you for sharing this story with us. What country are you in? Francis J. O'Reilly ----- Original Message ----- From: "a" To: Sent: Saturday, July 18, 2009 9:30 AM Subject: [ATM] June 26 star night > Is it ok to tell about a star gathering we had? > > > > > Hassaan called members of LAST to his Raiwind Road home on Friday June > 26th for a star watching event. > > Omer, Umair, Irfan, Behzad, Azhar, and myself gladly accepted the > invitation. Shumail, Usman and a few friends of Ghazali's also joined us > too. > > Behzad picked me up from PU new campus bridge and we rode steadily > southwards. He had come on his new 125cc Honda motorcycle. We turned left > from canal and went past Imran Khan's cancer hospital. We looked at a > globe fitted there and thought that we were going to look at a much bigger > globe that night, a globe with an almost endless size. Wapda town was on > our left next and undeveloped area on our right. We saw many homes but > almost no trees. All brick and concrete. It was hot. Turned left and got > on Raiwind Road. Yelled and asked a bystander if it really was Raiwind > road we were turning onto and he nodded. Umair reached there first. > Shortly afterwards, Omer called and said he needed directions as it was > his first visit from Raiwind Road side. He was on the side road with a > small canal and which goes to Sharif Medical City. He couldnt see SMC yet > and so wondered if he was really on the right road. Just then he spotted > SMC and said he would be fine. All along I kept sending sms to > Hassaan telling him of our current location. > > When we reached the place, Hassaan, Omer and Umair were on the roof. I > asked for chilled water as the dry hot ride had left me thirsty. Hassaan's > generator was being repaired. We climbed on the roof and soon were treated > with chilled water and sherbet. We saw the raised flat portion of the roof > where Hassaan planned to set up his observatory. We also saw that the rice > sheller machine was sending thick clouds of smoke into the sky and wind > was blowing this towards us. We came downstairs to wait for it to get > dark. > > Omer had brought some printouts from heavens-above site and told us times > of iridium flares. We looked for one while the sky was still somewhat > bright and we missed it completely. Hassaan said that motorway or circular > road would be passing just ten feet from his front door and within a year > the area would be busy with traffic. > > Inside the house, Hassaan showed us two books on sun dials, autographed by > their authors. He said he had to go to lengths to get autograph of one of > the authors as he was thousand of miles away from Hassaan at the time. > Shumail's friends joined us. We talked about PAS registration and Hassaan > proposed a star night with IDPs. > > After dark, we moved out. While I used his 12x60, Hassaan's dog made an > appearance. She had her long body hair cut off which made her look thin > and feel cool. We went back to the roof. Hassaan said that his 12x60 > needed some adjustments. Umair did it for him. Hassaan was much satisfied > when he looked at the rather new moon. When I saw the moon, I was struck > with a bolt of lightening. I could have toppled off the roof. I said > something completely non astronomical. "I want to kiss the moon", I said. > Hassaan and Umair laughed and said that my mind was occupied by something > totally non astronomical and left me alone with the moon and went to join > others. > > Soon Omer went past me with Behzad following him to collect the 8 inch > scope. Omer looked at me but I was moon struck at that moment and didnt > know what he was going for. > > Omer told us of another Iridium flare and we saw this one very well. It > brightened considerably as we watch it and then faded. That was a nice > experience. While Omer started assembling his scope, Azher and then Irfan > joined us. Irfan had his ETX 90. Cell after cell he inserted in it. It > looked like 8 pencil sized cells. A whole battery. Totalling 12 volts. > > Hassaan very kindly arranged for two beds and pillows for us to use binos > on the milky way. Also present were a lot of things to eat and drink. > > Omer asked Umair to show him how to colimate his scope and the two spent > half an hour doing that. We had two 7x50s and one 12x60 binoculars. I used > green laser pointer and pointed out M13, coathanger, Saturn, Mel 111 and > some constellations. Umair said that when he was born, Sun was in > Ophiuschus(sp). Many satellites were picked up by everyone and some > meteors too. Much later, I showed everyone M13, the Andromeda Galaxy. > Milky Way was clearly visible. Umair said that coathanger was in a part of > the milky way which had dark clouds and which made the coathanger stand > out even more. > > Then Omer showed us many objects around the hub of the milky way. Wild > duck nebula, two colliding galaxies in big dipper, Ring nebula in Lyra, > Dumbell nebula, open clusters in teapot, globular clusters... It was a > long list of objects. I had fun time with Behzad too and both of us worked > backwards from scope finderscope view, laser pointer and then to > binoculars. We picked out many objects with binos this way which the goto > scope pointed at. > > When it was time to pack the 8 inch, I was too hasty. Probably too much > caffeine made me jerky. Omer told me to be slow and carefull but my hands > were quick. > > Hassaan took us to the dining table but we were already so full from > eating on the roof that we could hardly eat anything. > > Around 2am, we were on road again. Behzad dropped me at Yateem Khana where > I boarded a lonely van. From GPO, I walked the kilometer to Regal in the > middle of the night. Omer asked me to send an sms when I reached home. I > did that. Took a bath and grabbed binos instead of pillows. Omer had said > something of a dolphin near cygnus and I spotted it clearly now. I went to > bed with a smile on my face. > > > > > > > > > a > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From richard1941 at gmail.com Sun Jul 19 02:37:38 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Sat, 18 Jul 2009 10:37:38 -0700 Subject: [ATM] June 26 star night In-Reply-To: Message-ID: <8F89438C9E3240E0A354EAC0A8A12607@star7cb7aad9eb> What about the talk of your work at the secret atomic bomb factory, in the Religious Police Interrogation Center, and martyrdom training? If you think we don't know about that, you deserve to work in a halvah factory pounding sesame seeds all day. -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of a Sent: Saturday, July 18, 2009 6:30 AM To: atm at atmlist.net Subject: [ATM] June 26 star night Is it ok to tell about a star gathering we had? Hassaan called members of LAST to his Raiwind Road home on Friday June 26th for a star watching event. Omer, Umair, Irfan, Behzad, Azhar, and myself gladly accepted t