From fabio_falchi at yahoo.it Mon Jun 1 01:40:54 2009 From: fabio_falchi at yahoo.it (Fabio Falchi) Date: Sun, 31 May 2009 18:40:54 +0200 Subject: [ATM] 80 cm dob In-Reply-To: References: Message-ID: Dear all, after a long time since the completion of my 20" dob it is time to 'upgrade' to the next aperture. The mirror will be a 80 cm diameter, 3200 mm focal lenght. Having been not up to date for several years, I think it is wise to ask for some help in finding the best solutions. I'm now in the early deign process and these will be the goals: - portability (I need to put it on a small station wagon car) - go-to I've some ideas, such as: - lower the eyepiece height by inclining the focuser such as here: http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html - I have an Argo Navis and I'd like to use it again for the goto (should I add Stellar CAT?) - the cell should be no more complicated than a 27 points. Too much questions for a single mil? Thank you in advance! Fabio ------------------------------------------------------------------ FABIO FALCHI Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso - ISTIL Light Pollution Science and Technology Institute e-mail: falchi at lightpollution.it web: http://www.istil.it http://www.inquinamentoluminoso.it http://www.lightpollution.it/dmsp/ ------------------------------------------------------------------ From mbartels at bbastrodesigns.com Mon Jun 1 02:05:03 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sun, 31 May 2009 10:05:03 -0700 Subject: [ATM] 80 cm dob In-Reply-To: References: Message-ID: <004301c9e211$f69a5280$e3cef780$@com> >>> - lower the eyepiece height by inclining the focuser such as here: http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html <<< I've been using a simple piece of software for years to help gauge the effectiveness of lowering the eyepiece height. See http://www.bbastrodesigns.com/dnld/foldref.zip . In your case, look at the following design: folded newtonian reflector design mirror diameter? 30 focal ratio? 4 diagonal size (m.a.)? 6 focuser + tertiary flat height? 3 distance to eyepiece from primary mirror: 82 inches (2100mm) distance to diagonal from primary mirror: 96 inches (2440mm) So you can save a distance of 340 mm! >>> - I have an Argo Navis and I'd like to use it again for the goto (should I add Stellar CAT?) <<< Don't neglect the Sidereal Technology controller (I'm a reseller, so I have a vested interest here) Mel Bartels From richard1941 at gmail.com Mon Jun 1 05:28:46 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Sun, 31 May 2009 13:28:46 -0700 Subject: [ATM] 80 cm dob In-Reply-To: Message-ID: <91430CB239854F29ABCDBC502DC4B2F3@star7cb7aad9eb> You left out the requirement for perfect diffraction-limited performance and a flawless airy disk, computerized goto and closed-loop tracking, active compensation for the first six terms of the zernike polynomial, and a flexible focal plane sensor array that can utilize a variety of filters. (With the focal plane and its electronics supported by a corrector plate, powered by batteries, cooled by peltier, and communicating to the computer by blue tooth, there will be no need for diagonals or spydie vanes to impair perfect optics. Just be sure that the corrector plate transmits infrared and ultraviolent.) -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Fabio Falchi Sent: Sunday, May 31, 2009 9:41 AM To: atm at atmlist.net Subject: [ATM] 80 cm dob Dear all, after a long time since the completion of my 20" dob it is time to 'upgrade' to the next aperture. The mirror will be a 80 cm diameter, 3200 mm focal lenght. Having been not up to date for several years, I think it is wise to ask for some help in finding the best solutions. I'm now in the early deign process and these will be the goals: - portability (I need to put it on a small station wagon car) - go-to I've some ideas, such as: - lower the eyepiece height by inclining the focuser such as here: http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html - I have an Argo Navis and I'd like to use it again for the goto (should I add Stellar CAT?) - the cell should be no more complicated than a 27 points. Too much questions for a single mil? Thank you in advance! Fabio ------------------------------------------------------------------ FABIO FALCHI Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso - ISTIL Light Pollution Science and Technology Institute e-mail: falchi at lightpollution.it web: http://www.istil.it http://www.inquinamentoluminoso.it http://www.lightpollution.it/dmsp/ ------------------------------------------------------------------ _______________________________________________ ATM mailing list http://www.atmlist.net/ From foreilly at bestweb.net Mon Jun 1 09:24:52 2009 From: foreilly at bestweb.net (foreilly at bestweb.net) Date: Sun, 31 May 2009 20:24:52 -0400 (EDT) Subject: [ATM] OOPS I did it again! Another series posted today! In-Reply-To: <715797.40091.qm@web110105.mail.gq1.yahoo.com> References: <715797.40091.qm@web110105.mail.gq1.yahoo.com> Message-ID: <7227ae3db8a1a25cb5b9963435d94945.squirrel@webmail2.bestweb.net> Thanks for your kind words John, I just posted another two video set on trimming the pitch lap. It was a slow Sunday after spending yesterday at Stellafane weed wacking with some of the members who kindly allowed me to assist them. I am not as articulate as before, probably due to an illness that I recently recovered from, Hopefully the videos will get better as I resume making and posting them. Now the moon is calling me to observe. Best regards, Francis J. O'Reilly From atmer at flash.net Mon Jun 1 12:44:47 2009 From: atmer at flash.net (Anthony Stillman) Date: Sun, 31 May 2009 20:44:47 -0700 (PDT) Subject: [ATM] 80 cm dob Message-ID: <142269.15584.qm@web82001.mail.mud.yahoo.com> Richard, You forgot 100 percent reflective ultra-enhanced coatings, an off-axis design with a focal plane tilt corrector and of course putting the whole thing in orbit. Anthony Go Hubble. My favorite parts were the human parts like when they sheared off the bolt head prying off the hand rail. --- On Sun, 5/31/09, Richard Schwartz wrote: > From: Richard Schwartz > Subject: Re: [ATM] 80 cm dob > To: "'Fabio Falchi'" , atm at atmlist.net > Date: Sunday, May 31, 2009, 1:28 PM > You left out the requirement for > perfect diffraction-limited performance and > a flawless airy disk, computerized goto and closed-loop > tracking, active > compensation for the first six terms of the zernike > polynomial, and a > flexible focal plane sensor array that can utilize a > variety of filters. > (With the focal plane and its electronics supported by a > corrector plate, > powered by batteries, cooled by peltier, and communicating > to the computer > by blue tooth, there will be no need for diagonals or > spydie vanes to impair > perfect optics. Just be sure that the corrector plate > transmits infrared and > ultraviolent.) > > -----Original Message----- > From: atm-bounces at atmlist.net > [mailto:atm-bounces at atmlist.net] > On Behalf Of > Fabio Falchi > Sent: Sunday, May 31, 2009 9:41 AM > To: atm at atmlist.net > Subject: [ATM] 80 cm dob > > > Dear all, > after a long time since the completion of my 20" dob it is > time to 'upgrade' > > to the next aperture. The mirror will be a 80 cm diameter, > 3200 mm focal > lenght. > Having been not up to date for several years, I think it is > wise to ask for > some help in finding the best solutions. > I'm now in the early deign process and these will be the > goals: > - portability (I need to put it on a small station wagon > car) > - go-to > I've some ideas, such as: > - lower the eyepiece height by inclining the focuser such > as here: > http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html > - I have an Argo Navis and I'd like to use it again for the > goto (should I > add Stellar CAT?) > - the cell should be no more complicated than a 27 points. > Too much questions for a single mil? > Thank you in advance! > > Fabio > > ------------------------------------------------------------------ > FABIO FALCHI > Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso > - ISTIL Light > Pollution Science and Technology Institute > e-mail: falchi at lightpollution.it > web: http://www.istil.it > ? ???http://www.inquinamentoluminoso.it > ? ???http://www.lightpollution.it/dmsp/ > ------------------------------------------------------------------ > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From vorblesnak at peak.org Mon Jun 1 13:14:56 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Sun, 31 May 2009 21:14:56 -0700 (PDT) Subject: [ATM] Foam and Glass Mirror Report Message-ID: <45287.4.242.150.13.1243829696.squirrel@webmail.peak.org> I have been working on the 16 inch fused blank. This is a 16 inch diameter glass disk, 1/4 inch thick, fused to standard glass foam 2 inches thick. It is a salvage from an earlier failed fusing experiment. The original diameter was 22 inches. It has some significant edge failure from the kiln cycle but I think I can get a 13 inch disk out of it. I have not touched it in a month or so but finally got a day where I could go play in the shop. To bring myself back up to speed on where the grind was I took the time to run a series of sagitta measurements across the mirror on different diameters. The curve was pretty good, the center of the curve is about 1/4 inch to the right of true center. I marked all of the results on the glass with a sharpie marker. Looks like a 66 inch focal length, more or less. I noticed the foam had a wedge shape to it. I laid the blank face down and used a board covered with sand paper to remove the wedge. The foam is soft stuff, took about 5 minutes to true up the thickness. I put it on the grinding machine and used one of my old carbo grinding wheels as a tool. I charged it with 220 grit in the center hole, splashed some water on the glass and started the machine. One hour later the mud had a dirty cream color to it and after rinsing the surface was smooth and clean, no sharpie marks left. At least in the center 13 inches. I switch to an old diamond lapidary wheel, charged the surface with 320 and ran a 30 minute wet. No pits jumped out at me when I tested so I switched to 25 micron and did two 45 minute wets. Now I could see one little scratch area and some pits in the outer 20% of the surface. Back to 320 or carry on? Since the machine is doing the work I just kept up the 25 micron wets using the diamond wheel for a tool. About 5 hours of machine time later this thing is almost polished. No pits revealed by the light anyway. Tomorrow after work I will do the pitch lap and see if I can do a couple of polishing cycles. I am working on the big kiln. I was going to size it for a 60 inch but I have no glass that big so I sized it for the 48. I got the muffle ring done and got the frame for the ceramic wool done. I have to get the tool cast and work it a bit. I hope to slump some glass by mid June. I got some borosilicate glass foam and ran a small test for fuse and slump properties. I am hoping it will not fail under heat as badly as the soda lime foam does. What is going on with the other pucks I sent out into the world? David Davis Toledo, OR 97391 From atmer at flash.net Mon Jun 1 15:05:44 2009 From: atmer at flash.net (Anthony Stillman) Date: Sun, 31 May 2009 23:05:44 -0700 (PDT) Subject: [ATM] 80 cm dob Message-ID: <295922.66458.qm@web82005.mail.mud.yahoo.com> Fabio, Realistically: An enhanced coating on the secondary is a good idea. The cost of such a coating on the primary I think makes its value questionable. Inclining the focus is a mixed bag. To shorten the assembly significantly the tilt off square must be large. The typical thirty degrees shortens the mirror to focuser distance about 10 percent at the cost of a larger secondary and an extended baffle. I'm not dismissing the design, it's what I have in mind for my light bucket. Assuming I every do anything more than draw pretty pictures in POV. Depending on how thick your primary will be a 27 point mirror mount may be enough. Check out PLOT. My blank is 20:1 and 27 points works for it. As you make your design decisions please post them and your rationale. Anthony From fabio_falchi at yahoo.it Mon Jun 1 16:23:14 2009 From: fabio_falchi at yahoo.it (Fabio Falchi) Date: Mon, 1 Jun 2009 09:23:14 +0200 Subject: [ATM] 80 cm dob In-Reply-To: <91430CB239854F29ABCDBC502DC4B2F3@star7cb7aad9eb> References: <91430CB239854F29ABCDBC502DC4B2F3@star7cb7aad9eb> Message-ID: <261C5836467341089B6132A07B123EC8@PCStudio> Richard, you're correct. I left out adaptive optics, but it seems that none (yes, I'm simplyfing) is working to put that technology down to Earth for amateurs. CCDs went from professionals to amateurs in less than ten years, AO no. For AO I don't intend a simple tilt/shift plane mirror, I intend a rubber mirror that allow your eye to see diffraction limited images with your 20" or 30". A 1500x diffraction limited view of Saturn or Jupiter will be beyond imagination. I simply asked for a series of links where some other amateurs showed telescopes meeting the requirements. Clear skies, Fabio ----- Original Message ----- From: "Richard Schwartz" To: "'Fabio Falchi'" ; <> Sent: Sunday, May 31, 2009 10:28 PM Subject: RE: [ATM] 80 cm dob You left out the requirement for perfect diffraction-limited performance and a flawless airy disk, computerized goto and closed-loop tracking, active compensation for the first six terms of the zernike polynomial, and a flexible focal plane sensor array that can utilize a variety of filters. (With the focal plane and its electronics supported by a corrector plate, powered by batteries, cooled by peltier, and communicating to the computer by blue tooth, there will be no need for diagonals or spydie vanes to impair perfect optics. Just be sure that the corrector plate transmits infrared and ultraviolent.) -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Fabio Falchi Sent: Sunday, May 31, 2009 9:41 AM To: atm at atmlist.net Subject: [ATM] 80 cm dob Dear all, after a long time since the completion of my 20" dob it is time to 'upgrade' to the next aperture. The mirror will be a 80 cm diameter, 3200 mm focal lenght. Having been not up to date for several years, I think it is wise to ask for some help in finding the best solutions. I'm now in the early deign process and these will be the goals: - portability (I need to put it on a small station wagon car) - go-to I've some ideas, such as: - lower the eyepiece height by inclining the focuser such as here: http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html - I have an Argo Navis and I'd like to use it again for the goto (should I add Stellar CAT?) - the cell should be no more complicated than a 27 points. Too much questions for a single mil? Thank you in advance! Fabio ------------------------------------------------------------------ FABIO FALCHI Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso - ISTIL Light Pollution Science and Technology Institute e-mail: falchi at lightpollution.it web: http://www.istil.it http://www.inquinamentoluminoso.it http://www.lightpollution.it/dmsp/ ------------------------------------------------------------------ _______________________________________________ ATM mailing list http://www.atmlist.net/ From robert.houdart at cruxis.be Mon Jun 1 18:33:59 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 1 Jun 2009 11:33:59 +0200 Subject: [ATM] 80 cm dob In-Reply-To: Message-ID: Fabio, You may find the following pages useful for getting some ideas or choosing a particular design: - Stellafane: http://stellafane.org/misc/links.html - Astrosurf: http://www.astrosurf.com/altaz/index_e.htm For the mirror cell, depending on the mirror thickness even an 18-point cell can be OK. Use PLOP to validate your configuration. For the mirror edge support check the Mirror Edge Support Calculator. Clear skies, Robert > -----Original Message----- > > Dear all, > after a long time since the completion of my 20" dob it is > time to 'upgrade' > to the next aperture. The mirror will be a 80 cm diameter, > 3200 mm focal > lenght. > Having been not up to date for several years, I think it is > wise to ask for > some help in finding the best solutions. > I'm now in the early deign process and these will be the goals: > - portability (I need to put it on a small station wagon car) > - go-to > I've some ideas, such as: > - lower the eyepiece height by inclining the focuser such as here: > http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html > - I have an Argo Navis and I'd like to use it again for the > goto (should I > add Stellar CAT?) > - the cell should be no more complicated than a 27 points. > Too much questions for a single mil? > Thank you in advance! > > Fabio From atmer at flash.net Mon Jun 1 18:53:20 2009 From: atmer at flash.net (Anthony Stillman) Date: Mon, 1 Jun 2009 02:53:20 -0700 (PDT) Subject: [ATM] 80 cm dob Message-ID: <572173.39582.qm@web82003.mail.mud.yahoo.com> ...I intend a rubber mirror Detailed articles describing wavefront sensory systems, feedback mechanisms, and deformation technology have appeared in the optical literature ("Applied Optics", "Optical Engineering",...). There's an article, if I remember right, in a British Journal uhhh... "Measurement Science and Technology" that describes a bending mechanism's feedback instrumentality. It must have been the '90s, maybe late 80's. The wavefront deformation mechanism was depicted but not well described. I have this glimmer of a memory that they were using a 6502. There are some papers and a book that puts it all together, notable is "Adaptive Optics for Astronomical Telescopes" by "John W. Hardy" It's not a how to manual but with a broad skill base (NERD!) there's enough in the book to get something started. Anthony From fabio_falchi at yahoo.it Mon Jun 1 18:55:28 2009 From: fabio_falchi at yahoo.it (Fabio Falchi) Date: Mon, 1 Jun 2009 11:55:28 +0200 Subject: [ATM] 80 cm dob In-Reply-To: <91430CB239854F29ABCDBC502DC4B2F3@star7cb7aad9eb> References: <91430CB239854F29ABCDBC502DC4B2F3@star7cb7aad9eb> Message-ID: <800B1EF8D4984060B9379E404EA6072D@PCStudio> Anthony, I'll surely go with enahanced coating on the secondary. I forgot the thickness of the 800 mm mirror: 38 mm at the border. But, even with this so low profile a 18 points cell will work, as it seems using PLOP. Sling or glue? Thank you Robert, for the links. I'll explore them. Clear and once dark skies, Fabio From rflrs at verizon.net Mon Jun 1 19:29:14 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Mon, 01 Jun 2009 06:29:14 -0400 Subject: [ATM] 80 cm dob In-Reply-To: References: Message-ID: <4A23AD7A.5090203@verizon.net> Robert Houdart wrote: > Fabio, > > You may find the following pages useful for getting some ideas or choosing a > particular design: > > - Stellafane: http://stellafane.org/misc/links.html I wonder if they are aware of just how many of those links are simply typed incorrectly... From robert.houdart at cruxis.be Mon Jun 1 20:34:51 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 1 Jun 2009 13:34:51 +0200 Subject: [ATM] 80 cm dob In-Reply-To: <800B1EF8D4984060B9379E404EA6072D@PCStudio> Message-ID: Fabio, > I forgot the thickness of the 800 mm mirror: 38 mm at the > border. But, even with this so low profile a 18 points > cell will work, as it seems using PLOP. Indeed, for a 800x38 mm f/4 configuration PLOP gives an RMS error of about 7 nm - not perfect but quite acceptable. > Sling or glue? The Mirror Edge Support Calculator at http://www.cruxis.com/scope/mirroredgecalculator.htm gives the following results: - 180? cable sling: RMS error 8.8 nm - glued on an 18-point cell: RMS error 138 nm In other words, glueing would produce severe astigmatism. I'd recommend using a 180? cable sling or a 45? whiffle tree design. Cheers, Robert http://www.cruxis.com/scope/scope1100.htm From rsackett00 at yahoo.com Mon Jun 1 21:14:47 2009 From: rsackett00 at yahoo.com (Ross Sackett) Date: Mon, 1 Jun 2009 05:14:47 -0700 (PDT) Subject: [ATM] Foam and Glass Mirror Report Message-ID: <970160.13449.qm@web59204.mail.re1.yahoo.com> David, Interesting experiments. Did you fuse disks to both sides of the glass, or just the optical surface? I was just wondering if sandwich construction might have stiffness and expansion advantages, and perhaps make it easier to mount without crushing the glass foam. I saw Bob May carrying something similar to what you describe at RTMC--one of yours? Ross --- On Sun, 5/31/09, vorblesnak at peak.org wrote: > From: vorblesnak at peak.org > Subject: [ATM] Foam and Glass Mirror Report > To: atm at atmlist.net > Date: Sunday, May 31, 2009, 11:14 PM > I have been working on the 16 inch > fused blank. This is a 16 inch diameter > glass disk, 1/4 inch thick, fused to standard glass foam 2 > inches thick. > It is a salvage from an earlier failed fusing experiment. > The original > diameter was 22 inches. It has some significant edge > failure from the kiln > cycle but I think I can get a 13 inch disk out of it. I > have not touched > it in a month or so but finally got a day where I could go > play in the > shop. > > To bring myself back up to speed on where the grind was I > took the time to > run a series of sagitta measurements across the mirror on > different > diameters. The curve was pretty good, the center of the > curve is about 1/4 > inch to the right of true center. I marked all of the > results on the glass > with a sharpie marker. Looks like a 66 inch focal length, > more or less. I > noticed the foam had a wedge shape to it. I laid the blank > face down and > used a board covered with sand paper to remove the wedge. > The foam is soft > stuff, took about 5 minutes to true up the thickness. > > I put it on the grinding machine and used one of my old > carbo grinding > wheels as a tool. I charged it with 220 grit in the center > hole, splashed > some water on the glass and started the machine. One hour > later the mud > had a dirty cream color to it and after rinsing the surface > was smooth and > clean, no sharpie marks left. At least in the center 13 > inches. > > I switch to an old diamond lapidary wheel, charged the > surface with 320 > and ran a 30 minute wet. No pits jumped out at me when I > tested so I > switched to 25 micron and did two 45 minute wets. Now I > could see one > little scratch area and some pits in the outer 20% of the > surface. Back to > 320 or carry on? Since the machine is doing the work I just > kept up the 25 > micron wets using the diamond wheel for a tool. About 5 > hours of machine > time later this thing is almost polished. No pits revealed > by the light > anyway. Tomorrow after work I will do the pitch lap and see > if I can do a > couple of polishing cycles. > > I am working on the big kiln. I was going to size it for a > 60 inch but I > have no glass that big so I sized it for the 48. I got the > muffle ring > done and got the frame for the ceramic wool done. I have to > get the tool > cast and work it a bit. I hope to slump some glass by mid > June. > > I got some borosilicate glass foam and ran a small test for > fuse and slump > properties. I am hoping it will not fail under heat as > badly as the soda > lime foam does. > > What is going on with the other pucks I sent out into the > world? > > David Davis > Toledo, OR 97391 > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From richard at foucault.co.uk Mon Jun 1 21:42:06 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Mon, 1 Jun 2009 13:42:06 +0100 Subject: [ATM] 80 cm dob In-Reply-To: References: <800B1EF8D4984060B9379E404EA6072D@PCStudio> Message-ID: <1907553234.20090601134206@foucault.co.uk> Hello Robert, Monday, June 1, 2009, 12:34:51 PM, you wrote: > In other words, glueing would produce severe astigmatism. I'd recommend > using a 180? cable sling or a 45? whiffle tree design. Glued with what?. Sintered glass to metal or 5mm of high compliance silicone rubber ? -- Best regards, Richard in the UK From robert.houdart at cruxis.be Mon Jun 1 23:24:17 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 1 Jun 2009 16:24:17 +0200 Subject: [ATM] 80 cm dob In-Reply-To: <1907553234.20090601134206@foucault.co.uk> Message-ID: Richard, > Glued with what?. Sintered glass to metal or 5mm of high compliance > silicone rubber ? We're talking about a mirror glued on a standard 18-point cell with, for example, 18 blobs of silicone (or any other equivalent method). The astigmatism problem comes from the the offset of the lateral forces with respect to the center of gravity (COG) of the mirror. This offset generates a global bending moment on the mirror which results in astigmatism. On professional telescopes with large, glued mirrors one usually finds push-pull devices on the back that compensate locally for the eccentricity of the lateral force with respect to the COG. In the standard mirror cells for amateur telescopes this is not the case, and to prevent the global bending the lateral forces need to be applied at the COG of the mirror. Gluing the mirror's back will only work well for mirrors up to about 15 inch. Regards, Robert http://www.cruxis.com/scope/mirroredgecalculator.htm From dlwebb at canit.se Tue Jun 2 01:52:00 2009 From: dlwebb at canit.se (Dominic-Luc Webb) Date: Mon, 1 Jun 2009 18:52:00 +0200 (MET DST) Subject: [ATM] silvering success Message-ID: I now spent some efffort on the silvering process. I used considerably more dilute silver nitrate than described: http://www.atmsite.org/contrib/Coslo/silver/ That article apparently used pure anhydrous silver nitrate. Stock solution worked out to be 0.5 M. Final volume would be 4 times more, so 0.125 M. What was available to me was 0.1 M stock. I compensated by using very concentrated NaOH and sugar. I heated the final mix in presence of the microscope slides I wanted partially silvered. Goal is 50:50 beam splitter. First effort was a bit too lightly silvered, but expect to hit target today or tomorrow. I will be improving the chemical preparation and then post some details. First impression is that this goes for simple tasks like making a rudimentary beam splitter. Dominic From rmay at nethere.com Tue Jun 2 05:18:55 2009 From: rmay at nethere.com (Bob May) Date: Mon, 1 Jun 2009 13:18:55 -0700 Subject: [ATM] 80 cm dob References: <4A23AD7A.5090203@verizon.net> Message-ID: <001501c9e2f6$338ed280$dd985545@amd> The problem with a number of the sites is that the owners think that putting out the info is something that only needs to be done for a few weeks and don't realize that links to their site are left behind in a lot of other pages. Info put on the web for stuff like what we are looking for i.e. telescope making and so forth, is info that should never go away, going away being put somewhere other than where it first got put. My list of optical and astronomy stuff now has a lot of broken links due to people pulling down their info from the web. A lot of good stuff that just doesn't exist anymore. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From hermit at outofoptions.org Tue Jun 2 05:21:10 2009 From: hermit at outofoptions.org (hermit) Date: Mon, 01 Jun 2009 16:21:10 -0400 Subject: [ATM] 80 cm dob In-Reply-To: <001501c9e2f6$338ed280$dd985545@amd> References: <4A23AD7A.5090203@verizon.net> <001501c9e2f6$338ed280$dd985545@amd> Message-ID: <4A243836.6030903@outofoptions.org> Bob May wrote: > The problem with a number of the sites is that the owners think > that putting out the info is something that only needs to be done > for a few weeks and don't realize that links to their site are > left behind in a lot of other pages. Info put on the web for > stuff like what we are looking for i.e. telescope making and so > forth, is info that should never go away, going away being put > somewhere other than where it first got put. > My list of optical and astronomy stuff now has a lot of broken > links due to people pulling down their info from the web. A lot > of good stuff that just doesn't exist anymore. > Bob May > > The purpose of http://atmsite.org was to archive stuff people didn't want to maintain but is useful. Ken Lowther From smithersscope at yahoo.com Tue Jun 2 06:08:12 2009 From: smithersscope at yahoo.com (Dave Smith) Date: Mon, 1 Jun 2009 14:08:12 -0700 (PDT) Subject: [ATM] 80 cm dob Message-ID: <451877.88107.qm@web51811.mail.re2.yahoo.com> Hi, Correct me if I'm wrong, but don't dual supports positioned (laterally) at 90 degrees to the edge of the mirror--the method endorsed by Mel in his tridob--compensate for or null out most" of these forces? While they may not compensate perfectly, they are easy for the amateur to adapt and employ. I know Jan van Gastel and I have both had good success incorporating these into our tri-dobs. Can/would others like to comment? Dave --- On Mon, 6/1/09, Robert Houdart wrote: From: Robert Houdart Subject: Re: [ATM] 80 cm dob To: "'ATM List'" Date: Monday, June 1, 2009, 7:24 AM Richard, > Glued with what?. Sintered glass to metal or 5mm of high compliance > silicone rubber ? We're talking about a mirror glued on a standard 18-point cell with, for example, 18 blobs of silicone (or any other equivalent method). The astigmatism problem comes from the the offset of the lateral forces with respect to the center of gravity (COG) of the mirror. This offset generates a global bending moment on the mirror which results in astigmatism. On professional telescopes with large, glued mirrors one usually finds push-pull devices on the back that compensate locally for the eccentricity of the lateral force with respect to the COG. In the standard mirror cells for amateur telescopes this is not the case, and to prevent the global bending the lateral forces need to be applied at the COG of the mirror. Gluing the mirror's back will only work well for mirrors up to about 15 inch. Regards, Robert http://www.cruxis.com/scope/mirroredgecalculator.htm _______________________________________________ ATM mailing list http://www.atmlist.net/ From robert.houdart at cruxis.be Tue Jun 2 06:43:44 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Mon, 1 Jun 2009 23:43:44 +0200 Subject: [ATM] 80 cm dob In-Reply-To: <451877.88107.qm@web51811.mail.re2.yahoo.com> Message-ID: Dave, > Correct me if I'm wrong, but don't dual supports positioned > (laterally) at 90 degrees to the edge of the mirror--the > method endorsed by Mel in his tridob--compensate for or null > out most" of these forces? > While they may not compensate perfectly, they are easy for > the amateur to adapt and employ. I know Jan van Gastel and I > have both had good success incorporating these into our > tri-dobs. Can/would others like to comment? You're absolutely correct, 90? edge bearings are another good solution if they operate at the center of gravity of the mirror (the same big "if" applies to the 180? cable sling and the 45? whiffletree solutions). See the Mirror Edge Support Calculator at http://www.cruxis.com/scope/mirroredgecalculator.htm where you'll find more details and where you can analyze the different configurations for your own telescope. Cheers, Robert From stainless_steel at suddenlink.net Tue Jun 2 07:37:18 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Mon, 1 Jun 2009 17:37:18 -0500 Subject: [ATM] ATM: Slighly off-topic, I apologize. Message-ID: <00E5F4B0A2FB4FD5A91DBFDA8F77C73B@R101> Well, they were bluffing. They cannnot find out who I am, nor where I am. Evidently I can still use "Outlook Express", my beloved, very expressive (HTML) email program. What a bunch of idiot they are. What an idiot I am; now I have to plough through about 70 emails. I look forward to it, my brothers. (Are there no "sisters" on this email forum?) DLZ-130 From woodycxd at comcast.net Tue Jun 2 09:24:53 2009 From: woodycxd at comcast.net (Wayne Hilliard) Date: Mon, 1 Jun 2009 20:24:53 -0400 Subject: [ATM] Question for James Lerch Message-ID: Sorry to spam the list with this email but I can not find James Lerch's email. Anyone know his email? I want/need to query him about his nearfieldsim and nearfieldsim2 programs. Thanks for your indulgence Wayne Hilliard From atmer at flash.net Tue Jun 2 09:58:33 2009 From: atmer at flash.net (Anthony Stillman) Date: Mon, 1 Jun 2009 17:58:33 -0700 (PDT) Subject: [ATM] 80 cm dob Message-ID: <469608.98024.qm@web82006.mail.mud.yahoo.com> ...90 degrees to the edge of the (optic)... In the professional world this is the approach most often taken when mounting optics vertically. It's cost effective, easy to implement, and it works well. Granted, amateurs often know better than professions (the value of not have to make a living off optics) but in this case I think the pros have it. Anthony From vorblesnak at peak.org Wed Jun 3 02:09:10 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Tue, 2 Jun 2009 10:09:10 -0700 (PDT) Subject: [ATM] Foam and Glass Mirror Report Message-ID: <52906.159.121.96.200.1243962550.squirrel@webmail.peak.org> Some more notes on the glass and foam blank. I made a pitch lap for the blank last night. I used an old 12 inch tool that I had on the shelf. Medium hard pitch, kind of a blend of odds and ends from various tools. As usual I did not catch the pitch at the right moment and the center got quite hard. It looked like I had contact but after and hour of polishing the center was virtually untouched. I cold pressed and went to bed. If necessary I will warm the lap in a bit of hot water and repress for contact. I just admitted to practicing repression. You will have the decency to ignore that right?? I did a quick check of the polished areas on the disk with my old ronchi tester and I have lines, nice regular ones too. One source of discussion has been if the fused blank would have tension and cause astigmatism. Evidently not. David Davis Toledo, OR 97391 From stainless_steel at suddenlink.net Wed Jun 3 06:10:29 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 2 Jun 2009 16:10:29 -0500 Subject: [ATM] ATM: Re: "Repression." Message-ID: David, All you needed to do was respell "repression": re-pression. Otherwise, you are really one of the best okay guys I know, and a good telescope maker, and a darned good windmill man (so I have been told). DLZ-130 From al at sgi.com Wed Jun 3 22:12:22 2009 From: al at sgi.com (Alexis Cousein) Date: Wed, 03 Jun 2009 15:12:22 +0200 Subject: [ATM] ATM: Re: "Repression." In-Reply-To: References: Message-ID: <4A2676B6.6050805@sgi.com> stainless_steel at suddenlink.net wrote: > David, > > All you needed to do was respell "repression": re-pression. From stainless_steel at suddenlink.net Thu Jun 4 02:04:33 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 3 Jun 2009 12:04:33 -0500 Subject: [ATM] ATM: Re: "Repression." In-Reply-To: <4A2676B6.6050805@sgi.com> References: <4A2676B6.6050805@sgi.com> Message-ID: <4EE64BFD165641998676BF81307094FE@R101> Fellow glass pushers, all: Sounds like it could escalate into a Homeland Security issue thing. Telescope mirrors might be a threat, somehow, to the well being of our great sovereign nation. I will look into it thoroughly and report, in due course. Thank you for bringing this more serious thing, aspect of the whole subject, to my attention. I will investigate and report. Agent: DLZ-130 ----- Original Message ----- From: "Alexis Cousein" To: Cc: ; "ATM list" Sent: Wednesday, June 03, 2009 8:12 AM Subject: Re: [ATM] ATM: Re: "Repression." > stainless_steel at suddenlink.net wrote: >> David, >> >> All you needed to do was respell "repression": re-pression. > > Come and see the violence inherent in the system!" while being > manhandled> > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.52/2152 - Release Date: 06/03/09 05:53:00 From vorblesnak at peak.org Thu Jun 4 03:02:59 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Wed, 3 Jun 2009 11:02:59 -0700 (PDT) Subject: [ATM] Large primary mirrors Message-ID: <4318.69.59.200.230.1244052179.squirrel@webmail.peak.org> I understand that there was a discussion on this a while back under the topic of "Tessellated Primaries for Big Dobs". I have an idea for this. Instead of working with active control, why not a monolithic structure. Form a block of glass foam to the appropriate size, say 65 inches diameter by 18 inches thick. This could be assembled from a number of standard pieces glued together. Mill the rough curve into it. Now cover that milled surface with a tessellation of glass plate and work the resulting surface as a single mirror. No need for active control, the foam has sufficient thickness and density for the blank. I recently worked and broke a 60 inch tabletop that was 1/2 inch thick. The size and the weight made it almost impossible to handle. A monolithic foam block is lighter than the 60 inch tabletop. The glass tessellation pieces could be 3/8ths plate cut to 12 inch hexagonals. Given a 60 inch f3 primary the ROC would be 720 inches. Sagitta would be 1.25 inches. BUT! the sagitta on each piece would only be about 0.05 inches. 3/8ths plate will stand on its own across 12 inches. To further help with the assembly of the block the glass could be preslumped to the ROC prior to mounting. David Davis Toledo, OR 97391 From blaktony86 at yahoo.com Thu Jun 4 03:30:03 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Wed, 3 Jun 2009 11:30:03 -0700 (PDT) Subject: [ATM] Large primary mirrors Message-ID: <575854.24405.qm@web81908.mail.mud.yahoo.com> I was thinking this a few weeks ago but in a smaller scale. I thought of using hexagonal glass tiles on a plaster tool with the curve generated in the plaster. Then the glass tiles could be epoxied onto the surface. I am sure foam glass would work better because of the thermal properties are the same as glass. ? My idea was crushed when I found out how different the rates of thermal expansion were of epoxy, plaster, and glass. I then gave up on the idea. ? Your approach is defintley much more doable. What is the density of foam glass BTW? Is it available to the public? ? -Tony --- On Wed, 6/3/09, vorblesnak at peak.org wrote: From: vorblesnak at peak.org Subject: [ATM] Large primary mirrors To: atm at atmlist.net Date: Wednesday, June 3, 2009, 1:02 PM I understand that there was a discussion on this a while back under the topic of "Tessellated Primaries for Big Dobs". I have an idea for this. Instead of working with active control, why not a monolithic structure. Form a block of glass foam to the appropriate size, say 65 inches diameter by 18 inches thick. This could be assembled from a number of standard pieces glued together. Mill the rough curve into it. Now cover that milled surface with a tessellation of glass plate and work the resulting surface as a single mirror. No need for active control, the foam has sufficient thickness and density for the blank. I recently worked and broke a 60 inch tabletop that was 1/2 inch thick. The size and the weight made it almost impossible to handle. A monolithic foam block is lighter than the 60 inch tabletop. The glass tessellation pieces could be 3/8ths plate cut to 12 inch hexagonals. Given a 60 inch f3 primary the ROC would be 720 inches. Sagitta would be 1.25 inches. BUT! the sagitta on each piece would only be about 0.05 inches. 3/8ths plate will stand on its own across 12 inches. To further help with the assembly of the block the glass could be preslumped to the ROC prior to mounting. David Davis Toledo, OR 97391 _______________________________________________ ATM mailing list http://www.atmlist.net/ From holmmarkd at gmail.com Thu Jun 4 10:11:46 2009 From: holmmarkd at gmail.com (Mark Holm) Date: Wed, 03 Jun 2009 21:11:46 -0400 Subject: [ATM] ATM: Re: "Repression." In-Reply-To: <4A2676B6.6050805@sgi.com> References: <4A2676B6.6050805@sgi.com> Message-ID: <4A271F52.8080303@gmail.com> No one expects the Spanish Inquisition! Alexis Cousein wrote: > > Come and see the violence inherent in the system!" while being > manhandled> > -- Mark Holm markholm at verizon.net holmmarkd at gmail.com From foreilly at verizon.net Thu Jun 4 12:17:47 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Wed, 03 Jun 2009 23:17:47 -0400 Subject: [ATM] Keeping in contact Message-ID: <0C53E70E6162469BA350458C94420F05@HELENYLCMWAV95> In order to keep my lap in good contact with my work when I am away from my work, in this case a seven inch (Don't ask) flat, I put the pitch lap on the Parker barrel, put wet it with water, put two pieces of wax paper over the lap and put the piece on top. I then cover the entire thing with a wet towel. It works like a charm and the wax paper will leave an impression in the lap which is somewhat akin to microfacets. For those who don't know, YOUNGSTERS, Wax paper is something your mother would have wrapped your lunch sandwich in before the days of Saran wrap. Francis J. O'Reilly From blaktony86 at yahoo.com Thu Jun 4 12:33:27 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Wed, 3 Jun 2009 20:33:27 -0700 (PDT) Subject: [ATM] Keeping in contact Message-ID: <172378.49147.qm@web81901.mail.mud.yahoo.com> Thats funny because I was about to make the same post on this topic. I also use wax paper between the pitch and mirror and it never sticks and always remains in good contact with each other. And the ripples it makes in the pitch is like micro-faceting that seems to last about an hour of polishing. Good stuff. I use a single sheet of wax paper and have the tool slightly wet to get the wax paper to wrinkle which puts the impression in the pitch. -Tony --- On Wed, 6/3/09, Francis J. O'Reilly wrote: From: Francis J. O'Reilly Subject: [ATM] Keeping in contact To: atm at atmlist.net Cc: "Allen Hall" , "Dick Parker" , drewclan at aol.com Date: Wednesday, June 3, 2009, 10:17 PM In order to keep my lap in good contact with my work when I am away from my work, in this case a seven inch (Don't ask) flat, I put the pitch lap on the Parker barrel, put wet it with water, put two pieces of wax paper over the lap and put the piece on top. I then cover the entire thing with a wet towel. It works like a charm and the wax paper will leave an impression in the lap which is somewhat akin to microfacets. For those who don't know, YOUNGSTERS, Wax paper is something your mother would have wrapped your lunch sandwich in before the days of Saran wrap. Francis J. O'Reilly _______________________________________________ ATM mailing list http://www.atmlist.net/ From atmer at flash.net Thu Jun 4 12:55:19 2009 From: atmer at flash.net (Anthony Stillman) Date: Wed, 3 Jun 2009 20:55:19 -0700 (PDT) Subject: [ATM] Keeping in contact Message-ID: <96843.60728.qm@web82001.mail.mud.yahoo.com> Wax paper, Saran wrap, aluminum foil are all fine if you're leaving it for a while, but it's no good when figuring or even I think when you're actively working it. No more than a day-ish between sessions. Then the advantage of close contact outweighs the the hassle of a sticky separation. Anthony From vorblesnak at peak.org Thu Jun 4 13:12:07 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Wed, 3 Jun 2009 21:12:07 -0700 (PDT) Subject: [ATM] Large Primary Mirrors Message-ID: <41686.69.59.210.100.1244088727.squirrel@webmail.peak.org> The glass foam is readily available from a good insulation contractor. I found it at a store in Eugene Oregon. If you do a google search on FoamGlass they have a store locater on the product web site. Richard Schwartz brings up a good point. The foam is an insulation, how will that affect cool down? I have no answer. It could be a problem but maybe not. A covered mirror box would isolate the mirror from the environment. It certainly would not pick up any heat from below. Another question was raised about the durability of the foam block. It is very soft and prone to environmental damage. Ed DeMarco polished one into non existence in about the blink of an eye. I think the whole puck would have to set in a pan and the pan would take the environmental hit. David Davis Toledo, OR 97391 >I was thinking this a few weeks ago but in a smaller scale. I thought of >using hexagonal glass tiles on a plaster tool with the curve generated in >plaster. Then the glass tiles could be epoxied onto the surface. I am sure >foam glass would work better because of the thermal properties are the same >as glass. >My idea was crushed when I found out how different the rates of thermal >expansion were of epoxy, plaster, and glass. I then gave up on the idea. >Your approach is defintley much more doable. What is the density of foam >glass BTW? Is it available to the public? >-Tony From camkit at mweb.co.za Thu Jun 4 17:06:13 2009 From: camkit at mweb.co.za (chris forder) Date: Thu, 04 Jun 2009 10:06:13 +0200 Subject: [ATM] 80 cm dob Message-ID: <4A278075.5060003@mweb.co.za> Has the notion of hanging as opposed to slinging a large morror be cosidered? The mirror would be hung from the top as opposed to slung from the bottom. This would replace the weight astigmatism resulting from compression with a weight hanging astiigmatism due to stretching? One could test the results on the foucault or interferometer testes. Chris Cape Town From robert.houdart at cruxis.be Thu Jun 4 17:59:55 2009 From: robert.houdart at cruxis.be (Robert Houdart) Date: Thu, 4 Jun 2009 10:59:55 +0200 Subject: [ATM] 80 cm dob In-Reply-To: <4A278075.5060003@mweb.co.za> Message-ID: Chris, > Has the notion of hanging as opposed to slinging a large > morror be cosidered? > The mirror would be hung from the top as opposed to slung > from the bottom. > This would replace the weight astigmatism resulting from > compression with a weight hanging astiigmatism due to > stretching? Mauro Da Lio has run a couple of analyses for hung mirrors some time ago. See http://autocostruttori.blogspot.com/2007/11/unusual-ways-of-lateral-restrain ing.html A possible good solution is to hang the mirror using two radial wires at +-45? from vertical. This would create exactly the same configuration as the 90? edge bearings solution at the bottom, if you manage to attach the wires on the edge of the mirror at the level of its center of gravity. Cheers, Robert *Mirror Edge Support Calculator* http://www.cruxis.com/scope/mirroredgecalculator.htm From stainless_steel at suddenlink.net Fri Jun 5 00:52:26 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 4 Jun 2009 10:52:26 -0500 Subject: [ATM] Large Primary Mirrors In-Reply-To: <41686.69.59.210.100.1244088727.squirrel@webmail.peak.org> References: <41686.69.59.210.100.1244088727.squirrel@webmail.peak.org> Message-ID: Environmental? Environmental? Do you want to attract the further attention of Homeland Security to our dangerous hobby? And the mere mention of Dr. R. S., the fomenter of revolutions! My recommendation is to use a low profile vocabulary. And look at me: a dissertation last week on RFNA and UDMH- the very stuff they use to...... better watch my dancing fingers, and my rattling brain. I hope they don't come for me....they will put me in a cell with Flying Wing Man aka Dr. R. S., the guy who slumps glass and gets away with it (sometimes). Agent DLZ-130 ----- Original Message ----- From: To: Sent: Wednesday, June 03, 2009 11:12 PM Subject: [ATM] Large Primary Mirrors > The glass foam is readily available from a good insulation contractor. I > found it at a store in Eugene Oregon. If you do a google search on > FoamGlass they have a store locater on the product web site. > > Richard Schwartz brings up a good point. The foam is an insulation, how > will that affect cool down? I have no answer. It could be a problem but > maybe not. A covered mirror box would isolate the mirror from the > environment. It certainly would not pick up any heat from below. > > Another question was raised about the durability of the foam block. It is > very soft and prone to environmental damage. Ed DeMarco polished one into > non existence in about the blink of an eye. I think the whole puck would > have to set in a pan and the pan would take the environmental hit. > > David Davis > Toledo, OR 97391 > >>I was thinking this a few weeks ago but in a smaller scale. I thought of >>using hexagonal glass tiles on a plaster tool with the curve generated in >>plaster. Then the glass tiles could be epoxied onto the surface. I am sure >>foam glass would work better because of the thermal properties are the >>same >>as glass. > > >>My idea was crushed when I found out how different the rates of thermal >>expansion were of epoxy, plaster, and glass. I then gave up on the idea. > > >>Your approach is defintley much more doable. What is the density of foam >>glass BTW? Is it available to the public? > > >>-Tony > > > > _______________________________________________ > 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: 270.12.53/2154 - Release Date: 06/04/09 05:53:00 From rmay at nethere.com Fri Jun 5 06:17:41 2009 From: rmay at nethere.com (Bob May) Date: Thu, 4 Jun 2009 14:17:41 -0700 Subject: [ATM] 80 cm dob References: <4A278075.5060003@mweb.co.za> Message-ID: <001001c9e559$e7500180$62995545@amd> The problem of haning a mirror is getting it to do so wihtout stressing the glass at a point spot. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From vorblesnak at peak.org Fri Jun 5 08:57:10 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Thu, 4 Jun 2009 16:57:10 -0700 (PDT) Subject: [ATM] Tessellated Blank, Picture Message-ID: <2429.69.59.200.230.1244159830.squirrel@webmail.peak.org> 18 inch F3. the hexagons are really very crudely cut. They are based on a wooden pattern 3 inches in diameter. I used Permatex Ultra Black Silicone for the adhesive. It takes a day or two to cure. Then I will cast a tool and grind. http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/Tessellated%20Blank.JPG The glass is the scrap from the foam and puck blanks I sent out. David Davis Toledo, OR 97391 From foreilly at verizon.net Fri Jun 5 10:08:18 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Thu, 04 Jun 2009 21:08:18 -0400 Subject: [ATM] Polishing Compound Message-ID: I recently purchased five kg of #85 Rare Earth Polishing Compound from Universal Photonics in Long Island. I just polished out a seven inch flat in two and a half hours by hand using the compound. I'm no speed demon, but I appreciate getting things done quickly. This stuff is amazing. While five kg is pretty much more than any average atm would use in several lifetimes, It might be a worthwhile purchase for a club. Francis J. O'Reilly From wa4guu at verizon.net Fri Jun 5 12:10:53 2009 From: wa4guu at verizon.net (Jerry) Date: Thu, 04 Jun 2009 23:10:53 -0400 Subject: [ATM] Istanbul Kultur Universitesi (Istanbul Culture University) ATM workshop and Astronomy Symposium Message-ID: <07E5A7683A194B368C0063ABC1075A49@D85SJB21> I have been invited, and will participate in an ATM workshop in Turkey. The workshop is sponsored by Istanbul Kultur Universitesi (Istanbul Culture University) July 4 through July 9. The workshop will be held at Solar-Beach in Kilyos, north of Istanbul on the Black Sea coast. On July 9, following the workshop I will attend an astronomy symposium in Istanbul at the university. I will give a short talk on testing and figuring ala Texereau. And then on July 10 there will be a "Star Fest" held at Solar-Beach. I'm sure many of the telescopes made in the workshop will see first light here. The workshop is very well planned for one hundred participants. We will make 6" f:7 mirrors and build a kit telescope designed by the workshop's organizing ATMs. It is as near a certainty as can be that each participant will leave with a working telescope. Amateur telescope making is relatively new to Turkey. One intention of the workshop is to spread many ATM telescopes far and wide across the country so that many people are exposed to telescope making and astronomy. Some of those become the optical and astronomy professionals of the future. From pictures and correspondence, what I have seen of their planning, preparation, and skill, they will do an excellent job of that. After this workshop there will be 100 more ATM telescopes in Turkey. When I leave to come home there will be 99 of them left in Turkey. :-) http://fen-edebiyat2.iku.edu.tr/aas2009/ I will give a report when I return from Istanbul. Jerry From foreilly at verizon.net Fri Jun 5 12:32:27 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Thu, 04 Jun 2009 23:32:27 -0400 Subject: [ATM] Polishing Compound References: <37CD4A41-A797-4819-BB97-32298F3EFB26@verizon.net> Message-ID: <8BAA7B26FBB44AE98F3B6707F79680F7@HELENYLCMWAV95> Hi Don, No sleeks, scraatches or other problems from the Polishing liquid. I was using Gugolz 55 pitch. I never use pads. I ground down to three micron Aluminum Oxide which I also bought from Universal Photonics (Five pound quantity) Francis J. O'Reilly ----- Original Message ----- From: "Don Surles" To: "Francis J. O'Reilly" Sent: Thursday, June 04, 2009 9:40 PM Subject: Re: [ATM] Polishing Compound > would this rare earth be Barnsite? fwiw...we have tried many diff > mediums over the years and have settled on CeOx from Salem Dist...we have > had no sleeks or scratches that i am aware of ...some of the rouges, > barnsites, other brands of CeOx seemed to have a minimal level of > "contaminants" that did result in sleeks/scratches. > > for 9 years we have been using Salem products and have been very > fortunate with them. > > did you use pads or pitch? > > Don... > > > On Jun 4, 2009, at 9:08 PM, Francis J. O'Reilly wrote: > >> I recently purchased five kg of #85 Rare Earth Polishing Compound from >> Universal Photonics in Long Island. >> >> I just polished out a seven inch flat in two and a half hours by hand >> using the compound. I'm no speed demon, but I appreciate getting things >> done quickly. This stuff is amazing. While five kg is pretty much more >> than any average atm would use in several lifetimes, It might be a >> worthwhile purchase for a club. >> >> Francis J. O'Reilly >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > > From mick at liquidgold.eclipse.co.uk Fri Jun 5 12:34:34 2009 From: mick at liquidgold.eclipse.co.uk (Mick Dunn) Date: Fri, 5 Jun 2009 04:34:34 +0100 Subject: [ATM] Polishing Compound References: Message-ID: Interesting Just had a look on there site but couldn't find it. How much did you pay for the 5kg. Mick ----- Original Message ----- From: Francis J. O'Reilly To: atm at atmlist.net ; Mirror-O-Matic at yahoogroups.com ; schiefbuilders at yahoogroups.com Sent: Friday, June 05, 2009 2:08 AM Subject: [ATM] Polishing Compound I recently purchased five kg of #85 Rare Earth Polishing Compound from Universal Photonics in Long Island. I just polished out a seven inch flat in two and a half hours by hand using the compound. I'm no speed demon, but I appreciate getting things done quickly. This stuff is amazing. While five kg is pretty much more than any average atm would use in several lifetimes, It might be a worthwhile purchase for a club. Francis J. O'Reilly _______________________________________________ ATM mailing list http://www.atmlist.net/ __________ NOD32 4132 (20090604) Information __________ This message was checked by NOD32 antivirus system. http://www.eset.com From foreilly at verizon.net Fri Jun 5 12:53:39 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Thu, 04 Jun 2009 23:53:39 -0400 Subject: [ATM] Polishing Compound References: Message-ID: I don't remember but it wasn't too bad. I bought some Aluminum Oxide (Large quantity) and Gugolz Pitch as well. It all came to the hundered dollar range ----- Original Message ----- From: "Mick Dunn" To: Sent: Thursday, June 04, 2009 11:34 PM Subject: Re: [ATM] Polishing Compound > Interesting > Just had a look on there site but couldn't find it. > How much did you pay for the 5kg. > > Mick > ----- Original Message ----- > From: Francis J. O'Reilly > To: atm at atmlist.net ; Mirror-O-Matic at yahoogroups.com ; > schiefbuilders at yahoogroups.com > Sent: Friday, June 05, 2009 2:08 AM > Subject: [ATM] Polishing Compound > > > I recently purchased five kg of #85 Rare Earth Polishing Compound from > Universal Photonics in Long Island. > > I just polished out a seven inch flat in two and a half hours by hand > using the compound. I'm no speed demon, but I appreciate getting things > done quickly. This stuff is amazing. While five kg is pretty much more > than any average atm would use in several lifetimes, It might be a > worthwhile purchase for a club. > > Francis J. O'Reilly > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > __________ NOD32 4132 (20090604) Information __________ > > This message was checked by NOD32 antivirus system. > http://www.eset.com > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From lutfu_cakmak at yahoo.com Fri Jun 5 19:51:09 2009 From: lutfu_cakmak at yahoo.com (lutfu_cakmak at yahoo.com) Date: Fri, 5 Jun 2009 03:51:09 -0700 (PDT) Subject: [ATM] Istanbul Kultur Universitesi (Istanbul Culture University) ATM workshop and Astronomy Symposium Message-ID: <135469.33029.qm@web50711.mail.re2.yahoo.com> We are atm_turk yahoo group proud for inviting Jerry to our atm workshop? in Istanbul. This is a second workshop, first was in 2007 and Haldun Menali (ATMoB, AAVSO ) and Dick Parker participated. I found out lot of thing from Jerry and this list and made 3 mirrors (8" f6,5 - 10" f7 - 15" f4,9) and 2 telescopes. Thanks a lot to all. Despite of site language turkish but you can see pictures some of part 6" f7 workshop telescope; http://atmturk.org/index.php/3_boyutlu_model_ve_ilgili_dosyalar http://atmturk.org/index.php/Giri%C5%9F http://atmturk.org/index.php/Kundak_Montaj%C4%B1 http://atmturk.org/index.php/Y%C3%BCkseklik_%C3%87emberlerinin_Montaj%C4%B1 http://atmturk.org/index.php/Ba%C4%9Flama_elemanlar%C4%B1_%28vida%2C_somun%2C_pul%2C_..%29_ve_montaj_i%C3%A7in_gereken_aletler All the best, Lutfu Cakmak ? --- On Thu, 6/4/09, Jerry wrote: > From: Jerry > Subject: [ATM] Istanbul Kultur Universitesi (Istanbul Culture University) ATM workshop and Astronomy Symposium > To: "ATM list" , atm_free at yahoogroups.com > Date: Thursday, June 4, 2009, 8:10 PM > I have been invited, and will > participate in an ATM workshop in Turkey. The > workshop is sponsored by Istanbul Kultur Universitesi > (Istanbul Culture > University) July 4 through July 9. The workshop will be > held at Solar-Beach > in Kilyos, north of Istanbul on the Black Sea coast. > > On July 9, following the workshop I will attend an > astronomy symposium in > Istanbul at the university. I will give a short talk on > testing and figuring > ala Texereau. > > And then on July 10 there will be a "Star Fest" held at > Solar-Beach. I'm > sure many of the telescopes made in the workshop will see > first light here. > > The workshop is very well planned for one hundred > participants. We will make > 6" f:7 mirrors and build a kit telescope designed by the > workshop's > organizing ATMs. It is as near a certainty as can be that > each participant > will leave with a working telescope. > > Amateur telescope making is relatively new to Turkey. One > intention of the > workshop is to spread many ATM telescopes far and wide > across the country so > that many people are exposed to telescope making and > astronomy. Some of > those become the optical and astronomy professionals of the > future. From > pictures and correspondence, what I have seen of their > planning, > preparation, and skill, they will do an excellent job of > that. After this > workshop there will be 100 more ATM telescopes in Turkey. > When I leave to > come home there will be 99 of them left in Turkey. :-) > > http://fen-edebiyat2.iku.edu.tr/aas2009/ > > I will give a report when I return from Istanbul. > > Jerry > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From blaktony86 at yahoo.com Fri Jun 5 22:23:09 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Fri, 5 Jun 2009 06:23:09 -0700 (PDT) Subject: [ATM] Tessellated Blank, Picture Message-ID: <273611.31217.qm@web81903.mail.mud.yahoo.com> An issue I just thought of is dont you think that the silicone you used to hold the hex-glass on the glass foam will be too elastic? For example if you are grinding and polishing on that then the silicone will "give" and perhaps distort the figure? Would it not be better to fuse the glass or perhaps find an adhesive that has no elastic properties and therefore is rigid? Then again, it might be hard to find an adhesive with similar thermal properties (coefficient of expansion) as glass. ? -Tony --- On Thu, 6/4/09, vorblesnak at peak.org wrote: From: vorblesnak at peak.org Subject: RE: [ATM] Tessellated Blank, Picture To: "TONY B" Date: Thursday, June 4, 2009, 10:46 PM The foam is extremely soft. I created the curve just like I do the curve in glass. Hog and smooth. I use a small ring to hog and then and old small tool to smooth it all out. Check with a sphereometer or by doing zone measurements. It takes about 5 minutes to do a curve. Andrew generates the curves with a pendulum router. Take a piece of rigid something, a tube, or pipe or rod a dowel and hang a router from it. The length to the tip of the grinding head should be the ROC,or twice the focal length. I set one up using a piece of plastic pipe and battery powered hand drill duct taped to it. For the bit I used a small hole saw wrapped with sand paper. You should try one. It is always good to have many hands working an idea. Regardless of the outcome. David Davis Toledo, OR 97391 >???Thats awesome!! Is that foam glass its on? How did u get the curve > generated?? Thats a neat experiment that i would like to try. > -----Original Message----- > Date: Thursday, June 04, 2009 7:00:28 pm > To: atm at atmlist.net > From: vorblesnak at peak.org > Subject: [ATM] Tessellated Blank, Picture > > 18 inch F3. the hexagons are really very crudely cut. They are based on a > wooden pattern 3 inches in diameter. I used Permatex Ultra Black Silicone > for the adhesive. It takes a day or two to cure. Then I will cast a tool > and grind. > > http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/Tessellated%20Blank.JPG > > The glass is the scrap from the foam and puck blanks I sent out. > > David Davis > Toledo, OR 97391 > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > > From vorblesnak at peak.org Fri Jun 5 23:44:23 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Fri, 5 Jun 2009 07:44:23 -0700 (PDT) Subject: [ATM] Tessellated Blank, Picture In-Reply-To: <273611.31217.qm@web81903.mail.mud.yahoo.com> References: <273611.31217.qm@web81903.mail.mud.yahoo.com> Message-ID: <2843.69.59.200.230.1244213063.squirrel@webmail.peak.org> Good questions! Good observations! In defense the layer of silicone is very thin and the outer edges of the glass are more or less resting on the foam. I was more worried about the polishing friction peeling the glass off of the foam. One of the reasons I began to look at this process is the cost in time and materials to build a kiln that will handle 1 meter and larger blanks. Then handling that glass, getting it into and out of the kiln. Then working on it. Last June there was some discussion on the list about the Mt Wilson telescopes and issues Ritchie had in handling that glass. The 60 inch blank I had was to much for me to move solo. Dan Bakken tells me he had to have help while moving and working the blank that became Hercules. Big scopes become club projects, and that is fine, but there is still a lot of tooling up. That is what I am learning. You could certainly fuse the glass to the foam. It is a matter of heat control and sizing the product to get a finished piece. But where would you get the kiln? A small kiln is pretty cheap to run and you could make a common size hexagon of glass and foam and scale up a mirror. There has been some testing on adhesives on foam. I didn't do it but I got told about it. Hard stuff, like epoxies and other resin glues bond well but are showing a tendency to separate over time. It appears that the resin contracts to the point that it shatters the top layer of foam and falls off. We are still exploring glue. I had some good results with Gorilla glue. And in fact that is the glue I used on the small foam and glass pucks I sent out the various grinders. Bob May is working his by hand and has not reported problems. I worked a couple of them on a Hindle grinding machine with no problems. Ed DeMarco had a catastrophic failure of his blank and had reported that he thought the glue bond was failing. Andrew thinks Mill Bond is a good answer. You should experiment. You might discover the best answer. David Davis Toledo, OR 97391 > An issue I just thought of is dont you think that the silicone you used to > hold the hex-glass on the glass foam will be too elastic? For example if > you are grinding and polishing on that then the silicone will "give" and > perhaps distort the figure? Would it not be better to fuse the glass or > perhaps find an adhesive that has no elastic properties and therefore is > rigid? Then again, it might be hard to find an adhesive with similar > thermal properties (coefficient of expansion) as glass. > ? > -Tony > > --- On Thu, 6/4/09, vorblesnak at peak.org wrote: > > > From: vorblesnak at peak.org > Subject: RE: [ATM] Tessellated Blank, Picture > To: "TONY B" > Date: Thursday, June 4, 2009, 10:46 PM > > > The foam is extremely soft. I created the curve just like I do the curve > in glass. Hog and smooth. I use a small ring to hog and then and old small > tool to smooth it all out. Check with a sphereometer or by doing zone > measurements. It takes about 5 minutes to do a curve. Andrew generates the > curves with a pendulum router. Take a piece of rigid something, a tube, or > pipe or rod a dowel and hang a router from it. The length to the tip of > the grinding head should be the ROC,or twice the focal length. I set one > up using a piece of plastic pipe and battery powered hand drill duct taped > to it. For the bit I used a small hole saw wrapped with sand paper. > > You should try one. It is always good to have many hands working an idea. > Regardless of the outcome. > > David Davis > Toledo, OR 97391 > >>???Thats awesome!! Is that foam glass its on? How did u get the curve >> generated?? Thats a neat experiment that i would like to try. >> -----Original Message----- >> Date: Thursday, June 04, 2009 7:00:28 pm >> To: atm at atmlist.net >> From: vorblesnak at peak.org >> Subject: [ATM] Tessellated Blank, Picture >> >> 18 inch F3. the hexagons are really very crudely cut. They are based on >> a >> wooden pattern 3 inches in diameter. I used Permatex Ultra Black >> Silicone >> for the adhesive. It takes a day or two to cure. Then I will cast a tool >> and grind. >> >> http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/Tessellated%20Blank.JPG >> >> The glass is the scrap from the foam and puck blanks I sent out. >> >> David Davis >> Toledo, OR 97391 >> >> >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> >> >> > > > > > From stainless_steel at suddenlink.net Sat Jun 6 05:30:05 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Fri, 5 Jun 2009 15:30:05 -0500 Subject: [ATM] Large Primary Mirrors In-Reply-To: <2866.69.59.200.230.1244213767.squirrel@webmail.peak.org> References: <41686.69.59.210.100.1244088727.squirrel@webmail.peak.org> <2866.69.59.200.230.1244213767.squirrel@webmail.peak.org> Message-ID: Yes, David, I did start the discussion, and I believe (if my memory serves me, which it isn't lately) Jerry started the thread. Everyone said: "IMPOSSIBLE". As for Richard, I was sure that over the years, he was my friend. He will not answer any emails from me. Hold his opinions, if they refer to me, in confidence. I am sorry that I have obviously lost his friendship. DLZ-130 P.S.- I consider this forum democratic. I do not believe, now, that a tessellated large instrument is possible (for amateurs- to construct). My "friendship" nickname for Richard was (is) "Flying Wing Man" because, in his employment with Northrop, he flew some of the pioneering flying wing prototypes. He is an accomplished sailplane pilot, as I am an accomplished pilot of low wing tailwheel airplanes. I guess he decided we have nothing in common, anymore. I have no chip on my shoulder, and would welcome an opinion from someone as to why Richard will not answer any of my emails. My humour, below, is an attempt at Richard's kind of humour. Not so good, compared to the "Wing Man" (he said he never flew the N9M) ----- Original Message ----- From: To: Sent: Friday, June 05, 2009 9:56 AM Subject: Re: [ATM] Large Primary Mirrors > So, you started this whole tessellated discussion last June, if I am to > believe the archives. Other than the bit of tongue in cheek below I have > not heard your opinion. Would you care to weigh in on the merits or lack > there of? The evil Dr. R S gave me his two cents. I will hold it in > confidence if that is important. > > David Davis > Toledo, OR 97391 > >> >> Environmental? Environmental? >> >> Do you want to attract the further attention of Homeland Security to our >> dangerous hobby? And the mere mention of Dr. R. S., the fomenter of >> revolutions! >> >> My recommendation is to use a low profile vocabulary. And look at me: a >> dissertation last week on RFNA and UDMH- the very stuff they use to...... >> better watch my dancing fingers, and my rattling brain. I hope they don't >> come for me....they will put me in a cell with Flying Wing Man aka Dr. R. >> S., the guy who slumps glass and gets away with it (sometimes). >> >> Agent DLZ-130 >> >> ----- Original Message ----- > > > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.53/2156 - Release Date: 06/05/09 06:24:00 From vorblesnak at peak.org Sat Jun 6 05:53:11 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Fri, 5 Jun 2009 13:53:11 -0700 (PDT) Subject: [ATM] Large Primary Mirrors In-Reply-To: References: <41686.69.59.210.100.1244088727.squirrel@webmail.peak.org> <2866.69.59.200.230.1244213767.squirrel@webmail.peak.org> Message-ID: <3575.69.59.200.230.1244235191.squirrel@webmail.peak.org> Well, I am working the 18 inch prototype. I have 40 wets of 220 grit into it and have about 80% contact at this point. Mechanically it is quite good. The devil will be in the figure but that is a week or so away. Lots of work to do and lots of failure opportunities ahead. David Davis Toledo, OR 97391 > Yes, David, > > I did start the discussion, and I believe (if my memory serves me, which > it > isn't lately) Jerry started the thread. Everyone said: "IMPOSSIBLE". As > for > Richard, I was sure that over the years, he was my friend. He will not > answer any emails from me. Hold his opinions, if they refer to me, in > confidence. I am sorry that I have obviously lost his friendship. > > DLZ-130 > > P.S.- I consider this forum democratic. I do not believe, now, that a > tessellated large instrument is possible (for amateurs- to construct). My > "friendship" nickname for Richard was (is) "Flying Wing Man" because, in > his > employment with Northrop, he flew some of the pioneering flying wing > prototypes. He is an accomplished sailplane pilot, as I am an accomplished > pilot of low wing tailwheel airplanes. I guess he decided we have nothing > in > common, anymore. I have no chip on my shoulder, and would welcome an > opinion > from someone as to why Richard will not answer any of my emails. > > My humour, below, is an attempt at Richard's kind of humour. Not so good, > compared to the "Wing Man" (he said he never flew the N9M) > > > ----- Original Message ----- > From: > To: > Sent: Friday, June 05, 2009 9:56 AM > Subject: Re: [ATM] Large Primary Mirrors > > >> So, you started this whole tessellated discussion last June, if I am to >> believe the archives. Other than the bit of tongue in cheek below I have >> not heard your opinion. Would you care to weigh in on the merits or lack >> there of? The evil Dr. R S gave me his two cents. I will hold it in >> confidence if that is important. >> >> David Davis >> Toledo, OR 97391 >> >>> >>> Environmental? Environmental? >>> >>> Do you want to attract the further attention of Homeland Security to >>> our >>> dangerous hobby? And the mere mention of Dr. R. S., the fomenter of >>> revolutions! >>> >>> My recommendation is to use a low profile vocabulary. And look at me: a >>> dissertation last week on RFNA and UDMH- the very stuff they use >>> to...... >>> better watch my dancing fingers, and my rattling brain. I hope they >>> don't >>> come for me....they will put me in a cell with Flying Wing Man aka Dr. >>> R. >>> S., the guy who slumps glass and gets away with it (sometimes). >>> >>> Agent DLZ-130 >>> >>> ----- Original Message ----- >> >> >> >> > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.339 / Virus Database: 270.12.53/2156 - Release Date: 06/05/09 > 06:24:00 > > From richard1941 at gmail.com Sat Jun 6 19:00:47 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Sat, 6 Jun 2009 03:00:47 -0700 Subject: [ATM] 80 cm dob In-Reply-To: References: Message-ID: <2644EF7E-002A-4ACE-8CE1-3980E622162D@gmail.com> Why not 19 points? He does not seem to want a hole in his mirror. Also my ability to respond to e-mail is temporarily impaired (but not totally eliminated) as I am on the road from Los Angeles to Albany New Yokk. Sent from my iPhone On Jun 1, 2009, at 2:33, "Robert Houdart" wrote: > Fabio, > > You may find the following pages useful for getting some ideas or > choosing a > particular design: > > - Stellafane: http://stellafane.org/misc/links.html > - Astrosurf: http://www.astrosurf.com/altaz/index_e.htm > > For the mirror cell, depending on the mirror thickness even an 18- > point cell > can be OK. Use PLOP to validate your configuration. For the mirror > edge > support check the Mirror Edge Support Calculator. > > Clear skies, > Robert > > >> -----Original Message----- >> >> Dear all, >> after a long time since the completion of my 20" dob it is >> time to 'upgrade' >> to the next aperture. The mirror will be a 80 cm diameter, >> 3200 mm focal >> lenght. >> Having been not up to date for several years, I think it is >> wise to ask for >> some help in finding the best solutions. >> I'm now in the early deign process and these will be the goals: >> - portability (I need to put it on a small station wagon car) >> - go-to >> I've some ideas, such as: >> - lower the eyepiece height by inclining the focuser such as here: >> http://www.biophysik.uni-freiburg.de/Reiner/ATM/atm_e.html >> - I have an Argo Navis and I'd like to use it again for the >> goto (should I >> add Stellar CAT?) >> - the cell should be no more complicated than a 27 points. >> Too much questions for a single mil? >> Thank you in advance! >> >> Fabio > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From ntent at pctcnet.net Sat Jun 6 23:04:41 2009 From: ntent at pctcnet.net (ntent) Date: Sat, 06 Jun 2009 09:04:41 -0500 Subject: [ATM] 1.25" Eyepieces Message-ID: <4A2A7779.2090407@pctcnet.net> Has anyone had any experience with Zhumell brand eyepieces? From blaktony86 at yahoo.com Sat Jun 6 23:35:12 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Sat, 6 Jun 2009 07:35:12 -0700 (PDT) Subject: [ATM] Ronchi images and figuring help Message-ID: <730685.70810.qm@web81908.mail.mud.yahoo.com> Hello, I am deciding whether to parabolize my mirror now or try and make a perfect sphere with a perfect edge first. I have been combating TDE for a few weeks now. The ronchi image of the TDE before was pretty bad, the edges hooked severly. I also had a bad central hole. After completing my modified Mirror-o-Matic grinding and polishing machine, I polished for a few hours trying various methods to knock down the TDE. I know have a very smooth even figure with which appears to be a rolled edge. It matches closely to the computer generated ronchi images. I would like to call upon the ATM gurus knowledge and expertise to lead me to whether I should continue spherizing and try to get that perfect edge, or to go ahead and continue on to parabolization. View my ronchi images here: http://blaktony86.fortunecity.com/ronchitesting.html Thanks for the help guys, -Tony From stainless_steel at suddenlink.net Sun Jun 7 00:51:40 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Sat, 6 Jun 2009 10:51:40 -0500 Subject: [ATM] Large Primary Mirrors In-Reply-To: <3575.69.59.200.230.1244235191.squirrel@webmail.peak.org> References: <41686.69.59.210.100.1244088727.squirrel@webmail.peak.org> <2866.69.59.200.230.1244213767.squirrel@webmail.peak.org> <3575.69.59.200.230.1244235191.squirrel@webmail.peak.org> Message-ID: <1FD03002A1DF4B84BF36E146629F9977@R101> When the time comes, David, Hire an excorcist to finish the figuring, and get that devil out!!! D-LZ130 ----- Original Message ----- From: To: Cc: "ATM list" ; Sent: Friday, June 05, 2009 3:53 PM Subject: Re: [ATM] Large Primary Mirrors > Well, I am working the 18 inch prototype. I have 40 wets of 220 grit into > it and have about 80% contact at this point. Mechanically it is quite > good. The devil will be in the figure but that is a week or so away. Lots > of work to do and lots of failure opportunities ahead. > > David Davis > Toledo, OR 97391 > >> Yes, David, >> >> I did start the discussion, and I believe (if my memory serves me, which >> it >> isn't lately) Jerry started the thread. Everyone said: "IMPOSSIBLE". As >> for >> Richard, I was sure that over the years, he was my friend. He will not >> answer any emails from me. Hold his opinions, if they refer to me, in >> confidence. I am sorry that I have obviously lost his friendship. >> >> DLZ-130 >> >> P.S.- I consider this forum democratic. I do not believe, now, that a >> tessellated large instrument is possible (for amateurs- to construct). My >> "friendship" nickname for Richard was (is) "Flying Wing Man" because, in >> his >> employment with Northrop, he flew some of the pioneering flying wing >> prototypes. He is an accomplished sailplane pilot, as I am an >> accomplished >> pilot of low wing tailwheel airplanes. I guess he decided we have nothing >> in >> common, anymore. I have no chip on my shoulder, and would welcome an >> opinion >> from someone as to why Richard will not answer any of my emails. >> >> My humour, below, is an attempt at Richard's kind of humour. Not so good, >> compared to the "Wing Man" (he said he never flew the N9M) >> >> >> ----- Original Message ----- >> From: >> To: >> Sent: Friday, June 05, 2009 9:56 AM >> Subject: Re: [ATM] Large Primary Mirrors >> >> >>> So, you started this whole tessellated discussion last June, if I am to >>> believe the archives. Other than the bit of tongue in cheek below I have >>> not heard your opinion. Would you care to weigh in on the merits or lack >>> there of? The evil Dr. R S gave me his two cents. I will hold it in >>> confidence if that is important. >>> >>> David Davis >>> Toledo, OR 97391 >>> >>>> >>>> Environmental? Environmental? >>>> >>>> Do you want to attract the further attention of Homeland Security to >>>> our >>>> dangerous hobby? And the mere mention of Dr. R. S., the fomenter of >>>> revolutions! >>>> >>>> My recommendation is to use a low profile vocabulary. And look at me: a >>>> dissertation last week on RFNA and UDMH- the very stuff they use >>>> to...... >>>> better watch my dancing fingers, and my rattling brain. I hope they >>>> don't >>>> come for me....they will put me in a cell with Flying Wing Man aka Dr. >>>> R. >>>> S., the guy who slumps glass and gets away with it (sometimes). >>>> >>>> Agent DLZ-130 >>>> >>>> ----- Original Message ----- >>> >>> >>> >>> >> >> >> -------------------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 8.5.339 / Virus Database: 270.12.53/2156 - Release Date: >> 06/05/09 >> 06:24:00 >> >> > > > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.53/2156 - Release Date: 06/05/09 06:24:00 From stainless_steel at suddenlink.net Sun Jun 7 01:22:19 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Sat, 6 Jun 2009 11:22:19 -0500 Subject: [ATM] ATM: Very Large Amatuer Telescope Message-ID: <27A0E2F53A814821A914F38D07719854@R101> Last night I lay awake and dreamed of exactly how I would construct a very large mounting, specifically for a 40" optic. I would build a mounting that has the very best Cassegrain location foci: a "Polar Disc" mounting, like the Isaac Newton telescope the British invented. It is halfway between a "horseshoe" mounting and a fork and a two pier Polar Horse Shoe mounting (ala Hale five meter). Its primary advantage would be that it could have the Cassegrain focus relocated fairly conveniently, depending on where the telescope was aimed. I propose a 40" primary, because I know there are some persons out there who can do one. Somehow, we need some big glass that is accessible to anyone who is not conveniently located, and also, who does NOT have a big deal" plan for some research project for the instrument. And a scheduling system for same, time wise. Of course, it needs to be "sopmewhat" near to Enid, Oklahoma. In other words, I propose to put amatuer astronomy on the "Greek" footing: "Democracy"- everyone gets a chance at using the big scope. I can design the mouint and drive AND GUARANTEE THAT THEY WILL WORK. I designed and built the largest equatorial mounting in Oklahoma; I have the credentials, therefore. Try me. D-LZ130 P.S.- Thanks to all of you who bought my little book this month; I simply can't believe it. It just astonishes me that so many would buy it, when I have everything in it, except Michael Lindner's little (very elegant) Foucault simulator, and will send it all to you free (the different, added articles, in addition to the main thesis. Thank you all.) (Would have to send the extra articles via html email, or as attachments; Michael's wonderful little Foucault simulator, however, is only available in the book). From wa4guu at verizon.net Sun Jun 7 02:30:28 2009 From: wa4guu at verizon.net (Jerry) Date: Sat, 06 Jun 2009 13:30:28 -0400 Subject: [ATM] Ronchi images and figuring help In-Reply-To: <730685.70810.qm@web81908.mail.mud.yahoo.com> Message-ID: <537DB128B0DD41A6BE15CAE3113586F1@D85SJB21> There is some astigmatism showing and some roughness remains. A picture of the pitch lap can help sometimes for me and others to see if it may be trimmed in a manner that will improve results. The astigmatism is seen by the S shaped nature of the bands, particularly the central band. The roughness is seen in the alternating change of the width of the bands. With Ronchi testing alone it is difficult to see if it caused by zones or ripple. If the astigmatism is not induced by stress on the test stand, you will probably work to get the astigmatism out and change the entire mirror from this present condition. Test the mirror on several diameters and see if the astigmatism rotates with the mirror and shows the same when the mirror is positioned the same. If you decide the astigmatism is from flexure on the test stand: The outer 25% or so is overcorrected compared to the simulation. If this is the 9" f:6 mirror you had mentioned in the past it might not be overcorrected so much that it would make the mirror un-acceptable. But it probably is a bit too much. You can view the defect as being a high intermediate zone. If you can push that down you will have a better fit with the simulated Ronchi. There are others here who know more about machine figuring than me. Not having seen what you had before this, I would not want to say how you might fix it. You say it has gotten better so I would say continue with what you have done and see if it gets even better. Jerry -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of TONY BLAKESLEY Sent: Saturday, June 06, 2009 10:35 AM To: atm at atmlist.net Subject: [ATM] Ronchi images and figuring help Hello, I am deciding whether to parabolize my mirror now or try and make a perfect sphere with a perfect edge first. I have been combating TDE for a few weeks now. The ronchi image of the TDE before was pretty bad, the edges hooked severly. I also had a bad central hole. After completing my modified Mirror-o-Matic grinding and polishing machine, I polished for a few hours trying various methods to knock down the TDE. I know have a very smooth even figure with which appears to be a rolled edge. It matches closely to the computer generated ronchi images. I would like to call upon the ATM gurus knowledge and expertise to lead me to whether I should continue spherizing and try to get that perfect edge, or to go ahead and continue on to parabolization. View my ronchi images here: http://blaktony86.fortunecity.com/ronchitesting.html Thanks for the help guys, -Tony _______________________________________________ ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Sun Jun 7 03:17:33 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sat, 6 Jun 2009 11:17:33 -0700 Subject: [ATM] Ronchi images and figuring help In-Reply-To: <730685.70810.qm@web81908.mail.mud.yahoo.com> References: <730685.70810.qm@web81908.mail.mud.yahoo.com> Message-ID: <002201c9e6d3$15911f50$40b35df0$@com> >>> I am deciding whether to parabolize my mirror now or try and make a perfect sphere with a perfect edge first. I have been combating TDE for a few weeks now. The ronchi image of the TDE before was pretty bad, the edges hooked severly. I also had a bad central hole. After completing my modified Mirror-o-Matic grinding and polishing machine, I polished for a few hours trying various methods to knock down the TDE. I know have a very smooth even figure with which appears to be a rolled edge. It matches closely to the computer generated ronchi images. I would like to call upon the ATM gurus knowledge and expertise to lead me to whether I should continue spherizing and try to get that perfect edge, or to go ahead and continue on to parabolization. View my ronchi images here: http://blaktony86.fortunecity.com/ronchitesting.html <<< Well, what you have is a very common figure. It can be interpreted in more than one way. 1) rolled edge starting at 80% zone outward 2) low 80% zone 3) low edge with high center A key question: as you've been reducing the turned edge, has the point that it begins to roll moved closer to the edge? If so, then continue with either short strokes or long strokes to "push" the roll point off the edge. Another key question: do the ends of the strokes happen to place the 80% zone of the mirror over the lap's edge? If so, do any stroke length but that length. With any small set of images it is impossible to be definitive and difficult to say something meaningful, but I would be hesitant to call this surface "smooth". Which leads to another key question: is the machine set to polish too fast? Or, is the mirror and tool not exactly at room temperature before beginning a spell? I suggest you demonstrate to yourself control over the figure by straightening the bands. Parabolizing from a wobbly figure is putting yourself in a tough position where you have to be a magician to pull it off. Mel Bartels From vorblesnak at peak.org Sun Jun 7 05:08:19 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Sat, 6 Jun 2009 13:08:19 -0700 (PDT) Subject: [ATM] Fused glass and foam update, ronchi pic Message-ID: <4055.69.59.200.230.1244318899.squirrel@webmail.peak.org> Here is a rather pour ronchi picture of the 16 inch fused glass and foam blank. This is at about three hours of polishing. I will probably have a 12 inch mirror when I cut away the warped outer edge. 60 inch focal length. http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/FoamProgress/3%20hrs%20polish.JPG The shot is about 0.25" inside ROC. 50 line grid. David Davis Toledo, OR 97391 From blaktony86 at yahoo.com Sun Jun 7 05:10:18 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Sat, 6 Jun 2009 13:10:18 -0700 (PDT) Subject: [ATM] Ronchi images and figuring help Message-ID: <668533.54835.qm@web81908.mail.mud.yahoo.com> Thanks for the info. The TDE has been reduced by not becoming "hooked" as bad near the edge. Instead it has slowly "rolled" toward the center of the mirror. I do believe my strokes happen to place the lap edge at the 80% zone. I will probably change my stroke. Good idea, I probably should tackle making a perfect sphere before continuing to parabolize. The tool and mirror are at the same temp before polishing so that isnt an issue. Lap looks good. The surface is smooth. These pictures defintley do no justice because they are taken from my crappy camera phone. I will do as you suggest and continue to spherize and fix the edge. -Tony --- On Sat, 6/6/09, Mel Bartels wrote: From: Mel Bartels Subject: Re: [ATM] Ronchi images and figuring help To: atm at atmlist.net Date: Saturday, June 6, 2009, 1:17 PM >>> I am deciding whether to parabolize my mirror now or try and make a perfect sphere with a perfect edge first. I have been combating TDE for a few weeks now. The ronchi image of the TDE before was pretty bad, the edges hooked severly. I also had a bad central hole. After completing my modified Mirror-o-Matic grinding and polishing machine, I polished for a few hours trying various methods to knock down the TDE. I know have a very smooth even figure with which appears to be a rolled edge. It matches closely to the computer generated ronchi images. I would like to call upon the ATM gurus knowledge and expertise to lead me to whether I should continue spherizing and try to get that perfect edge, or to go ahead and continue on to parabolization. View my ronchi images here: http://blaktony86.fortunecity.com/ronchitesting.html <<< Well, what you have is a very common figure.? It can be interpreted in more than one way. 1) rolled edge starting at 80% zone outward 2) low 80% zone 3) low edge with high center A key question: as you've been reducing the turned edge, has the point that it begins to roll moved closer to the edge?? If so, then continue with either short strokes or long strokes to "push" the roll point off the edge. Another key question: do the ends of the strokes happen to place the 80% zone of the mirror over the lap's edge?? If so, do any stroke length but that length. With any small set of images it is impossible to be definitive and difficult to say something meaningful, but I would be hesitant to call this surface "smooth".? Which leads to another key question: is the machine set to polish too fast?? Or, is the mirror and tool not exactly at room temperature before beginning a spell? I suggest you demonstrate to yourself control over the figure by straightening the bands. Parabolizing from a wobbly figure is putting yourself in a tough position where you have to be a magician to pull it off. Mel Bartels _______________________________________________ ATM mailing list http://www.atmlist.net/ From vorblesnak at peak.org Sun Jun 7 05:10:34 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Sat, 6 Jun 2009 13:10:34 -0700 (PDT) Subject: [ATM] Tessellated Blank update Message-ID: <4065.69.59.200.230.1244319034.squirrel@webmail.peak.org> Here is a picture of the blank after 70 wets of 120 grit. Still not in full contact, but getting close. Probably another 20 wets. http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/70%20wets.JPG David Davis Toledo, OR 97391 From blaktony86 at yahoo.com Sun Jun 7 05:13:29 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Sat, 6 Jun 2009 13:13:29 -0700 (PDT) Subject: [ATM] Ronchi images and figuring help Message-ID: <677705.89346.qm@web81901.mail.mud.yahoo.com> Thanks for the input. I am 100% certain it is not astigmatism. I have had a mirror with astigmatism in the past and I learned a great deal from fixing it. This mirror is constantly rotate and is spun on a turntable on the grinding machine. It is also a full thickness pyrex mirror so the test stand isnt introducing any astigmatism into the ronchi image. Again im sorry for the poor quality image. It is way out of focus and I had to rotate/stretch/skew the image to format it onto the web to a decent size. I will continue to deal with the edge problems as you and Mel Bartels mentions. Thanks, Tony --- On Sat, 6/6/09, Jerry wrote: From: Jerry Subject: RE: [ATM] Ronchi images and figuring help To: "'TONY BLAKESLEY'" , atm at atmlist.net Date: Saturday, June 6, 2009, 12:30 PM There is some astigmatism showing and some roughness remains. A picture of the pitch lap can help sometimes for me and others to see if it may be trimmed in a manner that will improve results. The astigmatism is seen by the S shaped nature of the bands, particularly the central band. The roughness is seen in the alternating change of the width of the bands. With Ronchi testing alone it is difficult to see if it caused by zones or ripple. If the astigmatism is not induced by stress on the test stand, you will probably work to get the astigmatism out and change the entire mirror from this present condition. Test the mirror on several diameters and see if the astigmatism rotates with the mirror and shows the same when the mirror is positioned the same. If you decide the astigmatism is from flexure on the test stand: The outer 25% or so is overcorrected compared to the simulation. If this is the 9" f:6 mirror you had mentioned in the past it might not be overcorrected so much that it would make the mirror un-acceptable. But it probably is a bit too much. You can view the defect as being a high intermediate zone. If you can push that down you will have a better fit with the simulated Ronchi. There are others here who know more about machine figuring than me. Not having seen what you had before this, I would not want to say how you might fix it. You say it has gotten better so I would say continue with what you have done and see if it gets even better. Jerry -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of TONY BLAKESLEY Sent: Saturday, June 06, 2009 10:35 AM To: atm at atmlist.net Subject: [ATM] Ronchi images and figuring help Hello, I am deciding whether to parabolize my mirror now or try and make a perfect sphere with a perfect edge first. I have been combating TDE for a few weeks now. The ronchi image of the TDE before was pretty bad, the edges hooked severly. I also had a bad central hole. After completing my modified Mirror-o-Matic grinding and polishing machine, I polished for a few hours trying various methods to knock down the TDE. I know have a very smooth even figure with which appears to be a rolled edge. It matches closely to the computer generated ronchi images. I would like to call upon the ATM gurus knowledge and expertise to lead me to whether I should continue spherizing and try to get that perfect edge, or to go ahead and continue on to parabolization. View my ronchi images here: http://blaktony86.fortunecity.com/ronchitesting.html Thanks for the help guys, -Tony _______________________________________________ ATM mailing list http://www.atmlist.net/ From blaktony86 at yahoo.com Sun Jun 7 05:50:24 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Sat, 6 Jun 2009 13:50:24 -0700 (PDT) Subject: [ATM] Tessellated Blank update Message-ID: <338907.11115.qm@web81905.mail.mud.yahoo.com> This is really neat! I can wait to see what the Ronchi images of this will produce! -Tony --- On Sat, 6/6/09, vorblesnak at peak.org wrote: From: vorblesnak at peak.org Subject: [ATM] Tessellated Blank update To: atm at atmlist.net Date: Saturday, June 6, 2009, 3:10 PM Here is a picture of the blank after 70 wets of 120 grit. Still not in full contact, but getting close. Probably another 20 wets. http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/70%20wets.JPG David Davis Toledo, OR 97391 _______________________________________________ ATM mailing list http://www.atmlist.net/ From stainless_steel at suddenlink.net Sun Jun 7 07:03:02 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Sat, 6 Jun 2009 17:03:02 -0500 Subject: [ATM] Ronchi images and figuring help In-Reply-To: <537DB128B0DD41A6BE15CAE3113586F1@D85SJB21> References: <537DB128B0DD41A6BE15CAE3113586F1@D85SJB21> Message-ID: <65CE73F1AD454E49BA6B78C398D949D2@R101> Abandon Ronchi- use foucault- http://www.atmsite.org/contrib/Harbour/Foucault.html D-LZ130 ----- Original Message ----- From: "Jerry" To: "'TONY BLAKESLEY'" ; Sent: Saturday, June 06, 2009 12:30 PM Subject: Re: [ATM] Ronchi images and figuring help > There is some astigmatism showing and some roughness remains. > > A picture of the pitch lap can help sometimes for me and others to see if > it > may be trimmed in a manner that will improve results. > > The astigmatism is seen by the S shaped nature of the bands, particularly > the central band. > > The roughness is seen in the alternating change of the width of the bands. > With Ronchi testing alone it is difficult to see if it caused by zones or > ripple. > > If the astigmatism is not induced by stress on the test stand, you will > probably work to get the astigmatism out and change the entire mirror from > this present condition. Test the mirror on several diameters and see if > the > astigmatism rotates with the mirror and shows the same when the mirror is > positioned the same. > > If you decide the astigmatism is from flexure on the test stand: > The outer 25% or so is overcorrected compared to the simulation. If this > is > the 9" f:6 mirror you had mentioned in the past it might not be > overcorrected so much that it would make the mirror un-acceptable. But it > probably is a bit too much. You can view the defect as being a high > intermediate zone. If you can push that down you will have a better fit > with > the simulated Ronchi. There are others here who know more about machine > figuring than me. > > Not having seen what you had before this, I would not want to say how you > might fix it. You say it has gotten better so I would say continue with > what > you have done and see if it gets even better. > > > Jerry > > > > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of > TONY BLAKESLEY > Sent: Saturday, June 06, 2009 10:35 AM > To: atm at atmlist.net > Subject: [ATM] Ronchi images and figuring help > > Hello, > > I am deciding whether to parabolize my mirror now or try and make a > perfect > sphere with a perfect edge first. I have been combating TDE for a few > weeks > now. The ronchi image of the TDE before was pretty bad, the edges hooked > severly. I also had a bad central hole. After completing my modified > Mirror-o-Matic grinding and polishing machine, I polished for a few hours > trying various methods to knock down the TDE. I know have a very smooth > even > figure with which appears to be a rolled edge. It matches closely to the > computer generated ronchi images. I would like to call upon the ATM gurus > knowledge and expertise to lead me to whether I should continue spherizing > and try to get that perfect edge, or to go ahead and continue on to > parabolization. View my ronchi images here: > > http://blaktony86.fortunecity.com/ronchitesting.html > > Thanks for the help guys, > > -Tony > _______________________________________________ > 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: 8.5.339 / Virus Database: 270.12.54/2158 - Release Date: 06/06/09 05:53:00 From rmay at nethere.com Sun Jun 7 07:07:51 2009 From: rmay at nethere.com (Bob May) Date: Sat, 6 Jun 2009 15:07:51 -0700 Subject: [ATM] Ronchi images and figuring help References: <730685.70810.qm@web81908.mail.mud.yahoo.com> Message-ID: <001e01c9e6f3$3cf99200$12fe1345@amd> Do a Foucault to see how bad the edge is for the roll and if it is well within the parabola, you are doing good. You do have a minor hook at the edge but working the parabola by working the outside down may get rid of it the way it is now. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Sun Jun 7 07:21:44 2009 From: rmay at nethere.com (Bob May) Date: Sat, 6 Jun 2009 15:21:44 -0700 Subject: [ATM] Tessellated Blank update References: <4065.69.59.200.230.1244319034.squirrel@webmail.peak.org> Message-ID: <002601c9e6f5$2d48ede0$12fe1345@amd> Yep, it took a large number of wets on my 8" to get a full coverage of the grinding. Helps when the mold is accurately ground first for the mirror surface. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From blaktony86 at yahoo.com Sun Jun 7 09:24:00 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Sat, 6 Jun 2009 17:24:00 -0700 (PDT) Subject: [ATM] UPDATE: ronchi images and figuring Message-ID: <128150.54527.qm@web81907.mail.mud.yahoo.com> Hello, OK, I am getting kind of confused by my new ronchi images. I did an hour on the grinding machine with a full size lap, tool on top with standard 1/3 COC strokes. Turntable is about 11rpm and eccentric is 17rpm. A good speed for polishing IMO (not too fast). Before it appeared I had a rolled edge but now it appears (atleast under ronchi test) that I am at a near parabola. This polishing spell seems to have smoothed out my rolled edge and now when I compare it to the computer generated image it looks nearly identical. Should I go ahead and Foucault test or what? I wasnt intentionally trying for a parabola, rather trying for a sphere. Now my lines almost seem to match the lines as the computer generated parabola. Please let me know what you guys think. http://blaktony86.fortunecity.com/ronchitesting.html Thanks again, -Tony From mbartels at bbastrodesigns.com Sun Jun 7 10:23:00 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sat, 6 Jun 2009 18:23:00 -0700 Subject: [ATM] UPDATE: ronchi images and figuring In-Reply-To: <128150.54527.qm@web81907.mail.mud.yahoo.com> References: <128150.54527.qm@web81907.mail.mud.yahoo.com> Message-ID: <002c01c9e70e$853ebed0$8fbc3c70$@com> >>> OK, I am getting kind of confused by my new ronchi images. I did an hour on the grinding machine with a full size lap, tool on top with standard 1/3 COC strokes. Turntable is about 11rpm and eccentric is 17rpm. A good speed for polishing IMO (not too fast). Before it appeared I had a rolled edge but now it appears (atleast under ronchi test) that I am at a near parabola. This polishing spell seems to have smoothed out my rolled edge and now when I compare it to the computer generated image it looks nearly identical. Should I go ahead and Foucault test or what? I wasnt intentionally trying for a parabola, rather trying for a sphere. Now my lines almost seem to match the lines as the computer generated parabola. Please let me know what you guys think. http://blaktony86.fortunecity.com/ronchitesting.html <<< Careful here, not to be so optimistic that you selectively ignore contrary evidence. The snap in the Ronchi band closest to the edge in the outside of radius of curvature is still quite pronounced. What I see is that you polished some more, and that the 80% zone that had been dug before is ever so slightly less pronounced, because the polishing has simply lowered the level of the glass surface on average. You might try a star test and see if you're satisfied. If not, then continue with what you just did. Mel Bartels From foreilly at bestweb.net Mon Jun 8 01:26:42 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Sun, 7 Jun 2009 12:26:42 -0400 Subject: [ATM] ATM: Very Large Amatuer Telescope References: <27A0E2F53A814821A914F38D07719854@R101> Message-ID: I like your attitude David! Francis From rmay at nethere.com Mon Jun 8 06:49:53 2009 From: rmay at nethere.com (Bob May) Date: Sun, 7 Jun 2009 14:49:53 -0700 Subject: [ATM] Ronchi images and figuring help References: <537DB128B0DD41A6BE15CAE3113586F1@D85SJB21> <65CE73F1AD454E49BA6B78C398D949D2@R101> Message-ID: <001a01c9e7b9$e46a2f60$dafe1345@amd> Bah, humbug! Ya can't trust any of them! Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Mon Jun 8 06:54:08 2009 From: rmay at nethere.com (Bob May) Date: Sun, 7 Jun 2009 14:54:08 -0700 Subject: [ATM] UPDATE: ronchi images and figuring References: <128150.54527.qm@web81907.mail.mud.yahoo.com> Message-ID: <002301c9e7ba$7c58d6a0$dafe1345@amd> Tony, the Foucautl test isn't that hard. Just go and do it and run the numbers through TEX or FringeXP. You will then be able to see exactly what the surface is really like. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From vladimir.galogaza1 at zg.t-com.hr Mon Jun 8 18:00:29 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Mon, 8 Jun 2009 11:00:29 +0200 Subject: [ATM] UPDATE: ronchi images and figuring References: <128150.54527.qm@web81907.mail.mud.yahoo.com> <002301c9e7ba$7c58d6a0$dafe1345@amd> Message-ID: <2DAE0C9FD53B49758B0B0FA246A8A558@piv555a133b59e> >Tony, the Foucautl test isn't that hard. Just go and do it and >run the numbers through TEX or FringeXP. You will then be able >to see exactly what the surface is really like. This was sound advice of a realy experienced ATM. And yet in my (NSH) opinion, for novice starting the Foucault testing from scratch and without experience is not a bit easier that start with interferometric testing via Bath interferometer. Advantage is that only this will show "what the surface is realy like". Foucault will tell about status of one of its diameters. For other diameters more testing is called for. Interferometry will provide results in one go, much faster and with less data entry procedures. Effort to build good Foucault test rig is about the same as for building good Bath interferometer. Subjective judgments, like ones about shadows and distance readings, required in Foucault test, are absent in interferometry procedure. What is today easily available in interferometry (equipment and programs) justifies my expectation that it should be preferred test method for ATMs. Regards Vladimir. PS If to somebody this looks like plain interferometry propaganda, this is ok because it is meant to be just this. From rflrs at verizon.net Mon Jun 8 18:45:19 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Mon, 08 Jun 2009 05:45:19 -0400 Subject: [ATM] Triplet In-Reply-To: <4A19EB73.40300@verizon.net> References: <3183d250711090321l23b17e67y71bc7189909483f8@mail.gmail.com> <920703.73390.qm@web82005.mail.mud.yahoo.com> <4A19EB73.40300@verizon.net> Message-ID: <4A2CDDAF.6010308@verizon.net> Richard F.L.R. Snashall wrote: > > The disadvantage here is that the spherochromatism > is 2.7 to 3 times higher. 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 The last surface is no longer as flat, with a sagitta of nearly 150 microns. However, the default amount of figuring is smaller -- less than 1/8 micron from the best fit sphere. From foreilly at verizon.net Mon Jun 8 20:59:50 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Mon, 08 Jun 2009 07:59:50 -0400 Subject: [ATM] Look Ma! No channels! Message-ID: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95> I just finished a half hour hand polishing surface on a newly fine ground flat. I had rechanneled the tool before polishing. By the time I was fifteen minutes into the session, the channels had all but closed up. Polishing was laborious at best requiring all of my strength to move the flat over the lap. At fifteen minutes, I switched to the lap on top. I got quite the workout! Evidently so did my flat. I have achieved a really good faux polish, better then I have ever seen before at that stage. The fine grinding was done with three micron Aluminum Oxide, the polishing compound was #85 liquid polishing compound from Universal Photonics on the Island (Long Isalnd). Just a post, no particular reason to share this otherwise. Best, Francis J. O'Reilly From mjc5 at psu.edu Mon Jun 8 22:02:12 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 08 Jun 2009 09:02:12 -0400 Subject: [ATM] Look Ma! No channels! In-Reply-To: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95> References: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95> Message-ID: <4819487D-2BCB-464B-99B7-4D21F12D1A86@psu.edu> On Jun 8, 2009, at 7:59 AM, Francis J. O'Reilly wrote: > I just finished a half hour hand polishing surface on a newly fine > ground flat. I had rechanneled the tool before polishing. By the > time I was fifteen minutes into the session, the channels had all > but closed up. Polishing was laborious at best requiring all of my > strength to move the flat over the lap. > > At fifteen minutes, I switched to the lap on top. I got quite the > workout! > > Evidently so did my flat. I have achieved a really good faux polish, > better then I have ever seen before at that stage. Faux? -73 de Mike N3LI - From foreilly at bestweb.net Mon Jun 8 22:06:31 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Mon, 8 Jun 2009 09:06:31 -0400 Subject: [ATM] Look Ma! No channels! References: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95> <4819487D-2BCB-464B-99B7-4D21F12D1A86@psu.edu> Message-ID: It looks good from afar, but it is really a fake polish, pits abound and will do so for another couple of hours of work. Sort of like when a woman buys what she thinks is a mink coat and it is really rabbit. ----- Original Message ----- From: "Michael Coslo" To: "List atm" Sent: Monday, June 08, 2009 9:02 AM Subject: Re: [ATM] Look Ma! No channels! > > On Jun 8, 2009, at 7:59 AM, Francis J. O'Reilly wrote: > >> I just finished a half hour hand polishing surface on a newly fine >> ground flat. I had rechanneled the tool before polishing. By the time I >> was fifteen minutes into the session, the channels had all but closed >> up. Polishing was laborious at best requiring all of my strength to move >> the flat over the lap. >> >> At fifteen minutes, I switched to the lap on top. I got quite the >> workout! >> >> Evidently so did my flat. I have achieved a really good faux polish, >> better then I have ever seen before at that stage. > > > Faux? > > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From foreilly at bestweb.net Mon Jun 8 23:38:02 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Mon, 8 Jun 2009 10:38:02 -0400 Subject: [ATM] Look Ma! No channels! References: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95><4819487D-2BCB-464B-99B7-4D21F12D1A86@psu.edu> <4EC3E775D68646F98263405310C7B351@piv555a133b59e> Message-ID: <62B34504104B416F9462D17FF37850B9@D5GHLR11> Vladmir, If the flat was just to calibrate a spherometer, I would agree that pits were not an issue. I don't want pits in my flats as I am going to aluminize at least one of them drill a central hole and use it for autocollimation purposes. Other than that, I just want them to be as neat as possible. Further, I am making a total of three seven inch (175mm) two sided flats. The prime reason for so many flat surfaces is that I want to gain experience making small flats before I move onto something larger. My next project will be a 12.25" (310mm) flat and from there I will go either to a sixteen inch or a twenty-four inch flat. All for autocollimation purposes. The glass for these will be very expensive so these will likely be a long range project. Francis ----- Original Message ----- From: "Vladimir Galogaza" To: "Francis J. O'Reilly" Sent: Monday, June 08, 2009 10:03 AM Subject: Re: [ATM] Look Ma! No channels! > Hi Francis, > >>It looks good from afar, but it is really a fake polish, pits abound and >>will do so for another couple of hours of work. > > What is in your opinion wrong in having pits in polished flat? > Do you find that there is too much of them, by number or size? > What is your judgment about the proportion of the area of pits > to the total area of the flat? > > Regards > Vladimir. From wkitty42 at windstream.net Tue Jun 9 02:21:36 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Mon, 08 Jun 2009 13:21:36 -0400 Subject: [ATM] UPDATE: ronchi images and figuring In-Reply-To: <2DAE0C9FD53B49758B0B0FA246A8A558@piv555a133b59e> References: <128150.54527.qm@web81907.mail.mud.yahoo.com> <002301c9e7ba$7c58d6a0$dafe1345@amd> <2DAE0C9FD53B49758B0B0FA246A8A558@piv555a133b59e> Message-ID: <4A2D48A0.8070000@windstream.net> Vladimir Galogaza wrote: >> Tony, the Foucautl test isn't that hard. Just go and do it and >> run the numbers through TEX or FringeXP. You will then be able >> to see exactly what the surface is really like. > > This was sound advice of a realy experienced ATM. > > And yet in my (NSH) opinion, for novice starting the Foucault testing from > scratch and without experience is not a bit easier that start with > interferometric testing via Bath interferometer. is there, somewhere, a link to plans for an easy to build Bath interferometer like there are for the foucault testers? [trim] > > PS > If to somebody this looks like plain interferometry propaganda, this is ok > because it is meant to be just this. hehehe ;) -- _\/ (@@) 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 Tue Jun 9 04:28:55 2009 From: rmay at nethere.com (Bob May) Date: Mon, 8 Jun 2009 12:28:55 -0700 Subject: [ATM] UPDATE: ronchi images and figuring References: <634362.26493.qm@web54507.mail.re2.yahoo.com> Message-ID: <000601c9e86f$5e227460$04985545@amd> OOPTHH111 Yep, FigureXP is the one. I prefer TEX tho. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From richard1941 at gmail.com Tue Jun 9 09:52:32 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Mon, 8 Jun 2009 18:52:32 -0600 Subject: [ATM] Look Ma! No channels! In-Reply-To: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95> References: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95> Message-ID: If you ground with three micron, there should be no pits. Re-grind with no pressure to get rid of the pits. Still on the road headed east staying just north of Enid OK tonight. Sent from my iPhone On Jun 8, 2009, at 5:59, "Francis J. O'Reilly" wrote: > I just finished a half hour hand polishing surface on a newly fine > ground flat. I had rechanneled the tool before polishing. By the > time I was fifteen minutes into the session, the channels had all > but closed up. Polishing was laborious at best requiring all of my > strength to move the flat over the lap. > > At fifteen minutes, I switched to the lap on top. I got quite the > workout! > > Evidently so did my flat. I have achieved a really good faux polish, > better then I have ever seen before at that stage. > > The fine grinding was done with three micron Aluminum Oxide, the > polishing compound was #85 liquid polishing compound from Universal > Photonics on the Island (Long Isalnd). > > Just a post, no particular reason to share this otherwise. > > Best, > > Francis J. O'Reilly > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From foreilly at bestweb.net Tue Jun 9 11:03:46 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Mon, 8 Jun 2009 22:03:46 -0400 Subject: [ATM] Look Ma! No channels! References: <3518A809D30147DDA92A137A341A0DF2@HELENYLCMWAV95> Message-ID: Richard, We prefer you alive, drive when you're driving and email when you stop! Say hello to David for me. Francis ----- Original Message ----- From: "Richard Schwartz" To: "Francis J. O'Reilly" Cc: ; ; Sent: Monday, June 08, 2009 8:52 PM Subject: Re: [ATM] Look Ma! No channels! > If you ground with three micron, there should be no pits. Re-grind with > no pressure to get rid of the pits. > > Still on the road headed east staying just north of Enid OK tonight. > > Sent from my iPhone > > On Jun 8, 2009, at 5:59, "Francis J. O'Reilly" > wrote: > >> I just finished a half hour hand polishing surface on a newly fine >> ground flat. I had rechanneled the tool before polishing. By the time I >> was fifteen minutes into the session, the channels had all but closed >> up. Polishing was laborious at best requiring all of my strength to move >> the flat over the lap. >> >> At fifteen minutes, I switched to the lap on top. I got quite the >> workout! >> >> Evidently so did my flat. I have achieved a really good faux polish, >> better then I have ever seen before at that stage. >> >> The fine grinding was done with three micron Aluminum Oxide, the >> polishing compound was #85 liquid polishing compound from Universal >> Photonics on the Island (Long Isalnd). >> >> Just a post, no particular reason to share this otherwise. >> >> Best, >> >> Francis J. O'Reilly >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ From blaktony86 at yahoo.com Tue Jun 9 13:06:24 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Mon, 8 Jun 2009 21:06:24 -0700 (PDT) Subject: [ATM] Star Test results - need help Message-ID: <666736.77653.qm@web81903.mail.mud.yahoo.com> Hello, First off let me say I am no expert at star testing. More like a novice. I found some odd results that im not sure of and I need some help. I collimated my scope with my eye (no collimation tool) and pointed it toward the brightest star in the sky. Found the star looked pretty good from past experience. When the star was in the middle of the eyepiece it was perfectly round when I go in and out of focus. Turbulence in the atmosphere was too bad for me to do any "real" testing but I just wanted to see how the optics was performing. As the star drifted toward the edge of the eyepiece, the star became skewed slightly. When I turned the focus in and out of focus, it appeared as if the optics had astigmatism. I have had astigmatism in my first mirror before (6") and this didnt seem like the same thing. I checked multiple points around the eyepiece edge (N, E, S and W) and it all appeared the same. When the star was in the center of the eyepiece it was perfect again. I wanted to make sure there wasnt any astigmatism in the mirror, so I rotated the mirror 1/3 turn. Then I placed the star at the edge of the eyepiece and it behaved exactly the same way. Sort of like astigmatism (oval shapes flipping direction when taken in and out of focus). I am just confused why this only happens at the edge of the eyepiece. Do I have some kind of off axis optical alignment? Are there other causes of this? I dont believe its in the mirror, the ronchi lines remained the same angle, in and out of the COC. Plus the mirror was ground and polished on a grinding machine so chances of astigmatism are greatly reduced. My optical system are as follows: 9.2" F/5.87 1.83" M.A. secondary The only thing I can think of is if the secondary isnt perfectly centered in the tube. But wouldnt collimation take care of this? Are there any kind of figuring errors that can behave as what I described? Thanks, -Tony From mbartels at bbastrodesigns.com Tue Jun 9 13:20:24 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Mon, 8 Jun 2009 21:20:24 -0700 Subject: [ATM] Star Test results - need help In-Reply-To: <666736.77653.qm@web81903.mail.mud.yahoo.com> References: <666736.77653.qm@web81903.mail.mud.yahoo.com> Message-ID: <003801c9e8b9$a1c18d60$e544a820$@com> >>> Turbulence in the atmosphere was too bad for me to do any "real" testing but I just wanted to see how the optics was performing. <<< Star testing during bad seeing is not only problematic, but can be misleading! >>> As the star drifted toward the edge of the eyepiece, the star became skewed slightly. When I turned the focus in and out of focus, it appeared as if the optics had astigmatism. <<< Only test in the middle of the field of view. Most eyepieces produce astigmatic images as you let the star drift towards the edge. That's why I like to use Polaris as my test star. Also, use medium then high power. Low power tests the eye more than the optics. Mel Bartels From vorblesnak at peak.org Tue Jun 9 13:28:20 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Mon, 8 Jun 2009 21:28:20 -0700 (PDT) Subject: [ATM] Work report on the glass and foam blanks Message-ID: <35818.208.51.52.146.1244521700.squirrel@webmail.peak.org> June 8th report on the glass and foam blanks .. I remember now that I do not like to make telescope mirrors. It is tedious and makes my back hurt and I think I do it just to suffer. The pitch is too hard I think. The polishing on the fused blank is very slow. I cold pressed all night with about 40 pounds of weight on the tool, (tool on top with a plastic bird screen between it and the glass), and it barely dented the pitch. I was going to strip it and melt one last time and I found a can of Gugolz?? in my barrel of stuff. So I am going to add a layer. Still have a hole in the middle and rough surface. About 7 hours of work. The tessellated blank .. I ran out of 120 grit and shifted to 220 thinking I was close enough to grind the last of the problems out. Tomorrow I will buy more 120. It's just easier. But! It did smooth the surface enough that I was able to do a basic focal length test with the setting sun. I got a fuzzy spot about the size of a 50 cent piece and a tighter spot about the size of a nickle. Pretty close to a 56 inch focal length which makes it a tad over f3. Close enough for a prototype. David Davis Toledo, OR 97391 From rflrs at verizon.net Tue Jun 9 19:16:23 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Tue, 09 Jun 2009 06:16:23 -0400 Subject: [ATM] Triplet In-Reply-To: <4A2CDDAF.6010308@verizon.net> References: <3183d250711090321l23b17e67y71bc7189909483f8@mail.gmail.com> <920703.73390.qm@web82005.mail.mud.yahoo.com> <4A19EB73.40300@verizon.net> <4A2CDDAF.6010308@verizon.net> Message-ID: <4A2E3677.8070306@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 Yes, but I'm sure you're all asking the question "Can it be done with all spherical surfaces?". By pushing the crown out a bit more (not much room left, though), I found a combination that, in order to correct the zonal error, needed to only be about 8.5 nm from spherical on the last surface. Forcing the design all-spherical, and optimizing only with respect to focal length and visual RMS wavefront error (again, 135 mm f/12): http://mysite.verizon.net/rflrs/trp02-32x.atm ATMOS input file http://mysite.verizon.net/rflrs/trp02-32x.len OSLO input file http://mysite.verizon.net/rflrs/trp02-32x.txt TEXT prescription http://mysite.verizon.net/rflrs/trp02-32x.zmx ZEMAX input file I realize that N-SK14 is not your most resistant glass, but at least it's better than N-SK16, and it's interior to the tube. With the wavelengths given in the input files, it appears that color at the 70% zone is slightly undercorrected, about 1 part in 16000, or so, for the C-F range. However, that appearance is deceptive. Looking at a wider band, light at wavelengths of about 382 nm and 1360 nm also cross the green e line at the 70% zone. From mjc5 at psu.edu Tue Jun 9 21:41:07 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Tue, 09 Jun 2009 08:41:07 -0400 Subject: [ATM] Star Test results - need help In-Reply-To: <666736.77653.qm@web81903.mail.mud.yahoo.com> References: <666736.77653.qm@web81903.mail.mud.yahoo.com> Message-ID: On Jun 9, 2009, at 12:06 AM, TONY BLAKESLEY wrote: > Hello, > > First off let me say I am no expert at star testing. More like a > novice. I found some odd results that im not sure of and I need some > help. > > I collimated my scope with my eye (no collimation tool) and pointed > it toward the brightest star in the sky. Found the star looked > pretty good from past experience. When the star was in the middle of > the eyepiece it was perfectly round when I go in and out of focus. > Turbulence in the atmosphere was too bad for me to do any "real" > testing but I just wanted to see how the optics was performing. > > As the star drifted toward the edge of the eyepiece, the star became > skewed slightly. When I turned the focus in and out of focus, it > appeared as if the optics had astigmatism. I have had astigmatism in > my first mirror before (6") and this didnt seem like the same thing. > I checked multiple points around the eyepiece edge (N, E, S and W) > and it all appeared the same. When the star was in the center of the > eyepiece it was perfect again. Hiya Tony, As I learned, Star testing is best done over a long period of time. I tested mine for several months. Seeing varies, and can skew the results. I would guess from your description, you might not be in too bad shape. But one test, esp under poor conditions, does not a good mirror reveal. The other thing is that your off centered images are more an indication of your eyepiece, not your mirror system. Off axis performance suffers in most ep's. Always star test in the center of the fov. -73 de Mike N3LI - From al at sgi.com Tue Jun 9 21:54:08 2009 From: al at sgi.com (Alexis Cousein) Date: Tue, 09 Jun 2009 14:54:08 +0200 Subject: [ATM] Star Test results - need help In-Reply-To: References: <666736.77653.qm@web81903.mail.mud.yahoo.com> Message-ID: <4A2E5B70.8080202@sgi.com> Michael Coslo wrote: > > The other thing is that your off centered images are more an indication > of your eyepiece, not your mirror system. Off axis performance suffers > in most ep's. Always star test in the center of the fov. > > -73 de Mike N3LI - > Also, depending on the exit pupil and the eyepiece AFOV, the edge might also be affected by the mirror's coma (or a combination of eyepiece astigmatism and mirror coma). In a slowish scope it doesn't degrade the in-focus start image a lot, but it's usually all blatantly obvious when you star test with a star a the edge (even the diffraction limited field of a Newt is limited, and the star test is sensitive enough to detect differences much smaller than that). From mjc5 at psu.edu Tue Jun 9 21:54:42 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Tue, 09 Jun 2009 08:54:42 -0400 Subject: [ATM] Work report on the glass and foam blanks In-Reply-To: <35818.208.51.52.146.1244521700.squirrel@webmail.peak.org> References: <35818.208.51.52.146.1244521700.squirrel@webmail.peak.org> Message-ID: On Jun 9, 2009, at 12:28 AM, vorblesnak at peak.org wrote: > > I remember now that I do not like to make telescope > mirrors. It is tedious and makes my back hurt and I > think I do it just to suffer. Hang in there Dave. > > > The pitch is too hard I think. The polishing on the > fused blank is very slow. I cold pressed all night > with about 40 pounds of weight on the tool, (tool > on top with a plastic bird screen between it and > the glass), and it barely dented the pitch. I concur. Your lap is way too hard. > I was > going to strip it and melt one last time and I found > a can of Gugolz?? in my barrel of stuff. So I am > going to add a layer. Still have a hole in the > middle and rough surface. About 7 hours of work. I'm not sure how the different hardnesses of pitch will act. I know I would re-melt the present pitch, and add some turpentine and mineral oil. I used around 2 teaspoons of turp and two tablespoons of mineral oil for a 12.5 inch lap. I probably overdid the mineral oil - I got pretty soft pitch as a result. But it polished that glass beautifully. Some have said that too soft pitch can give a turned down edge, but I've also hear the opposite, so everything gives a TDE - ha! Interesting enough, I used the softer pitch lap to correct TDE. -73 de Mike N3LI - From hrd9 at juno.com Wed Jun 10 04:35:28 2009 From: hrd9 at juno.com (horace r davis) Date: Tue, 9 Jun 2009 15:35:28 -0400 Subject: [ATM] the Pyrex mirror casting worked Message-ID: <20090609.153528.5696.0.hrd9@juno.com> The 15" Pyrex blank I shipped to Tom stokes was stress free. A new problem has came up the kiln wash which I use to coat the casting came off in places and flaked into the glass. On my next blank a 20" x 1.6" I will try to use very little kiln wash hope that the mold holds if not I will lose the kiln. This is just part of the fun of trying some thing new. My long range goal is to cast a blank some thing like the one Thomas Janstrom did only for a 18 point mirror cell. That will be the next 20" after this one. If some one would like to help me with a good rib design for a light weight 20" that matches a mirror cell I will cut you a break on the cost of the blank. We should be able to get 20" scope it the 80 to 100 lb range. ____________________________________________________________ Let your voice be heard! Click here and get paid to participate in surveys! http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTEFxLmYt1zxP0L1FY24eW747yFcyJugjpz0bPjrB34YdV7dCgDn92/ From rmay at nethere.com Wed Jun 10 05:03:28 2009 From: rmay at nethere.com (Bob May) Date: Tue, 9 Jun 2009 13:03:28 -0700 Subject: [ATM] Work report on the glass and foam blanks References: <35818.208.51.52.146.1244521700.squirrel@webmail.peak.org> Message-ID: <001101c9e93d$5c3f50e0$d1fe1345@amd> >From the experience that I've gotten with your blank, DO NOT PUT ANY WEIGHT ON THE MIRROR or you will get a really strange figure! If you want a polish and don't care about the figure, put some weight on it and push fast. You WILL get a really strange figure tho which will take some time to get worked out. There will be hills and valleys all over the place! They will not be concentric either! Be aware that if you're moving lightly over a lap, you ain't polishing! The higher the force to move the glass over the lap, the more work is being done and weight doesn't matter with this requirement. Actually, more weight is the wrong thing to do as it adds in plain friction to the drag of a lap in proper operation and you don't feel the proper drag as well and thus lose what the proper feel is. For the grinding blank, do the ROC flashlight test to see what the shape of the mirror is. Being able to see the shape will let you know better than looking at an image at the focal plane. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From jbentz at inreach.com Wed Jun 10 06:13:34 2009 From: jbentz at inreach.com (Jan Bentz) Date: Tue, 09 Jun 2009 14:13:34 -0700 Subject: [ATM] Lithium Flouride Apo Message-ID: <4A2ED07E.7020703@inreach.com> I have a design worked up for a Quartz + LiF Apo doublet that looks to be quite the challenge. One of the problems I can forsee is the durability of LiF. Even though this element will be to the rear of the quartz as in a Steinheil arrangement, does anyone know if the outside (R4) surface will degrade over time? I do know that most of the mechanical properties of this stuff are somewhat less favorable in the optical shop than CaF. But since CaF has been used in doublets is it at all practical to try LiF? Why, you may ask, am I looking for trouble? Three reasons- I've never heard of anyone trying this before; I refuse to pay thousands of dollars for something I might be able to make myself; and most importantly I happened to come into the possesion of a 6" x 1" piece. Jan Bentz From tstokes at pacbell.net Wed Jun 10 08:50:30 2009 From: tstokes at pacbell.net (Tom Stokes) Date: Tue, 9 Jun 2009 16:50:30 -0700 Subject: [ATM] Horace Davis Message-ID: <130F5762A33842D1A068021C5AE55278@tom> I'm sure most of you have seen Horace's posts on his attempts at casting mirror blanks. He has been trying it for about a year and a half now. I offered to grind and strain test some of his blanks, and about mid June, I received a 15" x 1.5" Pyrex blank. This is a story of my dealings with that blank. http://www.mirrorgrindingmachine.com/horacedavis/ I'm sure it will make a very good mirror for someone. Maybe me! Tom Stokes From atmer at flash.net Wed Jun 10 09:03:07 2009 From: atmer at flash.net (Anthony Stillman) Date: Tue, 9 Jun 2009 17:03:07 -0700 (PDT) Subject: [ATM] Lithium Flouride Apo Message-ID: <981366.35758.qm@web82008.mail.mud.yahoo.com> Jan, Lithium floride is reasonably resistant to chemical attack. It's every so slightly soluble in water. The worst property with which to contend is it's as soft as butter. Get the finished lens coated and keep the scope dry and I don't think you'll have a problem. Good luck with the quartz. Plan on going through lots of grit. Anthony From tstokes at pacbell.net Wed Jun 10 09:15:15 2009 From: tstokes at pacbell.net (Tom Stokes) Date: Tue, 9 Jun 2009 17:15:15 -0700 Subject: [ATM] Horace Davis References: <130F5762A33842D1A068021C5AE55278@tom> Message-ID: <5405D02B32B64B63B648E476E7AC60D9@tom> Correction - received mid May. ----- Original Message ----- From: "Tom Stokes" To: ; Sent: Tuesday, June 09, 2009 4:50 PM Subject: [ATM] Horace Davis > I'm sure most of you have seen Horace's posts on his attempts at casting > mirror blanks. He has been trying it for about a year and a half now. I > offered to grind and strain test some of his blanks, and about mid June, I > received a 15" x 1.5" Pyrex blank. This is a story of my dealings with > that > blank. > > http://www.mirrorgrindingmachine.com/horacedavis/ > > I'm sure it will make a very good mirror for someone. Maybe me! > > Tom Stokes > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From richard1941 at gmail.com Wed Jun 10 09:30:06 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Tue, 9 Jun 2009 19:30:06 -0500 Subject: [ATM] Work report on the glass and foam blanks In-Reply-To: <001101c9e93d$5c3f50e0$d1fe1345@amd> References: <35818.208.51.52.146.1244521700.squirrel@webmail.peak.org> <001101c9e93d$5c3f50e0$d1fe1345@amd> Message-ID: <8889AB8C-CDFC-47E0-A46F-258C1A71CB28@gmail.com> But light pressure and fast strokes did a good job on rib print through and should be tried AFTER surface iz polished out per Bob Mayz advice. Sent from my iPhone On Jun 9, 2009, at 15:03, "Bob May" wrote: >> From the experience that I've gotten with your blank, DO NOT PUT > ANY WEIGHT ON THE MIRROR or you will get a really strange figure! > If you want a polish and don't care about the figure, put some > weight on it and push fast. You WILL get a really strange figure > tho which will take some time to get worked out. There will be > hills and valleys all over the place! They will not be > concentric either! > Be aware that if you're moving lightly over a lap, you ain't > polishing! The higher the force to move the glass over the lap, > the more work is being done and weight doesn't matter with this > requirement. Actually, more weight is the wrong thing to do as > it adds in plain friction to the drag of a lap in proper > operation and you don't feel the proper drag as well and thus > lose what the proper feel is. > For the grinding blank, do the ROC flashlight test to see what > the shape of the mirror is. Being able to see the shape will let > you know better than looking at an image at the focal plane. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From atmpob at yahoo.com Wed Jun 10 10:45:00 2009 From: atmpob at yahoo.com (Dale Eason) Date: Tue, 9 Jun 2009 18:45:00 -0700 (PDT) Subject: [ATM] UPDATE: ronchi images and figuring Message-ID: <227096.83891.qm@web54504.mail.re2.yahoo.com> Waldo, yes there is a link and I have posted it here several times I think. http://starryridge.com/mediawiki-1.9.1/index.php?title=Main_Page The learning curve is about the same for Foucault but the hardware is a little more involved but still easy to construct. It does require one to have a camera to capture the interferogram images to be analyzed by computer software. The least effort cameras to use are Digital SLR's like the Canon Rebel or a Nikon D50. Web cams can be used if the lens is replaced with a longer focus lens. All of this is detailed in the above link. Dale Eason --- On Mon, 6/8/09, waldo kitty wrote: > > is there, somewhere, a link to plans for an easy to build > Bath interferometer like there are for the foucault > testers? > From jbentz at inreach.com Wed Jun 10 11:35:21 2009 From: jbentz at inreach.com (Jan Bentz) Date: Tue, 09 Jun 2009 19:35:21 -0700 Subject: [ATM] Lithium Flouride Apo In-Reply-To: <981366.35758.qm@web82008.mail.mud.yahoo.com> References: <981366.35758.qm@web82008.mail.mud.yahoo.com> Message-ID: <4A2F1BE9.3050501@inreach.com> Anthony Stillman wrote: >Jan, > >Lithium floride is reasonably resistant to chemical attack. It's every so slightly soluble in water. The worst property with which to contend is it's as soft as butter. Get the finished lens coated and keep the scope dry and I don't think you'll have a problem. Good luck with the quartz. Plan on going through lots of grit. > >Anthony > > >_______________________________________________ >ATM mailing list http://www.atmlist.net/ > > > Thanks Anthony, what you say is encouraging although I'm leary of trying to coat the LiF because it gets soft around 450 deg and I'm not sure what they heat up lenses to when they coat. Good suggestion though. NOTE: In the original post I said it was to be combined with fused quartz but checking my calcs for the partial dispersions I found that I was using old and unreliable values for the indices. A redo showed that quartz will not work very well but possibly something like an FK-5 will. Sorry for anybody trying to work one out with quartz. Jan Bentz From wkitty42 at windstream.net Wed Jun 10 12:12:05 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Tue, 09 Jun 2009 23:12:05 -0400 Subject: [ATM] UPDATE: ronchi images and figuring In-Reply-To: <227096.83891.qm@web54504.mail.re2.yahoo.com> References: <227096.83891.qm@web54504.mail.re2.yahoo.com> Message-ID: <4A2F2485.8000202@windstream.net> Dale Eason wrote: > Waldo, > yes there is a link and I have posted it here several times I think. thanks, dale.. i was mainly asking for others who may or may not know about such... i know i've seen references before but don't always think about trying to search back when the topic (not only this one) comes up... i also want/need to thank vladimir galogaza who wrote me offlist on this topic as well... > http://starryridge.com/mediawiki-1.9.1/index.php?title=Main_Page > > The learning curve is about the same for Foucault but the hardware is a little more involved but still easy to construct. It does require one to have a camera to capture the interferogram images to be analyzed by computer software. The least effort cameras to use are Digital SLR's like the Canon Rebel or a Nikon D50. Web cams can be used if the lens is replaced with a longer focus lens. All of this is detailed in the above link. that's something to consider, as well... very important info, that :) > Dale Eason > > --- On Mon, 6/8/09, waldo kitty wrote: > >> is there, somewhere, a link to plans for an easy to build >> Bath interferometer like there are for the foucault >> testers? -- _\/ (@@) 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 vorblesnak at peak.org Wed Jun 10 13:06:33 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Tue, 9 Jun 2009 21:06:33 -0700 (PDT) Subject: [ATM] Work report on the glass and foam blanks Message-ID: <49780.69.59.210.182.1244606793.squirrel@webmail.peak.org> I wondered about your experience with the figure on that blank you have. I had a similar sort of figure on the 15.5 way back when. It was a wild swirl of hills and valleys that came from too much heat and pressure. Remember that glass was only 3/16ths when I started. I wonder of you had some flexure in the adhesive layer? It will be interesting to see if you can pull it out. I've got a mild astigmatism starting in the fused glass and foam blank. I am not sure where it came from as I am polishing on the machine. I don't see any rocking action. I am polishing with the tool on top using a 12 inch lap. I have not trimmed the odd warped glass off of the outer edge and I wonder if it is rocking the lap as it moves. Could be where the hole in the middle came from. I am thinking it is time to trim that weird glass off and get down to the piece I am going to finish. That may solve a multitude problems. I still have some good lines though. The Tessellated Blank ... I am through the 220 grit and getting ready to go to 320 for a while. I stopped for a while to put a flash polish on the glass to see what I had for figure. I have a polish out to the 75% zone, more or less. I get a good reflection of the flashlight across the pieces. That is a heartening thing. It suggests the pieces are at a very close focal length. I might try for a street light refection with a 25mm eyepiece to see if I can see any detail at all. Just playing a bit before I move on to the next grit. I wore out the surface on the tool I was using. I am thinking of using a pie plate as a ring tool for my final grits. David Davis Toledo, OR 97391 >From the experience that I've gotten with your blank, DO NOT PUT >ANY WEIGHT ON THE MIRROR or you will get a really strange figure! >If you want a polish and don't care about the figure, put some >weight on it and push fast. You WILL get a really strange figure >Bob May >rmay at nethere.com >http: slash /nav.to slash bobmay >http: slash /bobmay dot astronomy.net From atmer at flash.net Wed Jun 10 14:12:13 2009 From: atmer at flash.net (Anthony Stillman) Date: Tue, 9 Jun 2009 22:12:13 -0700 (PDT) Subject: [ATM] Lithium Flouride Apo Message-ID: <63153.92162.qm@web82003.mail.mud.yahoo.com> ...gets soft around 450 deg Jan, Yea, I forgot about the thermal issue. Lithium flouride is also sensitive to thermal shock. To have it coated you'll need to take it to a place that's experienced with the difficult. I suggest . There's another place that Kevin Medlock recommended to me years ago, but the name escapes me. Anthony From rflrs at verizon.net Wed Jun 10 14:59:18 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Wed, 10 Jun 2009 01:59:18 -0400 Subject: [ATM] Lithium Flouride Apo In-Reply-To: <4A2ED07E.7020703@inreach.com> References: <4A2ED07E.7020703@inreach.com> Message-ID: <4A2F4BB6.3010706@verizon.net> Jan Bentz wrote: > I have a design worked up for a Quartz + LiF Apo doublet that looks > to be quite the challenge. One of the problems I can forsee is the > durability of LiF. Even though this element will be to the rear of > the quartz as in a Steinheil arrangement, does anyone know if the > outside (R4) surface will degrade over time? I do know that most of > the mechanical properties of this stuff are somewhat less favorable in > the optical shop than CaF. But since CaF has been used in doublets is > it at all practical to try LiF? Why, you may ask, am I looking for > trouble? Three reasons- I've never heard of anyone trying this > before; I refuse to pay thousands of dollars for something I might be > able to make myself; and most importantly I happened to come into the > possesion of a 6" x 1" piece. My ZEMAX catalog comes up with ng = 1.3969782, nF = 1.3949073, and nC = 1.39087680, making Pg,F = 0.5138. There is no glass in the Schott catalog close to this. What wavelengths were you considering? From donald_clement at yahoo.com Wed Jun 10 20:29:18 2009 From: donald_clement at yahoo.com (don clement) Date: Wed, 10 Jun 2009 04:29:18 -0700 (PDT) Subject: [ATM] Work report on the glass and foam blanks Message-ID: <171113.99365.qm@web34204.mail.mud.yahoo.com> Could the strange figure possibly be from the excellent insulation properties of the glass foam backing (Aerogel comes to mind http://en.wikipedia.org/wiki/Aerogel)where localized heating is occurring on the thin bonded layer when polishing? Don --- On Tue, 6/9/09, vorblesnak at peak.org wrote: > From: vorblesnak at peak.org > Subject: [ATM] Work report on the glass and foam blanks > To: atm at atmlist.net > Date: Tuesday, June 9, 2009, 9:06 PM > I wondered about your experience with > the figure on that blank you > have. I had a similar sort of figure on the 15.5 way back > when. It > was a wild swirl of hills and valleys that came from too > much heat > and pressure. Remember that glass was only 3/16ths when I > started. > > I wonder of you had some flexure in the adhesive layer? It > will > be interesting to see if you can pull it out. > > I've got a mild astigmatism starting in the fused glass and > foam > blank. I am not sure where it came from as I am polishing > on the > machine. I don't see any rocking action. I am polishing > with the > tool on top using a 12 inch lap. I have not trimmed the odd > warped > glass off of the outer edge and I wonder if it is rocking > the lap > as it moves. Could be where the hole in the middle came > from. I am > thinking it is time to trim that weird glass off and get > down to > the piece I am going to finish. That may solve a multitude > problems. > > I still have some good lines though. > > The Tessellated Blank ... > > I am through the 220 grit and getting ready to go to 320 > for a > while. I stopped for a while to put a flash polish on the > glass > to see what I had for figure. I have a polish out to the > 75% > zone, more or less. I get a good reflection of the > flashlight > across the pieces. That is a heartening thing. It suggests > the > pieces are at a very close focal length. I might try for a > street light refection with a 25mm eyepiece to see if I can > see > any detail at all. Just playing a bit before I move on to > the > next grit. > > I wore out the surface on the tool I was using. I am > thinking of > using a pie plate as a ring tool for my final grits. > > David Davis > Toledo, OR 97391 > > >From the experience that I've gotten with your blank, > DO NOT PUT > >ANY WEIGHT ON THE MIRROR or you will get a really > strange figure! > >If you want a polish and don't care about the figure, > put some > >weight on it and push fast.? You WILL get a really > strange figure > > > > >Bob May > > >rmay at nethere.com > >http: slash /nav.to slash bobmay > >http: slash /bobmay dot astronomy.net > > > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mjc5 at psu.edu Wed Jun 10 21:30:45 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Wed, 10 Jun 2009 08:30:45 -0400 Subject: [ATM] Work report on the glass and foam blanks In-Reply-To: <171113.99365.qm@web34204.mail.mud.yahoo.com> References: <171113.99365.qm@web34204.mail.mud.yahoo.com> Message-ID: On Jun 10, 2009, at 7:29 AM, don clement wrote: > > Could the strange figure possibly be from the excellent insulation > properties of the glass foam backing (Aerogel comes to mind http://en.wikipedia.org/wiki/Aerogel)where > localized heating is occurring on the thin bonded layer when > polishing? > I suspect that also. It is going to take that thing a good long while to stabilize, and until it does, look out. An example of this sort of thing, albeit with different things affecting it, is mounted posters. In many cases, the paper of the poster is mounted on a piece of "fome-core", a sandwich of paper and styrofoam. But the paper of the poster absorbs moisture at a different rate than the paper of the fome-core board. Warps badly under changing humidity. Some times the only cure is to mount another piece of the same type of poster paper on the back of the fome-core to balance the stresses. Different causes, but the same effect, that of unbalanced stresses, might be in play here. The top glass is cooling fairly quickly, but the foamed glass isn't. This might just be a case of waiting a few more hours to test. -73 de Mike N3LI - From vladimir.galogaza1 at zg.t-com.hr Thu Jun 11 01:23:42 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Wed, 10 Jun 2009 18:23:42 +0200 Subject: [ATM] Work report on the glass and foam blanks References: <171113.99365.qm@web34204.mail.mud.yahoo.com> Message-ID: >Could the strange figure possibly be from the excellent insulation >properties > of the glass foam backing (Aerogel comes to mind > http://en.wikipedia.org/wiki/Aerogel)where localized heating is occurring > on > the thin bonded layer when polishing? glass foam thermal diffusivity 4.4 10^-7 m^2/sec glass foam thermal conductivity (at 10 degrees C) 0.038 W/m K Glass thermal conductivity 0.2 W/m K glass foam specific heat 0.84 kJ/kg K glass specific heat. 49 J/mol K Glass foam density 100 kg/m^3 Glass density 2520 kg/m^3 Linear thermal expansion coefficient Glass foam 9*10^-6 /K Linear thermal expansion coefficient glass 9 *10^-6/K Foam backing is good thermal insulator (at least 10 times better than solid glass). But its density is 25 time smaller. Therefore amount of heat it contains, and must get rid of, is smaller. Gas bubbles within foam conduct the heat via convection which is more efficient that heat diffusion. It seems that overall thermal behavior is not so simply predictable from just one parameter only. We shall see more when first mirrors with foam backing will be tested for mechanical and thermal stability of their figure. Regards Vladimir. Regards Vladimir. From rflrs at verizon.net Thu Jun 11 03:42:46 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Wed, 10 Jun 2009 14:42:46 -0400 Subject: [ATM] Lithium Flouride Apo In-Reply-To: <4A2FDF4C.1070606@inreach.com> References: <4A2ED07E.7020703@inreach.com> <4A2F4BB6.3010706@verizon.net> <4A2FDF4C.1070606@inreach.com> Message-ID: <4A2FFEA6.3070409@verizon.net> Jan Bentz wrote: > > Richard -- I was considering the usual visual wavelengths between g & > r. But you are right, originally I had faulty index #'s for the LiF > but finally I got what I think is an accurate P f,e of .44417 and > could not get a good match even with FK-5. As you know very slight > differences in index with low dispersion glass will blow the match. > The closest one I could find is seawater! Maybe I'll see if I can > sell it to someone looking for a UV transmitting window. I already rejected the salt. Curious: LiF --> 0.44586, H2O --> 0.44458 Oh, well... From gfbrandenburg at yahoo.com Thu Jun 11 06:49:45 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Wed, 10 Jun 2009 14:49:45 -0700 (PDT) Subject: [ATM] [M-O-M] Horace Davis Message-ID: <479125.74252.qm@web111510.mail.gq1.yahoo.com> Congratulations to both of you, and kudos on your persistence! I know how much effort Horace has put into this. He hasn't given up yet! 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, 6/9/09, Tom Stokes wrote: > From: Tom Stokes > Subject: [M-O-M] Horace Davis > To: Mirror-O-Matic at yahoogroups.com, atm at atmlist.net > Date: Tuesday, June 9, 2009, 7:50 PM > I'm sure most of you have seen > Horace's posts on his attempts at casting > mirror blanks. He has been trying it for about a year and a > half now. I > offered to grind and strain test some of his blanks, and > about mid June, I > received a 15" x 1.5" Pyrex blank. This is a story of my > dealings with that > blank. > > http://www.mirrorgrindingmachine.com/horacedavis/ > > I'm sure it will make a very good mirror for someone. Maybe > me! > > Tom Stokes > > > > ------------------------------------ > > Community email addresses: > ? Post message: Mirror-O-Matic at onelist.com > ? Subscribe:? ? Mirror-O-Matic-subscribe at onelist.com > ? Unsubscribe:? Mirror-O-Matic-unsubscribe at onelist.com > ? List owner:???Mirror-O-Matic-owner at onelist.com > > Shortcut URL to this page: > ? http://www.onelist.com/community/Mirror-O-MaticYahoo! > Groups Links > > <*> To visit your group on the web, go to: > ? ? http://groups.yahoo.com/group/Mirror-O-Matic/ > > <*> Your email settings: > ? ? Individual Email | Traditional > > <*> To change settings online go to: > ? ? http://groups.yahoo.com/group/Mirror-O-Matic/join > ? ? (Yahoo! ID required) > > <*> To change settings via email: > ? ? mailto:Mirror-O-Matic-digest at yahoogroups.com > > ? ? mailto:Mirror-O-Matic-fullfeatured at yahoogroups.com > > <*> To unsubscribe from this group, send an email > to: > ? ? Mirror-O-Matic-unsubscribe at yahoogroups.com > > <*> Your use of Yahoo! Groups is subject to: > ? ? http://docs.yahoo.com/info/terms/ > > From rmay at nethere.com Thu Jun 11 07:11:05 2009 From: rmay at nethere.com (Bob May) Date: Wed, 10 Jun 2009 15:11:05 -0700 Subject: [ATM] Work report on the glass and foam blanks References: <49780.69.59.210.182.1244606793.squirrel@webmail.peak.org> Message-ID: <002601c9ea18$5a17e580$b1ff1345@amd> I'd not worry about the shape of the glass so much. I'd be more worried about the weight on the blank distorting the shape. FWIW, you can always make a thin backing/support for the blank by throwing down some pourable stone on the turntable (dont' forget a index to the table!) and put the blank on there so that nothing moves. What I last had was a grabbing at certain parts of the stroke. This generally indicates that the glass surface isn't spherical. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From kabukie at gmail.com Thu Jun 11 12:00:46 2009 From: kabukie at gmail.com (Chris Welsh) Date: Wed, 10 Jun 2009 23:00:46 -0400 Subject: [ATM] Ronchi Grating Question Message-ID: <1fb26e6f0906102000i49d02a62g5ad9c744e82a80a8@mail.gmail.com> Hi All, I am going to purchase a grating from edmund sci. to do a ronchi test on my 8" f/6, and am just wondering which grating is more suitable, the 5 lp/mm or 10 lp/mm? I know that 100 lines / inch is recommended, but how does this translate to 'line-pairs / mm'? -- Cheers, Chris Welsh IPTV / DTV Technical Specialist kabukie at gmail.com From tjfoster at xplornet.com Thu Jun 11 12:28:12 2009 From: tjfoster at xplornet.com (Ted & Joan Foster) Date: Wed, 10 Jun 2009 23:28:12 -0400 Subject: [ATM] Polishing with vacuum Message-ID: <4A3079CC.60006@xplornet.com> Bob May wrote, >From the experience that I've gotten with your blank, DO NOT PUT ANY WEIGHT ON THE MIRROR or you will get a really strange figure! If you want a polish and don't care about the figure, put some weight on it and push fast. You WILL get a really strange figure tho which will take some time to get worked out. There will be hills and valleys all over the place! They will not be concentric either! My experimenting with vacuum polishing to reduce print through may be of interest here. It remains to be seen if it can be used to make a smooth figure. Ted Foster From vorblesnak at peak.org Fri Jun 12 02:10:19 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Thu, 11 Jun 2009 10:10:19 -0700 (PDT) Subject: [ATM] Work report on the glass and foam blanks Message-ID: <13778.159.121.96.200.1244740219.squirrel@webmail.peak.org> But, isn't the lack of a spherical shape the shape of the glass? I found a strong astigmatism in the fused blank I am working. The lap moves well on the glass but I am seeing a non spherical surface at testing. Is it in the glass or in the technique? I don't think we can eliminate either as a source. The interaction between the two materials could also be a source. This is odd in a way as the fused blank is in theory a single piece of material. Yet it is two materials. It all almost sounds like babble, be we are seeing some interesting affects from our polishing. David Davis Toledo, OR 97391 > I'd not worry about the shape of the glass so much. I'd be more > worried about the weight on the blank distorting the shape. > FWIW, you can always make a thin backing/support for the blank by > throwing down some pourable stone on the turntable (dont' forget > a index to the table!) and put the blank on there so that nothing > moves. > What I last had was a grabbing at certain parts of the stroke. > This generally indicates that the glass surface isn't spherical. > Bob May > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net From vorblesnak at peak.org Fri Jun 12 02:38:25 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Thu, 11 Jun 2009 10:38:25 -0700 (PDT) Subject: [ATM] Horace Davis In-Reply-To: References: Message-ID: <10927.159.121.96.200.1244741905.squirrel@webmail.peak.org> An excellent piece of work by both of you and a good report. Well done. David Davis Toledo, OR 97391 > Subject: [ATM] Horace Davis > Message-ID: <130F5762A33842D1A068021C5AE55278 at tom> > Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > reply-type=original > > I'm sure most of you have seen Horace's posts on his attempts at casting > mirror blanks. He has been trying it for about a year and a half now. I > offered to grind and strain test some of his blanks, and about mid June, I > received a 15" x 1.5" Pyrex blank. This is a story of my dealings with > that > blank. > > http://www.mirrorgrindingmachine.com/horacedavis/ > > I'm sure it will make a very good mirror for someone. Maybe me! > > Tom Stokes > > > > ------------------------------ From rmay at nethere.com Fri Jun 12 04:49:53 2009 From: rmay at nethere.com (Bob May) Date: Thu, 11 Jun 2009 12:49:53 -0700 Subject: [ATM] Ronchi Grating Question References: <1fb26e6f0906102000i49d02a62g5ad9c744e82a80a8@mail.gmail.com> Message-ID: <000a01c9eacd$cad016c0$b29a5545@amd> The grating frequency isn't that important. The finer gratings just allow the grating to be closer to the focal point than a larger grating. With the quality of the Edmund gratings, I'd not worry about variations of the grating very much. Buy a cheap one as fine as you can get and accept for the price. It will work fine. Note that the way that it is often used, you need one that is large enough to get a LED and a micorlens behind it so you can see the results. FWIW, Willman-Bell still has some gratings that I've been using and finding to be quite acceptable and they are quite cheap. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Fri Jun 12 04:51:49 2009 From: rmay at nethere.com (Bob May) Date: Thu, 11 Jun 2009 12:51:49 -0700 Subject: [ATM] Polishing with vacuum References: <4A3079CC.60006@xplornet.com> Message-ID: <000e01c9eace$0f98bb40$b29a5545@amd> I'd figure that vacuum polishing would force the glass into a stressed shape and that would be nice if you are interested in doing an odd shape. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From atmer at flash.net Fri Jun 12 07:06:31 2009 From: atmer at flash.net (Anthony Stillman) Date: Thu, 11 Jun 2009 15:06:31 -0700 (PDT) Subject: [ATM] Ronchi Grating Question Message-ID: <546761.86350.qm@web82007.mail.mud.yahoo.com> ...The grating frequency isn't that important. I would add emphasis to "that." I've read a couple of papers in Applied Optics where would be professional optics people (i.e. academics) have foolishly used super fine (300 lpi) gratings thinking there's no difference. Their results were laughable. An amateur (someone who does things for the love of it) would have know better. There are limits to this form of lateral shearing interferometer (ronchi). Anthony From atmpob at yahoo.com Fri Jun 12 08:02:44 2009 From: atmpob at yahoo.com (Dale Eason) Date: Thu, 11 Jun 2009 16:02:44 -0700 (PDT) Subject: [ATM] Ronchi Grating Question Message-ID: <382268.47087.qm@web54503.mail.re2.yahoo.com> The grating frequency does matter. If it is too fine then diffraction effects become so pronounced the grating can not be used for what we want it to. If it is too coarse then it is not sensitive enough except to be used as a Foucault knife. 80 to 100 lpi is a good range. There is no need for a microlens. You just put your eye behind the grating. Bob I don't know what you are talking about in relation to a microlens and it's purpose. Can you explain? The orginal email asked what is the LPI equivalent of line pairs per millimeter. Bob did not answer that one, and I think it was the most important one. It will keep him from buying a grating that is too fine and thus useless. I think the conversion is to multiple the line paris per mm by 25.4 to get LPI. Dale Eason --- On Thu, 6/11/09, Bob May wrote: > From: Bob May > Subject: Re: [ATM] Ronchi Grating Question > To: atm at atmlist.net > Date: Thursday, June 11, 2009, 2:49 PM > The grating frequency isn't that > important.? The finer gratings > just allow the grating to be closer to the focal point than > a > larger grating.? With the quality of the Edmund > gratings, I'd not > worry about variations of the grating very much. > Buy a cheap one as fine as you can get and accept for the > price. > It will work fine.? Note that the way that it is often > used, you > need one that is large enough to get a LED and a micorlens > behind > it so you can see the results. > FWIW, Willman-Bell still has some gratings that I've been > using > and finding to be quite acceptable and they are quite > cheap. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From baldjeff at comcast.net Fri Jun 12 08:06:49 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Thu, 11 Jun 2009 16:06:49 -0700 Subject: [ATM] Ronchi Grating Question References: <382268.47087.qm@web54503.mail.re2.yahoo.com> Message-ID: <69A7C84CA0564F46A0A5FA28C52E924B@glendaspc> I think there is a good time to use a higher frequency than 100 lpi, that's when it is mounted into a lensless eyepiece and used on stars. I like my 130 lpi in scopes, but 85 lpi on my test stand. JB Jeff and Glenda Baldwin Lathrop, CA www.agetawaylogcabin.com www.stocktonastro.org The grating frequency does matter. If it is too fine then diffraction effects become so pronounced the grating can not be used for what we want it to. If it is too coarse then it is not sensitive enough except to be used as a Foucault knife. 80 to 100 lpi is a good range. From wkitty42 at windstream.net Fri Jun 12 08:48:48 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Thu, 11 Jun 2009 19:48:48 -0400 Subject: [ATM] Ronchi Grating Question In-Reply-To: <382268.47087.qm@web54503.mail.re2.yahoo.com> References: <382268.47087.qm@web54503.mail.re2.yahoo.com> Message-ID: <4A3197E0.6090005@windstream.net> Dale Eason wrote: > The orginal email asked what is the LPI equivalent of line pairs per millimeter. > Bob did not answer that one, and I think it was the most important one. It will > keep him from buying a grating that is too fine and thus useless. > > I think the conversion is to multiple the line paris per mm by 25.4 to get LPI. that's what my math tells me, too... so, 10 LPM = 254 LPI... -- _\/ (@@) 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 wa4guu at verizon.net Fri Jun 12 10:33:42 2009 From: wa4guu at verizon.net (Jerry) Date: Thu, 11 Jun 2009 21:33:42 -0400 Subject: [ATM] Ronchi Grating Question In-Reply-To: <000a01c9eacd$cad016c0$b29a5545@amd> Message-ID: I prefer 133 lpi but it doesn't matter too much from about 85 to 150 lpi or so. I talked with Willmann-Bell about 10 days ago. They no longer have 133 lpi gratings but do have 100 lpi gratings. Willmann-Bell now has their mirror making materials listed on their website, with the exception of their gratings. They no longer have a printed catalog. http://www.willbell.com/ATMSupplies/ATM_Supplies.htm 25.4 mm per inch so of the two choices mentioned... 5 lpmm = 127 lpi (this is the better choice in my opinion) 10 lpmm = 254 lpi Jerry ------Original Message----- From: Bob May Subject: Re: [ATM] Ronchi Grating Question FWIW, Willman-Bell still has some gratings that I've been using and finding to be quite acceptable and they are quite cheap. Bob May From richard1941 at gmail.com Fri Jun 12 11:34:27 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Thu, 11 Jun 2009 21:34:27 -0500 Subject: [ATM] Polishing with vacuum In-Reply-To: <000e01c9eace$0f98bb40$b29a5545@amd> References: <4A3079CC.60006@xplornet.com> <000e01c9eace$0f98bb40$b29a5545@amd> Message-ID: How is that different from the classical method of schmidt correctors? Sent from my iPhone On Jun 11, 2009, at 14:51, "Bob May" wrote: > I'd figure that vacuum polishing would force the glass into a > stressed shape and that would be nice if you are interested in > doing an odd shape. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From drgert1 at yahoo.com Fri Jun 12 12:25:23 2009 From: drgert1 at yahoo.com (Gert Gottschalk) Date: Thu, 11 Jun 2009 20:25:23 -0700 (PDT) Subject: [ATM] Ronchi Grating Question Message-ID: <747394.12083.qm@web45115.mail.sp1.yahoo.com> Hi, There are other interpretations possible as the technical term 'line pair' is not well chosen. Maybe someone can clarify. LPI : Lines Per Inch. Are we thinking of the 'black' stuff as the line? Then what about the 'white' in between? Case 1: We consider 'white paper' with black lines on it. Thus 10LPI describe 10 black lines per 1 inch on white paper. Each black line is 1/20inch wide (assuming for simplicity 50:50 duty cycle) Case 2: We consider white and black 'lines' abutting side-by-side with no gap in between to see the background underneath. 10LPI would then be 5 black and 5 white of such lines per 1 inch. Each black line would be 1/10inch wide. Each white line would be 1/10inch wide. (again assuming for simplicity 50:50 duty cycle) I find case 1 more convincing but have no original literature quote that confirms it is correct. LPM : Line Pairs per MM. Seems to imply an opposite point of view as the LPI case above. What is the definition of a line pair? Case 1: A line pair is made up of a black and a white line abutting each other with no gap in between to see the background underneath. 10LPM would then be 10 black and 10 white lines constituting 10 pairs of lines per MM. Each black line would be 1/20MM wide. Each white line would be 1/20MM wide. (again assuming for simplicity 50:50 duty cycle) Case 2: A line pair is made up of two black lines on a white background. So the 'stepping' unit would be 'black-white-black-white'. Now 10LPM would be 10 line pairs or 20 black lines and 20 white lines. Each black line would be 1/40MM wide. Each white line would be 1/40MM wide. (again assuming for simplicity 50:50 duty cycle) Again, I find case 1 more convincing but have no original literature quote that confirms it is correct. To convert one would have to sider the possible combinations of the above. And of course to do the math apply that 1 inch = 25.4 mm 1 mm = 0.0394 inch Enough splitting lines (ahhmm hair) Gert --- On Thu, 6/11/09, Dale Eason wrote: ... > The orginal email asked what is the LPI equivalent of line > pairs per millimeter.? Bob did not answer that one, and > I think it was the most important one.? It will keep > him from buying a grating that is too fine and thus > useless. > > I think the conversion is to multiple the line paris per mm > by 25.4 to get LPI. > > Dale Eason ... From rozer at pacbell.net Fri Jun 12 12:34:25 2009 From: rozer at pacbell.net (Richard Ozer) Date: Thu, 11 Jun 2009 20:34:25 -0700 Subject: [ATM] Ronchi Grating Question In-Reply-To: <747394.12083.qm@web45115.mail.sp1.yahoo.com> References: <747394.12083.qm@web45115.mail.sp1.yahoo.com> Message-ID: <4A31CCC1.2020202@pacbell.net> Gert, I think it's case #1. That is how our gratings at TMW appear, how the Edmunds gratings appear, and that's also how the postscript program we use to print gratings is coded. I don't think this is one of those "is a zebra a black animal with white stripes or a white animal with black stripes" question... RO Gert Gottschalk wrote: > Hi, > > There are other interpretations possible as the technical term 'line pair' is not well chosen. Maybe someone can clarify. > > LPI : Lines Per Inch. Are we thinking of the 'black' stuff as the line? Then what about the 'white' in between? > > Case 1: We consider 'white paper' with black lines on it. Thus 10LPI describe 10 black lines per 1 inch on white paper. Each black line is 1/20inch wide (assuming for simplicity 50:50 duty cycle) > Case 2: We consider white and black 'lines' abutting side-by-side with no gap in between to see the background underneath. 10LPI would then be 5 black and 5 white of such lines per 1 inch. Each black line would be 1/10inch wide. Each white line would be 1/10inch wide. (again assuming for simplicity 50:50 duty cycle) > > I find case 1 more convincing but have no original literature quote that confirms it is correct. > > LPM : Line Pairs per MM. Seems to imply an opposite point of view as the LPI case above. What is the definition of a line pair? > > Case 1: A line pair is made up of a black and a white line abutting each other with no gap in between to see the background underneath. 10LPM would then be 10 black and 10 white lines constituting 10 pairs of lines per MM. Each black line would be 1/20MM wide. Each white line would be 1/20MM wide. (again assuming for simplicity 50:50 duty cycle) > Case 2: A line pair is made up of two black lines on a white background. So the 'stepping' unit would be 'black-white-black-white'. Now 10LPM would be 10 line pairs or 20 black lines and 20 white lines. Each black line would be 1/40MM wide. Each white line would be 1/40MM wide. (again assuming for simplicity 50:50 duty cycle) > > Again, I find case 1 more convincing but have no original literature quote that confirms it is correct. > > To convert one would have to sider the possible combinations of the above. > > And of course to do the math apply that > 1 inch = 25.4 mm > 1 mm = 0.0394 inch > > Enough splitting lines (ahhmm hair) > Gert > > --- On Thu, 6/11/09, Dale Eason wrote: > ... > >> The orginal email asked what is the LPI equivalent of line >> pairs per millimeter. Bob did not answer that one, and >> I think it was the most important one. It will keep >> him from buying a grating that is too fine and thus >> useless. >> >> I think the conversion is to multiple the line paris per mm >> by 25.4 to get LPI. >> >> Dale Eason >> > ... > > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > > From richard at foucault.co.uk Fri Jun 12 19:18:09 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Fri, 12 Jun 2009 11:18:09 +0100 Subject: [ATM] Ronchi Grating Question In-Reply-To: <546761.86350.qm@web82007.mail.mud.yahoo.com> References: <546761.86350.qm@web82007.mail.mud.yahoo.com> Message-ID: <169324503.20090612111809@foucault.co.uk> Hello Anthony, Thursday, June 11, 2009, 11:06:31 PM, you wrote: > academics) have foolishly used super fine (300 lpi) gratings 300LPI = 11.8 lines per mm which is not out of the question at all , is it?. Were you thinking (or maybe meant) 300 lines per mm ? -- Best regards, Richard in the UK From foreilly at verizon.net Fri Jun 12 19:41:17 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Fri, 12 Jun 2009 06:41:17 -0400 Subject: [ATM] Ronchi Grating Question References: <546761.86350.qm@web82007.mail.mud.yahoo.com> <169324503.20090612111809@foucault.co.uk> Message-ID: Is the line the black bar (or the white bar), or the interface between them, that infinately thin but long line at which the stripes convert from black to white? Francis J. O'Reilly ----- Original Message ----- From: "Richard in the UK" To: "Anthony Stillman" Sent: Friday, June 12, 2009 6:18 AM Subject: Re: [ATM] Ronchi Grating Question > Hello Anthony, > > Thursday, June 11, 2009, 11:06:31 PM, you wrote: > >> academics) have foolishly used super fine (300 lpi) gratings > > 300LPI = 11.8 lines per mm which is not out of the question at all , is > it?. > Were you thinking (or maybe meant) 300 lines per mm ? > > -- > Best regards, > Richard in the UK > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From wa4guu at verizon.net Fri Jun 12 19:51:44 2009 From: wa4guu at verizon.net (Jerry) Date: Fri, 12 Jun 2009 06:51:44 -0400 Subject: [ATM] Ronchi Grating Question In-Reply-To: Message-ID: Take a white sheet of paper and draw two black vertical lines on it. How many lines did you draw? If you drew more than 2 you did not follow instructions. If you were making a picket fence...??? Jerry From Mitch_Bisnauth at Cknainc.com Fri Jun 12 21:46:07 2009 From: Mitch_Bisnauth at Cknainc.com (Mitch_Bisnauth at Cknainc.com) Date: Fri, 12 Jun 2009 07:46:07 -0500 Subject: [ATM] Ronchi Grating Question In-Reply-To: Message-ID: Jerry....this is not the Amature Picket Fence list....did you mis-post by chance ?? MitchB "Jerry" Sent by: atm-bounces at atmlist.net 06/12/2009 05:51 AM To "ATM list" cc Subject Re: [ATM] Ronchi Grating Question Take a white sheet of paper and draw two black vertical lines on it. How many lines did you draw? If you drew more than 2 you did not follow instructions. If you were making a picket fence...??? Jerry _______________________________________________ ATM mailing list http://www.atmlist.net/ From rmay at nethere.com Sat Jun 13 05:04:03 2009 From: rmay at nethere.com (Bob May) Date: Fri, 12 Jun 2009 13:04:03 -0700 Subject: [ATM] Ronchi Grating Question References: <382268.47087.qm@web54503.mail.re2.yahoo.com> Message-ID: <000c01c9eb98$efc08de0$bf985545@amd> Dale, the microlens I was talking about is the lens for a cheap security camera. You know I love those things as they allow me to see things without getting my eye down there in some odd place and occasionally see the view of interest. Now, after a couple of medical disasters, I need those cameras to be able to see things anymore. In addition, they make the views so nice and stable that you can spend the time contemplating the results of a test in progress quite comfortably. Also, guys, note that I said to by the cheap priced gratings. The prices for those, if you looked in the Edmund catalog do get quite expensive in the finer sizes. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Sat Jun 13 05:06:52 2009 From: rmay at nethere.com (Bob May) Date: Fri, 12 Jun 2009 13:06:52 -0700 Subject: [ATM] Ronchi Grating Question References: <747394.12083.qm@web45115.mail.sp1.yahoo.com> Message-ID: <001501c9eb99$548cb140$bf985545@amd> You can go either way. A line pair is a black and a clear stripe. On the other hand, a line per (whatever) is a black line. As a result, two different definitions are the same thing. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From b-hamburger at artinso.com Sat Jun 13 07:35:31 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Sat, 13 Jun 2009 00:35:31 +0200 Subject: [ATM] Ronchi Grating Question In-Reply-To: <000c01c9eb98$efc08de0$bf985545@amd> References: <382268.47087.qm@web54503.mail.re2.yahoo.com> <000c01c9eb98$efc08de0$bf985545@amd> Message-ID: <009501c9ebae$18ed1fc0$4ac75f40$@com> Bob, I am wondering about what type lens you would use for a camera setup, as described on your page. I guess it should be a bi-convex lens? How would you size it in order to cover a wide range of apertures and focal lengths? How would optical errors of the lens influence the test results? I am thinking about putting together a compact camera ronchi/focault tester, with a cheap webcam as imager and provisions made to easily swap different gratings/knife-edges. The idea is to fit it on a camera tripod and incorporate z-axis movement in the housing. Berthold > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Bob May > Sent: viernes, 12 de junio de 2009 22:04 > To: atm at atmlist.net > Subject: Re: [ATM] Ronchi Grating Question > > Dale, the microlens I was talking about is the lens for a cheap > security camera. You know I love those things as they allow me > to see things without getting my eye down there in some odd place > and occasionally see the view of interest. Now, after a couple > of medical disasters, I need those cameras to be able to see > things anymore. In addition, they make the views so nice and > stable that you can spend the time contemplating the results of a > test in progress quite comfortably. > Also, guys, note that I said to by the cheap priced gratings. > The prices for those, if you looked in the Edmund catalog do get > quite expensive in the finer sizes. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From tjfoster at xplornet.com Sat Jun 13 09:52:19 2009 From: tjfoster at xplornet.com (Ted & Joan Foster) Date: Fri, 12 Jun 2009 20:52:19 -0400 Subject: [ATM] polishing with vacuum Message-ID: <4A32F843.60701@xplornet.com> Richard, ... Schmidt created his vacuum in a pan under the plate to deform it while being figured. I'm applying the vacuum between the lap and mirror to generate the pressure required for polishing, i.e.. atmospheric pressure on the back of the lap and the back of the plate being polished Since the lap and mirror are in intimate contact, and I'm supporting all the weight of the lap and over arm with a bungee, there should be minimal distortion of the thin mirror, assuming the lap is properly cold pressed. Compare this to gluing on veneer. You can use clamps, not practical in our case, you can apply weights, which compares to what we do, or you can put it in a vacuum bag and let atmospheric pressure do the job for you. Hope this explains it better. Ted From tstokes at pacbell.net Sat Jun 13 11:50:28 2009 From: tstokes at pacbell.net (Tom Stokes) Date: Fri, 12 Jun 2009 19:50:28 -0700 Subject: [ATM] Ronchi Grating Question References: <382268.47087.qm@web54503.mail.re2.yahoo.com> <000c01c9eb98$efc08de0$bf985545@amd> Message-ID: <8126EDDB148545B1AE358AA83FBACB69@tom> > Also, guys, note that I said to by the cheap priced gratings. > The prices for those, if you looked in the Edmund catalog do get > quite expensive in the finer sizes. What happened to the idea of printing Ronchi lines on a sheet of acetate? I'm pretty sure a laser printer can do it but not sure if it is good enough. Don't know about ink jets. Tom Stokes ----- Original Message ----- From: "Bob May" To: Sent: Friday, June 12, 2009 1:04 PM Subject: Re: [ATM] Ronchi Grating Question > Dale, the microlens I was talking about is the lens for a cheap > security camera. You know I love those things as they allow me > to see things without getting my eye down there in some odd place > and occasionally see the view of interest. Now, after a couple > of medical disasters, I need those cameras to be able to see > things anymore. In addition, they make the views so nice and > stable that you can spend the time contemplating the results of a > test in progress quite comfortably. > Also, guys, note that I said to by the cheap priced gratings. > The prices for those, if you looked in the Edmund catalog do get > quite expensive in the finer sizes. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From richard at foucault.co.uk Sat Jun 13 19:52:24 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Sat, 13 Jun 2009 11:52:24 +0100 Subject: [ATM] polishing with vacuum In-Reply-To: <4A32F843.60701@xplornet.com> References: <4A32F843.60701@xplornet.com> Message-ID: <643362034.20090613115224@foucault.co.uk> Hello Ted, Saturday, June 13, 2009, 1:52:19 AM, you wrote: > I'm applying the vacuum between the lap > and mirror to generate the pressure required for polishing The 'normal' pressure for polishing is 0.5 PSI. It sounds like you are applying an abnormal polishing pressure. -- Best regards, Richard in the UK From blaktony86 at yahoo.com Sat Jun 13 22:52:40 2009 From: blaktony86 at yahoo.com (TONY B) Date: Sat, 13 Jun 2009 08:52:40 CDT Subject: [ATM] Ronchi Grating Question Message-ID: I dont understand either. You can print ronchi screens with a good laser printer and transparency paper. -----Original Message----- Date: Friday, June 12, 2009 9:51:32 pm To: "Bob May" ,atm at atmlist.net From: "Tom Stokes" Subject: Re: [ATM] Ronchi Grating Question > Also, guys, note that I said to by the cheap priced gratings. > The prices for those, if you looked in the Edmund catalog do get > quite expensive in the finer sizes. What happened to the idea of printing Ronchi lines on a sheet of acetate? I'm pretty sure a laser printer can do it but not sure if it is good enough. Don't know about ink jets. Tom Stokes ----- Original Message ----- From: "Bob May" To: Sent: Friday, June 12, 2009 1:04 PM Subject: Re: [ATM] Ronchi Grating Question > Dale, the microlens I was talking about is the lens for a cheap > security camera. You know I love those things as they allow me > to see things without getting my eye down there in some odd place > and occasionally see the view of interest. Now, after a couple > of medical disasters, I need those cameras to be able to see > things anymore. In addition, they make the views so nice and > stable that you can spend the time contemplating the results of a > test in From vorblesnak at peak.org Sun Jun 14 02:43:12 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Sat, 13 Jun 2009 10:43:12 -0700 (PDT) Subject: [ATM] The fused blank is broken Message-ID: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> I broke the fused glass and foam blank. Sometimes I think I break more glass than I finish. I was working on the astigmatism, trying some polishing techniques to true up the curve. I had the blank on the testing stand checking the results across several diameters. On the last test I rotated the blank and turned to walk back to the tester. About the time I was turning at the tester I heard it hit the concrete floor. I evidently didn't get it balanced before I let go of it. The impact took a chunk out of the glass and the foam. It cracked the glass across the middle of the blank nearly edge to edge. On the plus side the fused bond between glass and foam did not fail. I put it back on the stand and checked the figure. The two sides of the glass now have a completely different figure. The left is closer to corrected than the right hand side is. The crack is central enough that I think I can get two small mirrors out of the remains. I will work on the tessellated blank and see how it comes out. David Davis Toledo, OR 97391 From hermit at outofoptions.org Sun Jun 14 02:53:15 2009 From: hermit at outofoptions.org (hermit) Date: Sat, 13 Jun 2009 13:53:15 -0400 Subject: [ATM] The fused blank is broken In-Reply-To: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> References: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> Message-ID: <4A33E78B.10105@outofoptions.org> Nice variation on the fire hydrant method of dealing with stig. :D Ken Lowther vorblesnak at peak.org wrote: > I broke the fused glass and foam blank. Sometimes I think I break more > glass than I finish. I was working on the astigmatism, trying some > polishing techniques to true up the curve. I had the blank on the testing > stand checking the results across several diameters. On the last test I > rotated the blank and turned to walk back to the tester. About the time I > was turning at the tester I heard it hit the concrete floor. I evidently > didn't get it balanced before I let go of it. > > The impact took a chunk out of the glass and the foam. It cracked the > glass across the middle of the blank nearly edge to edge. On the plus side > the fused bond between glass and foam did not fail. I put it back on the > stand and checked the figure. The two sides of the glass now have a > completely different figure. The left is closer to corrected than the > right hand side is. > > The crack is central enough that I think I can get two small mirrors out > of the remains. > > I will work on the tessellated blank and see how it comes out. > > David Davis > Toledo, OR 97391 > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From baldjeff at comcast.net Sun Jun 14 03:02:04 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Sat, 13 Jun 2009 11:02:04 -0700 Subject: [ATM] The fused blank is broken References: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> Message-ID: <7BCDE42ACB4142E09EE56E3F9D252062@glendaspc> So sorry. I dropped my 24" f/3.7 blank about 0.5" from the test stand back in 1993, and it missed the plywood guard by a hair and went onto concrete, oystering the glass. I know your pain. I like your experimentation though, crap happens, and then you move on. Bald Jeff and Glenda Baldwin Lathrop, CA www.agetawaylogcabin.com www.stocktonastro.org ----- Original Message ----- From: To: Sent: Saturday, June 13, 2009 10:43 AM Subject: [ATM] The fused blank is broken >I broke the fused glass and foam blank. Sometimes I think I break more > glass than I finish. I was working on the astigmatism, trying some > polishing techniques to true up the curve. I had the blank on the testing > stand checking the results across several diameters. On the last test I > rotated the blank and turned to walk back to the tester. About the time I > was turning at the tester I heard it hit the concrete floor. I evidently > didn't get it balanced before I let go of it. > > The impact took a chunk out of the glass and the foam. It cracked the > glass across the middle of the blank nearly edge to edge. On the plus side > the fused bond between glass and foam did not fail. I put it back on the > stand and checked the figure. The two sides of the glass now have a > completely different figure. The left is closer to corrected than the > right hand side is. > > The crack is central enough that I think I can get two small mirrors out > of the remains. > > I will work on the tessellated blank and see how it comes out. > > David Davis > Toledo, OR 97391 > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From arjan.te.marvelde at hetnet.nl Sun Jun 14 03:09:45 2009 From: arjan.te.marvelde at hetnet.nl (Arjan te Marvelde (hetnet)) Date: Sat, 13 Jun 2009 20:09:45 +0200 Subject: [ATM] Ronchi Grating Question In-Reply-To: References: Message-ID: <4A33EB69.9070805@hetnet.nl> Ahh, c'mon Case 3: pattern {1 black, 2white and 1 black line} repeated, assuming lines are equally wide. Case 4: etc To cut things short, I think it's better to speak of line frequency... line being the elementary shape that is being repeated. >>> Case 1: We consider 'white paper' with black lines on it. Thus 10LPI describe 10 black lines per 1 inch on white paper. Each black line is 1/20inch wide (assuming for simplicity 50:50 duty cycle) Case 2: We consider white and black 'lines' abutting side-by-side with no gap in between to see the background underneath. 10LPI would then be 5 black and 5 white of such lines per 1 inch. Each black line would be 1/10inch wide. Each white line would be 1/10inch wide. (again assuming for simplicity 50:50 duty cycle) I find case 1 more convincing but have no original literature quote that confirms it is correct. LPM : Line Pairs per MM. Seems to imply an opposite point of view as the LPI case above. What is the definition of a line pair? Case 1: A line pair is made up of a black and a white line abutting each other with no gap in between to see the background underneath. 10LPM would then be 10 black and 10 white lines constituting 10 pairs of lines per MM. Each black line would be 1/20MM wide. Each white line would be 1/20MM wide. (again assuming for simplicity 50:50 duty cycle) Case 2: A line pair is made up of two black lines on a white background. So the 'stepping' unit would be 'black-white-black-white'. Now 10LPM would be 10 line pairs or 20 black lines and 20 white lines. Each black line would be 1/40MM wide. Each white line would be 1/40MM wide. (again assuming for simplicity 50:50 duty cycle) Again, I find case 1 more convincing but have no original literature quote that confirms it is correct. From richard at foucault.co.uk Sun Jun 14 06:05:41 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Sat, 13 Jun 2009 22:05:41 +0100 Subject: [ATM] Ronchi Grating Question In-Reply-To: <4A33EB69.9070805@hetnet.nl> References: <4A33EB69.9070805@hetnet.nl> Message-ID: <1114540413.20090613220541@foucault.co.uk> Hello Arjan, Saturday, June 13, 2009, 7:09:45 PM, you wrote: > Case 1: It's not rocket science!. 10 LPI means 10 black lines and 10 white spaces in each inch, i.e., the width of (1 black line + 1 white space) = 0.1" . The (black line + white space) is sometimes called a line pair. -- Best regards, Richard in the UK From rmay at nethere.com Sun Jun 14 07:32:54 2009 From: rmay at nethere.com (Bob May) Date: Sat, 13 Jun 2009 15:32:54 -0700 Subject: [ATM] Ronchi Grating Question References: <382268.47087.qm@web54503.mail.re2.yahoo.com> <000c01c9eb98$efc08de0$bf985545@amd> <009501c9ebae$18ed1fc0$4ac75f40$@com> Message-ID: <000601c9ec76$e540e020$a9fe1345@amd> The interesting thing is that the focal length of the lens is related to the focal ratio of the optic under test. The thing here is that you want a lens that has an angle to the imager of something a little bit more than the angle of the object (the optic under test) and the focal ratio is the angle measurement (after a fashion) of the optic. I have a lens of about 1" focal length on my first tester and that seems to work fine down to about F4 and up to about F10 (needless to say, with a much smaller image) For F2 or so, I'd probably be using a 1/2" or even less focal length lens for the camera. Since you're doing a single color of light, there is no need for a chromatically correct lens, just focus for that color! Lens shape should be a plano-convex lens with the convex side away from the imager according to lens theory. The smaller you get the spacing between the lens surface and the tester's test point (KE or grating), the smaller the physical image size is and thus the smaller the lens can be. You know this from trying to use a KE with the eye far behind the KE - you just don't see the light all the way across the optic under test! Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Sun Jun 14 07:42:26 2009 From: rmay at nethere.com (Bob May) Date: Sat, 13 Jun 2009 15:42:26 -0700 Subject: [ATM] Ronchi Grating Question References: Message-ID: <000f01c9ec78$3a205d40$a9fe1345@amd> Lets say you have a laser printer that can do 1200dpi. You want to do a 100lpi grating. First problem is that a line is going to be 6 dots wide. Not all that many dots to get resolution. Second is that (from my memory of doing some software for a laser printer) the dot will only be within a location of 40% of the nominal size of the dot. In addition, the dot size can vary by about 50% of nominal size. What the above actually says is that that 6 dot wide line will be extremely rough in its actual size and straightness. A Ronchi grating needs to have nice sharp straight edges to work well. You don't get these characteristics with a printer! It would be a lot better to take a wall and paint stripes on it and use a camera to photograph those lines. Not great but better than what you can do with a laser printer. In addition, you can get a much wider range of line widths without doing anything more than changine the distance from the wall. Using the right films and using better cameras than the 35mm will be the next step up. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From atmer at flash.net Sun Jun 14 09:14:25 2009 From: atmer at flash.net (Anthony Stillman) Date: Sat, 13 Jun 2009 17:14:25 -0700 (PDT) Subject: [ATM] Ronchi Grating Question Message-ID: <876168.92598.qm@web82006.mail.mud.yahoo.com> ...6 dots wide.? ...dot size ...paint stripes ...to photograph I've had good luck with laser printers and an old version of Canvas. Even with a 300 dpi printer, so long as I was careful with line placement and width (took a few tries), everything worked out fine. I've been able to make inverse ronchi-s straight from a 1200 dpi printer so so, but I found it was better to photo copy reduce them after printing them larger. Photo copiers may (probably will) induce distortion. Keep the image in the center. As for painting stripes, I once used a dot matrix printer then used my analog camera to take pictures on film. That was back when programs were stored on punch cards. Anthony From colja at internode.on.net Sun Jun 14 09:29:13 2009 From: colja at internode.on.net (Mike Colja) Date: Sun, 14 Jun 2009 10:29:13 +1000 Subject: [ATM] Ronchi Grating Question In-Reply-To: <1fb26e6f0906102000i49d02a62g5ad9c744e82a80a8@mail.gmail.com> Message-ID: <7tpfp5$b6hlao@ipmail01.adl6.internode.on.net> I have printed on a laser jet 100 lines per inch on plastic and it worked just fine, didn't give as much detail as the Edmund, but I could mount it on A slide with the knife and just slide it in and out as required. -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Chris Welsh Sent: Thursday, 11 June 2009 1:01 PM To: atm at atmlist.net Subject: [ATM] Ronchi Grating Question Hi All, I am going to purchase a grating from edmund sci. to do a ronchi test on my 8" f/6, and am just wondering which grating is more suitable, the 5 lp/mm or 10 lp/mm? I know that 100 lines / inch is recommended, but how does this translate to 'line-pairs / mm'? -- Cheers, Chris Welsh IPTV / DTV Technical Specialist kabukie at gmail.com _______________________________________________ ATM mailing list http://www.atmlist.net/ From nilsolof.carlin at telia.com Sun Jun 14 21:49:50 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Sun, 14 Jun 2009 14:49:50 +0200 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd> Message-ID: <7F87286500D843538529A4E8A9ED6A6C@dittda7685d135> > What the above actually says is that that 6 dot wide line will be > extremely rough in its actual size and straightness. A Ronchi > grating needs to have nice sharp straight edges to work well. With the common method of illumination through the Ronchi grid, using a fairly wide light source (such as a LED), what you see is not the image of particular lines, but a composite image of many lines superimposed, averaged both horizontally and vertically. By averaging, the lines will look clear and straight, despite local irregularities of each line (that would be revealed by using a true point source of light). Nils Olof From rmay at nethere.com Mon Jun 15 06:16:05 2009 From: rmay at nethere.com (Bob May) Date: Sun, 14 Jun 2009 14:16:05 -0700 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd> <7F87286500D843538529A4E8A9ED6A6C@dittda7685d135> Message-ID: <001701c9ed35$548c4be0$b5fe1345@amd> Nils, the lines will also be quite fuzzy. Good straight lines are going to do a much better job of contrast. I will agree tho that if there is nothing else, a laser print will indeed work to some degree. However, for the price of about $3.50 or so, the Willmann Bell grating will be a lot better. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From atmer at flash.net Mon Jun 15 07:43:26 2009 From: atmer at flash.net (Anthony Stillman) Date: Sun, 14 Jun 2009 15:43:26 -0700 (PDT) Subject: [ATM] Ronchi Grating Question Message-ID: <711619.90795.qm@web82004.mail.mud.yahoo.com> ...However, for the price Bob, Why would anyone for less than the cost of a Mc-meal want to use a quality grating when they could in a mere matter of days be able to struggle along with something half-assed. I mean really Bob, what's happened to your ATM instinct? You and your clear headed thinking are going to ruin it for all the newbes. Anthony From blaktony86 at yahoo.com Mon Jun 15 09:35:05 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Sun, 14 Jun 2009 17:35:05 -0700 (PDT) Subject: [ATM] The fused blank is broken Message-ID: <864461.46191.qm@web81907.mail.mud.yahoo.com> I am sorry for your incident! I can feel your pain. I once dropped a perfectly fine 6" telescope mirror (after 40hours+ of hand grinding, polishing, figuring on the floor) into a glass dish of silvering solution because my suction came off. This left a huge crater into the side of my mirror (optical surface included). This was my first mirror. However I did not give up and as you know and still making mirrors. I hope your tesselated blank comes out as well as we all hope it does. We need a breakthrough in the atm world on big mirrors. Hopefully its possible to see an optically perfect mirror from such a combination (glass foam + hexagonal glass). Keep at it, -Tony --- On Sat, 6/13/09, vorblesnak at peak.org wrote: From: vorblesnak at peak.org Subject: [ATM] The fused blank is broken To: atm at atmlist.net Date: Saturday, June 13, 2009, 12:43 PM I broke the fused glass and foam blank. Sometimes I think I break more glass than I finish. I was working on the astigmatism, trying some polishing techniques to true up the curve. I had the blank on the testing stand checking the results across several diameters. On the last test I rotated the blank and turned to walk back to the tester. About the time I was turning at the tester I heard it hit the concrete floor. I evidently didn't get it balanced before I let go of it. The impact took a chunk out of the glass and the foam. It cracked the glass across the middle of the blank nearly edge to edge. On the plus side the fused bond between glass and foam did not fail. I put it back on the stand and checked the figure. The two sides of the glass now have a completely different figure. The left is closer to corrected than the right hand side is. The crack is central enough that I think I can get two small mirrors out of the remains. I will work on the tessellated blank and see how it comes out. David Davis Toledo, OR 97391 _______________________________________________ ATM mailing list http://www.atmlist.net/ From foreilly at verizon.net Mon Jun 15 10:55:30 2009 From: foreilly at verizon.net (Francis J. O'Reilly) Date: Sun, 14 Jun 2009 21:55:30 -0400 Subject: [ATM] I cried Message-ID: I took a couple of my kids, Elizabeth, my young ATM and Seamus for a road trip yesterday. We went to pick up a drill press that I purchased on Ebay from a gentleman in Westchester, PA. When we were done, we took a ride over to "The Franklin" to see the Galileo exhibit. I had been to the museum once since it was remodeled, but just pretty much long enough to let the kids ride the train in the basement. Yesterday was quite another matter. The Galileo/Medici exhibit was great. As many of you know, one of Galileo's telescopes is on display until early September. My twelve year old son Seamus, who is profoundly autistic, and therefore always the happiest and most mischevious guy in any room, proved to me that if you don't have too much pride, you can get down on the floor and look through the lexan case and into the eyepiece end of the telescope (At the ceiling of the room). I did so after he was done. The field of view is incredibly narrow! The magnification is about three power and there is Galileo's handwriting on the end of the telescope which I am told proves that it was Galileo's. The other exhibits were generally neat with navagation equipment preceding Galileo's telescope and optics afterwards. It cost a little over $20.00 per person to get in, but that included a planetarium show and a "Sci-pass" which got us in to most of the rest of the museum. The Star Trek Exhibit was extra and much to Elizabeth's fourteen year old chargrin we passed on it. Given we got about four hours of entertainment and a lifetime of stories from the trip, it was well worth the $20.00 per pperson and the trip from NY. (The Yankees lost anyway) One note of caution, "Ben's Bistro" the museum's contract restaurant was exceptionally expensive, with sandwiches that I would pay $4.00 for on the outside going for over $8.00. Why then did I cry? At the end of my visit, we went to the Fels planetarium for the show, "Two Small Pieces of Glass" It was a nice movie for the kids. When we left, I noted a 24 inch convertable Cassegrain/Newtonian outside the planetarium. It was set up as an exhibit, in the basement where it cannot be used as a telescope. I understand why the museum can no longer use the telescope, light pollution has taken over Philadelphia many years ago,. but it was painful to see it sitting there not being used. I hope that someday it will once again be installed somewhere and returned to productive use. Francis J. O'Reilly From mjc5 at psu.edu Mon Jun 15 23:19:28 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 15 Jun 2009 10:19:28 -0400 Subject: [ATM] The fused blank is broken In-Reply-To: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> References: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> Message-ID: <7ECE7A35-5A58-44C9-B8A9-3F8CB94E6732@psu.edu> On Jun 13, 2009, at 1:43 PM, vorblesnak at peak.org wrote: > I broke the fused glass and foam blank. Arrrgh! So Sorry David... I've found that when breaking important glass, (I once dropped and broke an 8 inch piece of Optical glass that I was going to turn into a nice big refractor lens) one must make a sacrifice to the Holy Photons. 1. Get a bottle of Cuervo Gold 2. Pour 2 shot glasses with the tequila 3. pour one on the broken mirror or lens 4. Partake of the other shot - neat, no ice nor chaser allowed 5. Mutter a few words about the first light that never happened 6. Repeat as needed. note: if desired, you can substitute Makers Mark or Bombay Sapphire - it just has to be premium stuff. Do not work on your other mirror until the effects of the sacrifice wear off. -73 de Mike N3LI - From Mitch_Bisnauth at Cknainc.com Mon Jun 15 23:26:29 2009 From: Mitch_Bisnauth at Cknainc.com (Mitch_Bisnauth at Cknainc.com) Date: Mon, 15 Jun 2009 09:26:29 -0500 Subject: [ATM] Broken blank sacrifice In-Reply-To: <7ECE7A35-5A58-44C9-B8A9-3F8CB94E6732@psu.edu> Message-ID: well said....amen..... 7. Place order for replacement blank whilst spirit of sacrifice is around, (helps to ward of evil from new blank....!!) :-) From jhissong at gmail.com Mon Jun 15 23:27:29 2009 From: jhissong at gmail.com (Jason Hissong) Date: Mon, 15 Jun 2009 10:27:29 -0400 Subject: [ATM] The fused blank is broken In-Reply-To: <7ECE7A35-5A58-44C9-B8A9-3F8CB94E6732@psu.edu> References: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> <7ECE7A35-5A58-44C9-B8A9-3F8CB94E6732@psu.edu> Message-ID: This reminds me of Brashear's tale of the 12" mirror he was working on broke. He was pretty down about it and when he came home from work, he saw that his wife cleaned up the shop, got the boiler going, and the other blank ready to be worked. Brashear didn't drink, but you can feel his dismay of such an event. (I would go with Crown Royal myself and use the bag for the secondary cover as part of the ritual.. hehehehe) Jason Hissong http://undermidnight.blogspot.com http://www.undermidnight.com http://www.n8xe.com http://www.jasonhissong.com (BTW.. I am N8XE, good to see other hams doing atm stuff too!) On Mon, Jun 15, 2009 at 10:19 AM, Michael Coslo wrote: > I've found that when breaking important glass, ?(I once dropped and broke an > 8 inch piece of Optical glass that I was going to turn into a nice big > refractor lens) one must make a sacrifice to the Holy Photons. > > 1. Get a bottle of Cuervo Gold > > 2. Pour 2 shot glasses with the tequila > > 3. pour one on the broken mirror or lens > > 4. Partake of the other shot - neat, no ice nor chaser allowed > > 5. Mutter a few words about the first light that never happened > > 6. Repeat as needed. > > note: if desired, you can substitute Makers Mark or Bombay Sapphire - it > just has to be premium stuff. ?Do not work on your other mirror until the > effects of the sacrifice wear off. > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mcaramb at rocketmail.com Tue Jun 16 00:20:43 2009 From: mcaramb at rocketmail.com (Mike Carambat) Date: Mon, 15 Jun 2009 08:20:43 -0700 (PDT) Subject: [ATM] Ronchi Grating Question Message-ID: <373798.53252.qm@web50106.mail.re2.yahoo.com> Found instructions on DIY Ronchi screens on the internet some time back but have lost the link. It acutally works quite well and makes better, more pronounced shadows than the ones from Edmund! I used it to test one of those stupid 8" "parabolic" primary mirrors they sell on Ebay. As I suspected, they were actually quite spherical, not parabolic at all. You make the Ronchi gratings by cutting out two bars of 1/8" thick x 1.5" wide aluminum strap to about 3" long and tape them together. Then you drill a 1" hole in the middle through both bars. Now you've got two plates of aluminum with a hole in the middle, still taped together. Now for the fun bit. You get two spools of ultra-light gauge monofiliment from the Walmart thread and crafts department (sorry, can't remember the gauge... I think it was 00, but not sure), spool off a few inches from each spool and hold the threads side-by-side. tape them down about 1/8" from the left side of the hole at the edge of the bottom of the bar. Then begin wrapping your (still taped together) bars of aluminum about with the two threads, holding both spools in your hand or make rig to hold the spools and turn the bar instead. Go round and round, perpendicular to the edge of the bars, two threads at a time, side by side until you've made it completely across the hole and about 1/8" to the right of the hole. This sounds easy, but is very time consuming and requires a bit of dexterity. I think it took me about 45-60 minutes. The monofilment is hard to keep aligned as you work. I can't tell you how many times I had to back up and start over. You should end of with a perfect row of threads on both sides which do not overlap and do not have many gaps between them (a few is ok, don't drive yourself completely nuts). Now for the brilliant bit. Tape the end of one of the threads to the bar. Take the other thread and UNWRAP it. This will leave a thread-wide gap between each of the other threads. Ta-da! Use superglue or some other penetrating adhesive all around the holes on both sides of your aluminum bars, coating the threads well. When dry, simply cut through the threads and the tape along the edges of the bars to seperate the two finished pieces. The glue will hold the threads in place (hopefully). Now you've got two near exactly similiar Ronchi screens! IMPORTANT NOTES: Try not to put too much tension on your wrappings. I found that once the two plates were seperated at the end, the tension on the threads really pulled at the glue and seperated them enmass from the aluminum in a bunch at a few spots. I had to reseal it a few more times with more glue. It could also be that aluminium simply isn't a good surface to adhere monofilment to with superglue. Maybe something else, maybe 1/8" plywood or even heavy cardboard. Dunno, experiment. Hope this helps! From richard1941 at gmail.com Tue Jun 16 07:47:40 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Mon, 15 Jun 2009 18:47:40 -0400 Subject: [ATM] Ronchi Grating Question In-Reply-To: <7F87286500D843538529A4E8A9ED6A6C@dittda7685d135> References: <000f01c9ec78$3a205d40$a9fe1345@amd> <7F87286500D843538529A4E8A9ED6A6C@dittda7685d135> Message-ID: There are two ways of ronchi testing. One way is to have a point source and put the grating in the light cone. The other way is to have an extended light source with the light passing twice through the grating. Sent from my iPhone On Jun 14, 2009, at 8:49, "Nils Olof Carlin" wrote: >> What the above actually says is that that 6 dot wide line will be >> extremely rough in its actual size and straightness. A Ronchi >> grating needs to have nice sharp straight edges to work well. > > > With the common method of illumination through the Ronchi grid, > using a fairly wide light source (such as a LED), what you see is > not the image of particular lines, but a composite image of many > lines superimposed, averaged both horizontally and vertically. By > averaging, the lines will look clear and straight, despite local > irregularities of each line (that would be revealed by using a true > point source of light). > > Nils Olof > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From wkitty42 at windstream.net Tue Jun 16 09:22:57 2009 From: wkitty42 at windstream.net (waldo kitty) Date: Mon, 15 Jun 2009 20:22:57 -0400 Subject: [ATM] The fused blank is broken In-Reply-To: References: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> <7ECE7A35-5A58-44C9-B8A9-3F8CB94E6732@psu.edu> Message-ID: <4A36E5E1.6020609@windstream.net> Jason Hissong wrote: > This reminds me of Brashear's tale of the 12" mirror he was working on > broke. He was pretty down about it and when he came home from work, > he saw that his wife cleaned up the shop, got the boiler going, and > the other blank ready to be worked. it this story published on the web anywhere? it sounds like it would make for decent reading ;) -- _\/ (@@) 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 Tue Jun 16 11:49:31 2009 From: rmay at nethere.com (Bob May) Date: Mon, 15 Jun 2009 19:49:31 -0700 Subject: [ATM] Ronchi Grating Question References: <711619.90795.qm@web82004.mail.mud.yahoo.com> Message-ID: <000801c9ee2d$13a21c60$68ff1345@amd> It is a burden I must bear! Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From nilsolof.carlin at telia.com Tue Jun 16 18:41:21 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Tue, 16 Jun 2009 11:41:21 +0200 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd> <7F87286500D843538529A4E8A9ED6A6C@dittda7685d135> Message-ID: <2015F9C887DC45F39DABF13D249AE59A@dittda7685d135> Richard, yes, but why bother? A Ronchi grid may be helpful for detecting zones or roughness (including a turned edge), but sweeping a Foucault knife-edge across the field will give the same information (and with no diffraction grating side-effects). But it is of doubtful value for figuring. With diligence, you *can* extract zonal information by measuring the positions of the bands, and process it with SIXTESTS, but who does? It may show when you have polished to a decent sphere, but "pattern-matching" by eye is bound to fail (for an explanation, see Suiter's Star Testing...). A rough grid will appear "quite fuzzy" with diffuse lighting - but even the best Ronchi bands look fuzzy, and who can tell the difference without a good grid to compare with? Nils Olof ----- Original Message ----- From: "Richard Schwartz" To: "Nils Olof Carlin" Cc: "Bob May" ; Sent: Tuesday, June 16, 2009 12:47 AM Subject: Re: [ATM] Ronchi Grating Question > There are two ways of ronchi testing. One way is to have a point source > and put the grating in the light cone. The other way is to have an > extended light source with the light passing twice through the grating. > > Sent from my iPhone > > On Jun 14, 2009, at 8:49, "Nils Olof Carlin" > wrote: > >>> What the above actually says is that that 6 dot wide line will be >>> extremely rough in its actual size and straightness. A Ronchi >>> grating needs to have nice sharp straight edges to work well. >> >> >> With the common method of illumination through the Ronchi grid, using a >> fairly wide light source (such as a LED), what you see is not the image >> of particular lines, but a composite image of many lines superimposed, >> averaged both horizontally and vertically. By averaging, the lines will >> look clear and straight, despite local irregularities of each line (that >> would be revealed by using a true point source of light). >> >> Nils Olof >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > From stainless_steel at suddenlink.net Tue Jun 16 19:42:56 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 05:42:56 -0500 Subject: [ATM] ATM: Eric Mobsby Message-ID: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> Who remembers Eric Mobsby's brilliant improvement to Ronchi? I do; guess it just shows how old I am. D-LZ130 From lopez at mv.mv.com Tue Jun 16 20:29:02 2009 From: lopez at mv.mv.com (Lawrence D. Lopez) Date: Tue, 16 Jun 2009 07:29:02 -0400 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> Message-ID: <4A3781FE.5050804@mv.mv.com> *: What was it ? Larry stainless_steel at suddenlink.net wrote: > Who remembers Eric Mobsby's brilliant improvement to Ronchi? > > I do; guess it just shows how old I am. > D-LZ130 > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From foreilly at bestweb.net Tue Jun 16 21:05:17 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Tue, 16 Jun 2009 08:05:17 -0400 Subject: [ATM] ATM: Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> Message-ID: <0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> Who could forget the Mosby null test. Willman Bell is now out of the patterns. The Mosby null test created a pattern of curved Ronchi lines which when viewed in a Ronchi test would appear straight if the surface was properly corrected, thereby creating a null test. David, you're not too old. I remembered this and I'm only 51. Francis J. O'Reilly ----- Original Message ----- From: To: "ATM list" Sent: Tuesday, June 16, 2009 6:42 AM Subject: [ATM] ATM: Eric Mobsby > Who remembers Eric Mobsby's brilliant improvement to Ronchi? > > I do; guess it just shows how old I am. > D-LZ130 > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From richard at foucault.co.uk Tue Jun 16 22:07:00 2009 From: richard at foucault.co.uk (Richard in the UK) Date: Tue, 16 Jun 2009 14:07:00 +0100 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> <0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> Message-ID: <1357820178.20090616140700@foucault.co.uk> Hello Francis, Tuesday, June 16, 2009, 1:05:17 PM, you wrote: > Who could forget the Mosby null test. Willman Bell is now out of the > patterns. I believe there is a program for printing the pattern for a given mirror. -- Best regards, Richard in the UK From stainless_steel at suddenlink.net Tue Jun 16 23:01:02 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 09:01:02 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: References: Message-ID: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> Sky Publishing thought it was beyond clever; beyond the deep blue sea. Ran a series of articles, if I remember correctly. Just wondered how a thread so long about Ronchi could leave good old Eric out. D-LZ130 P.S.- As I understand it, the custom grating will give you straight lines when you have the glass right. ----- Original Message ----- From: To: Sent: Tuesday, June 16, 2009 6:25 AM Subject: Re: [ATM] ATM: Eric Mobsby > > I think last I checked, Willmann-Bell were still selling custom gratings. > Send them your mirror diameter and radius of curvature and they print a > grating. > Haven't tried it myself. Is it as easy as they say? > Brian > > > On Tue, 16 Jun 2009 stainless_steel at suddenlink.net wrote: > >> Who remembers Eric Mobsby's brilliant improvement to Ronchi? >> >> I do; guess it just shows how old I am. D-LZ130 >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From stainless_steel at suddenlink.net Tue Jun 16 23:04:02 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 09:04:02 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <4A3781FE.5050804@mv.mv.com> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> <4A3781FE.5050804@mv.mv.com> Message-ID: Lawrence, are you asking what your little plaintext illustration is, or what is an inverted Mobsby grating? A little confusion here. Can't send you a plain text illustration. Google Eric Mobsby or Mobnsby Ronchi test, et.al., etc. D-LZ130 ----- Original Message ----- From: "Lawrence D. Lopez" To: Cc: "ATM list" Sent: Tuesday, June 16, 2009 6:29 AM Subject: Re: [ATM] ATM: Eric Mobsby > *: > > What was it ? > Larry > > stainless_steel at suddenlink.net wrote: >> Who remembers Eric Mobsby's brilliant improvement to Ronchi? >> >> I do; guess it just shows how old I am. >> D-LZ130 >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ >> > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From stainless_steel at suddenlink.net Tue Jun 16 23:16:03 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 09:16:03 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> <0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> Message-ID: Ha! I've got a decade on you, "old son". I had a brilliant friend who lived in Chino Valley, AZ (yes- not the one in the Peoples' Republik of Kalifornia) who made nearly perfect mirrors. I just remembered his mailing address after much subconscious effort; it was he who first exposed me to the term "old son". He once carried (actually carried onto the airplane, a big Boeing) a 10" mirror and tool, wrapped together; I warned him (he ALWAYS got TDE and had to work it out, much tediousness) that my optical lab had a TUE virus in it, and he would have it when he left. He had it. Only in Okrahoma. The big ships just flew over Okrahoma. Wonder if anyone looked down at the tumbleweeds and red dirt? Good to see a thread about Mobsby's idea of how Ronchi should work. And I am the guy who threw the monkey wrench into the works. My father's brother, now in his 90s, saw the original Graf Zeppelin D-LZ127 fly over Okrahoma. The first aircraft to exceed one mega mile in service, and circumnavigate the globe. D-LZ130 ----- Original Message ----- From: "Francis J. O'Reilly" To: ; "ATM list" Sent: Tuesday, June 16, 2009 7:05 AM Subject: Re: [ATM] ATM: Eric Mobsby > Who could forget the Mosby null test. Willman Bell is now out of the > patterns. > > The Mosby null test created a pattern of curved Ronchi lines which when > viewed in a Ronchi test would appear straight if the surface was properly > corrected, thereby creating a null test. > > David, you're not too old. I remembered this and I'm only 51. > > Francis J. O'Reilly > ----- Original Message ----- > From: > To: "ATM list" > Sent: Tuesday, June 16, 2009 6:42 AM > Subject: [ATM] ATM: Eric Mobsby > > >> Who remembers Eric Mobsby's brilliant improvement to Ronchi? >> >> I do; guess it just shows how old I am. >> D-LZ130 >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From Harro.Treur at waternet.nl Tue Jun 16 23:21:59 2009 From: Harro.Treur at waternet.nl (Harro Treur) Date: Tue, 16 Jun 2009 16:21:59 +0200 Subject: [ATM] Betr.: Re: ATM: Eric Mobsby In-Reply-To: <1357820178.20090616140700@foucault.co.uk> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> <0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> <1357820178.20090616140700@foucault.co.uk> Message-ID: <4A37C60E.7337.00A0.0@waternet.nl> I think Richard refers to this program: http://www.atmsite.org/contrib/May/mosby/mosby.zip (just found it by Google. This testing method is truly an eye-opener first class for me. Thank you David) Best regards Harro Treur Netherlands >>> Richard in the UK 15:07 Dinsdag 16 Juni 2009 >>> Hello Francis, Tuesday, June 16, 2009, 1:05:17 PM, you wrote: > Who could forget the Mosby null test. Willman Bell is now out of the > patterns. I believe there is a program for printing the pattern for a given mirror. -- Best regards, Richard in the UK _______________________________________________ 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 vorblesnak at peak.org Tue Jun 16 23:24:25 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Tue, 16 Jun 2009 07:24:25 -0700 (PDT) Subject: [ATM] ATM The fused blank is broken Message-ID: <5261.159.121.96.200.1245162265.squirrel@webmail.peak.org> Richard Schwartz reminded me that it is a "FUSED" blank. Put it back in the kiln and fix it! Simple idea. I'll keep the list posted on how that works. David Davis Toledo, OR 97391 >This reminds me of Brashear's tale of the 12" mirror he was working on >broke. He was pretty down about it and when he came home from work, >he saw that his wife cleaned up the shop, got the boiler going, and >the other blank ready to be worked. >Brashear didn't drink, but you can feel his dismay of such an event. >(I would go with Crown Royal myself and use the bag for the secondary >cover as part of the ritual.. hehehehe) >Jason Hissong >http://undermidnight.blogspot.com >http://www.undermidnight.com >http://www.n8xe.com >http://www.jasonhissong.com >(BTW.. I am N8XE, good to see other hams doing atm stuff too!) >On Mon, Jun 15, 2009 at 10:19 AM, Michael Coslo wrote: > I've found that when breaking important glass, (I once dropped and broke an > 8 inch piece of Optical glass that I was going to turn into a nice big > refractor lens) one must make a sacrifice to the Holy Photons. > > 1. Get a bottle of Cuervo Gold > > 2. Pour 2 shot glasses with the tequila > > 3. pour one on the broken mirror or lens > > 4. Partake of the other shot - neat, no ice nor chaser allowed > > 5. Mutter a few words about the first light that never happened > > 6. Repeat as needed. > > note: if desired, you can substitute Makers Mark or Bombay Sapphire - it > just has to be premium stuff. Do not work on your other mirror until the > effects of the sacrifice wear off. > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From nilsolof.carlin at telia.com Tue Jun 16 23:45:36 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Tue, 16 Jun 2009 16:45:36 +0200 Subject: [ATM] ATM: Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> <1357820178.20090616140700@foucault.co.uk> Message-ID: > I believe there is a program for printing the pattern for a given > mirror http://www.atmsite.org/contrib/Holm/invron/invron.html perhaps? Searching on google for "mobsby null test" gives some 180 hits, "mosby null test" 60 or so. "Mobsby" apparently is the correct version. >>>Who remembers Eric Mobsby's brilliant improvement to Ronchi? I don't. (the -74 article was published almost two decades before I developed an interest in optical tests). Clever - yes. Brilliant - I wonder. Is there anyone out there in the wild who actually has used it for figuring, and has had the result confirmed by an independent method? Nils Olof From djd521 at verizon.net Tue Jun 16 23:54:20 2009 From: djd521 at verizon.net (Don D'Egidio) Date: Tue, 16 Jun 2009 10:54:20 -0400 Subject: [ATM] ATM: Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> Message-ID: I do and even bought the one from Willmann-Bell, but soon discovered it works very well for F/7 and slower mirrors. Don ----- Original Message ----- From: To: "ATM list" Sent: Tuesday, June 16, 2009 6:42 AM Subject: [ATM] ATM: Eric Mobsby > Who remembers Eric Mobsby's brilliant improvement to Ronchi? > > I do; guess it just shows how old I am. > D-LZ130 > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From jhissong at gmail.com Tue Jun 16 23:57:42 2009 From: jhissong at gmail.com (Jason Hissong) Date: Tue, 16 Jun 2009 10:57:42 -0400 Subject: [ATM] The fused blank is broken In-Reply-To: <4A36E5E1.6020609@windstream.net> References: <4254.69.59.200.230.1244914992.squirrel@webmail.peak.org> <7ECE7A35-5A58-44C9-B8A9-3F8CB94E6732@psu.edu> <4A36E5E1.6020609@windstream.net> Message-ID: The story was in his autobiography. I don't know if it is published on the web anywhere but I believe you can find the book for sale. It is a good read for mirror makers (and telescope makers too). Jason Hissong On Mon, Jun 15, 2009 at 8:22 PM, waldo kitty wrote: > Jason Hissong wrote: >> >> This reminds me of Brashear's tale of the 12" mirror he was working on >> broke. ?He was pretty down about it and when he came home from work, >> he saw that his wife cleaned up the shop, got the boiler going, and >> the other blank ready to be worked. > > it this story published on the web anywhere? it sounds like it would make > for decent reading ;) > > -- > ? ? ? _\/ > ? ? ?(@@) ? ? ? ? ? ? ? ? ? ? ?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 nilsolof.carlin at telia.com Wed Jun 17 00:01:29 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Tue, 16 Jun 2009 17:01:29 +0200 Subject: [ATM] ATM: Eric Mobsby References: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> Message-ID: > P.S.- As I understand it, the custom grating will give you straight lines > when you have the glass right. And the grating placed just right, in 3 dimensions! Plain old Ronchi is much more forgiving - only one dimension (or at least not quite two). However, if you have the glass right, why do the Mobsby test? If you use the Mobsby test to find out if you *have* the glass right: 1) You think the lines look straight. This can mean a) the test is not sensitive enough to reveal the existing errors of correction b) the figure is indeed right c) there is some under- or overcorrection, but adjusting the longitudinal position made the lines look straight, despite 2) Or you don't think the lines look straight. d) the correction actually isn't quite right e) the grid isn't placed close enough to its intended position there may be other possibilities. But if this, or any null test, shows no deviation from perfect, the likely conclusion is that the test isn't sensitive enough to be useful. Nils Olof From scopebuilder at gmail.com Wed Jun 17 00:26:24 2009 From: scopebuilder at gmail.com (Scope Builder) Date: Tue, 16 Jun 2009 11:26:24 -0400 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> Message-ID: Hi, All. I'll open up the can of worms here... What's the general concensus of the better method: Mobsby's use of the Ronchi or the Ross Null? Dave From gfbrandenburg at yahoo.com Wed Jun 17 00:40:23 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Tue, 16 Jun 2009 08:40:23 -0700 (PDT) Subject: [ATM] ATM: Eric Mobsby Message-ID: <309076.69196.qm@web111507.mail.gq1.yahoo.com> I tried it, ordering the gratings from WillBell, but without success. Way way too difficult to use. 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, 6/16/09, Nils Olof Carlin wrote: > From: Nils Olof Carlin > Subject: Re: [ATM] ATM: Eric Mobsby > To: stainless_steel at suddenlink.net, "ATM list" > Date: Tuesday, June 16, 2009, 11:01 AM > > > P.S.- As I understand it, the custom grating will give > you straight lines > > when you have the glass right. > > And the grating placed just right, in 3 dimensions! Plain > old Ronchi is much more forgiving - only one dimension (or > at least not quite two). However, if you have the glass > right, why do the Mobsby test? > > If you use the Mobsby test to find out if you *have* the > glass right: > 1) You think the lines look straight. This can mean > a) the test is not sensitive enough to reveal the existing > errors of correction > b) the figure is indeed right > c) there is some under- or overcorrection, but adjusting > the longitudinal position made the lines look straight, > despite > 2) Or you don't think the lines look straight. > d) the correction actually isn't quite right > e) the grid isn't placed close enough to its intended > position > there may be other possibilities. But if this, or any null > test, shows no deviation from perfect, the likely conclusion > is that the test isn't sensitive enough to be useful. > > Nils Olof > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From vladimir.galogaza1 at zg.t-com.hr Wed Jun 17 01:35:08 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Tue, 16 Jun 2009 18:35:08 +0200 Subject: [ATM] ATM: Eric Mobsby, should be Karl Ludwig Bath References: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> Message-ID: Watching Ronchi thread I think that it is just about right time to quote Mel. "Time to take a BATH !" (Mel Bartels) Regards Vladimir. From drewclan at aol.com Wed Jun 17 01:32:27 2009 From: drewclan at aol.com (drewclan at aol.com) Date: Tue, 16 Jun 2009 12:32:27 -0400 Subject: [ATM] Mosby and Ross Null comparo Message-ID: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> Oh, Dave, that is a can of worms! The way I see it: Mosby is an interesting test where?a different grating is needed for each individual focal length. So you have to polish out and then carefully measure your fl before making or buying a grating. Ross null on the other hand, can be used for an almost infinite number of different mirrors. And of course it is used with the knife edge as much as the ronchi. Jay in CT From nilsolof.carlin at telia.com Wed Jun 17 01:42:10 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Tue, 16 Jun 2009 18:42:10 +0200 Subject: [ATM] ATM: Eric Mobsby, should be Karl Ludwig Bath References: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> Message-ID: > "Time to take a BATH !" Seems someone is hitting the wrong key, and mobs by interfering with this thread... From peter.w at wangsnessoptics.com Wed Jun 17 01:45:47 2009 From: peter.w at wangsnessoptics.com (Peter Wangsness) Date: Tue, 16 Jun 2009 09:45:47 -0700 Subject: [ATM] Broken fusion blank Message-ID: Hi, If it is any consolation, my personal best of blank breaking was a $40,000 blank with the last sheet of 40? wide Pyrex ever made by Corning. Someone else broke the rest of the crate. I know of others that have wiped out $1,000,000+ blanks, so you can still, keep your amateur status. Best wishes, Peter Wangsness Wangsness Optics We can now accept credit cards. From vladimir.galogaza1 at zg.t-com.hr Wed Jun 17 02:21:29 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Tue, 16 Jun 2009 19:21:29 +0200 Subject: [ATM] ATM: Eric Mobsby, should be Karl Ludwig Bath References: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> Message-ID: <9C6468BF5CD34024A64232DE466B321C@piv555a133b59e> > > "Time to take a BATH !" >Seems someone is hitting the wrong key, and mobs by interfering with this >thread... By no means. It was right key and right suggestion. Regards Vladimir. From jroyston at gmx.de Wed Jun 17 02:13:08 2009 From: jroyston at gmx.de (Jeremy Royston) Date: Tue, 16 Jun 2009 19:13:08 +0200 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> Message-ID: <002901c9eea5$b8babc70$2a303550$@de> Hello Dave, It's a bit like comparing apples and pears. Mobsby is not quantitative, and it doesn't show the even the sign of the error intuitively. The advantage is that it's easy. The Ross null test needs a lens which is just as exact as the accuracy which you need, but it does show the error well. The Foucault test is accurate, if you have some experience, there are plenty of programs for evaluating the results, and they show the error. It does not, however, show astigmatism unless it's fairly bad. I always plug the 2D Hartmann test. It's quick, accurate, and gives you a good idea of the figure near the centre and edges, as well as showing even very small astigmatism Best wishes, Jerry -----Urspr?ngliche Nachricht----- Von: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] Im Auftrag von Scope Builder Gesendet: 16 June 2009 17:26 An: atm at atmlist.net Betreff: Re: [ATM] ATM: Eric Mobsby Hi, All. I'll open up the can of worms here... What's the general concensus of the better method: Mobsby's use of the Ronchi or the Ross Null? Dave _______________________________________________ ATM mailing list http://www.atmlist.net/ From shane at ct-astronomer.com Wed Jun 17 03:50:06 2009 From: shane at ct-astronomer.com (Shane LaPierre) Date: Tue, 16 Jun 2009 14:50:06 -0400 Subject: [ATM] Calculating alt/az question Message-ID: <8298B763-B37E-4B74-AF4A-43FE16C28E6E@ct-astronomer.com> I am writing some SW to calculate the altitude of an object above the observer's horizon. I have been using this website to check the output and am a little unclear on the math: http://www.stargazing.net/kepler/altaz.html // the basic formula sin(ALT) = sin(DEC)*sin(LAT)+cos(DEC)*cos(LAT)*cos(HA) // the formula with my results sin(ALT) = 0.5943550 * 0.7933533 + 0.8042028 * 0.6087614 * 0.5823696 = 0.4715335 + 0.2851093 = 0.7566428 // formatted output - I assume this is a conversion of results from above (0.7566428) to altitude in degrees ALT = 49.169122 degrees I have arrived at the value 0.7566428.... but how to convert that to ALT in degrees is my problem. Any ideas? Thanks, Shane From stainless_steel at suddenlink.net Wed Jun 17 03:51:54 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 13:51:54 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: References: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> Message-ID: Foucault will not lie to you. You can misinterpret it, but it is idiot proof. http://www.atmsite.org/contrib/Harbour/Foucault.html In defense of the mobsby test, it is very elegant. I would use it, if I hadn't already fallen in love with Foucault. My readers lovedc Foucault so much, that on my page for "borrowing" my #5 tester, about the fifth person who borrowed it never returned it. I expected that, or I wouldn't have loaned it out. My mirror making days are over, partly due to Rheumatoid Arthritis, and partly do to Sciatica, and other unspecified aches and pains. (Orthopedic type injuries, pretty bad). Yes, you are right. That's why I used Foucault (when I made mirrors, or fixed them) D-LZ130 ----- Original Message ----- From: "Nils Olof Carlin" To: ; "ATM list" Sent: Tuesday, June 16, 2009 10:01 AM Subject: Re: [ATM] ATM: Eric Mobsby > >> P.S.- As I understand it, the custom grating will give you straight lines >> when you have the glass right. > > And the grating placed just right, in 3 dimensions! Plain old Ronchi is > much > more forgiving - only one dimension (or at least not quite two). However, > if > you have the glass right, why do the Mobsby test? > > If you use the Mobsby test to find out if you *have* the glass right: > 1) You think the lines look straight. This can mean > a) the test is not sensitive enough to reveal the existing errors of > correction > b) the figure is indeed right > c) there is some under- or overcorrection, but adjusting the longitudinal > position made the lines look straight, despite > 2) Or you don't think the lines look straight. > d) the correction actually isn't quite right > e) the grid isn't placed close enough to its intended position > there may be other possibilities. But if this, or any null test, shows no > deviation from perfect, the likely conclusion is that the test isn't > sensitive enough to be useful. > > Nils Olof > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From daze39 at earthlink.net Wed Jun 17 03:51:26 2009 From: daze39 at earthlink.net (David Weinshenker) Date: Tue, 16 Jun 2009 11:51:26 -0700 Subject: [ATM] Calculating alt/az question In-Reply-To: <8298B763-B37E-4B74-AF4A-43FE16C28E6E@ct-astronomer.com> References: <8298B763-B37E-4B74-AF4A-43FE16C28E6E@ct-astronomer.com> Message-ID: <4A37E9AE.7070705@earthlink.net> Shane LaPierre wrote: > I am writing some SW to calculate the altitude of an object above the > observer's horizon. I have been using this website to check the output > and am a little unclear on the math: > http://www.stargazing.net/kepler/altaz.html > > // the basic formula > sin(ALT) = sin(DEC)*sin(LAT)+cos(DEC)*cos(LAT)*cos(HA) > // the formula with my results > sin(ALT) = 0.5943550 * 0.7933533 + 0.8042028 * 0.6087614 * 0.5823696 > = 0.4715335 + 0.2851093 > = 0.7566428 > > // formatted output - I assume this is a conversion of results from > above (0.7566428) to altitude in degrees > ALT = 49.169122 degrees > > I have arrived at the value 0.7566428.... but how to convert that to ALT > in degrees is my problem. Any ideas? The value calculated in that formula is sin(ALT) - the numerical value of the sine of the angle. To get the angle in degrees, you need to take the inverse sine (also known as arcsine or asin) of that value. The calculator utility on my PC does in fact confirm that asin(0.7566428) = 49.169122 degrees. -dave w From stainless_steel at suddenlink.net Wed Jun 17 04:00:28 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 14:00:28 -0500 Subject: [ATM] Fw: ATM: Eric Mobsby Message-ID: ----- Original Message ----- From: To: "Nils Olof Carlin" ; "ATM list" Sent: Tuesday, June 16, 2009 1:51 PM Subject: Re: [ATM] ATM: Eric Mobsby > > Foucault will not lie to you. You can misinterpret it, but it is idiot > proof. > > http://www.atmsite.org/contrib/Harbour/Foucault.html > > In defense of the mobsby test, it is very elegant. I would use it, if I > hadn't already fallen in love with Foucault. My readers lovedc Foucault so > much, that on my page for "borrowing" my #5 tester, about the fifth person > who borrowed it never returned it. I expected that, or I wouldn't have > loaned it out. > > My mirror making days are over, partly due to Rheumatoid Arthritis, and > partly do to Sciatica, and other unspecified aches and pains. (Orthopedic > type injuries, pretty bad). > > Yes, you are right. That's why I used Foucault (when I made mirrors, or > fixed them) > > > D-LZ130 > P.S.- http://www.atmsite.org/contrib/Harbour/Tester.html > > ----- Original Message ----- > From: "Nils Olof Carlin" > To: ; "ATM list" > Sent: Tuesday, June 16, 2009 10:01 AM > Subject: Re: [ATM] ATM: Eric Mobsby > > >> >>> P.S.- As I understand it, the custom grating will give you straight >>> lines >>> when you have the glass right. >> >> And the grating placed just right, in 3 dimensions! Plain old Ronchi is >> much >> more forgiving - only one dimension (or at least not quite two). However, >> if >> you have the glass right, why do the Mobsby test? >> >> If you use the Mobsby test to find out if you *have* the glass right: >> 1) You think the lines look straight. This can mean >> a) the test is not sensitive enough to reveal the existing errors of >> correction >> b) the figure is indeed right >> c) there is some under- or overcorrection, but adjusting the longitudinal >> position made the lines look straight, despite >> 2) Or you don't think the lines look straight. >> d) the correction actually isn't quite right >> e) the grid isn't placed close enough to its intended position >> there may be other possibilities. But if this, or any null test, shows no >> deviation from perfect, the likely conclusion is that the test isn't >> sensitive enough to be useful. >> >> Nils Olof >> > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 > 07:41:00 > From stainless_steel at suddenlink.net Wed Jun 17 04:01:35 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 14:01:35 -0500 Subject: [ATM] ATM: Eric Mobsby, should be Karl Ludwig Bath In-Reply-To: References: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> Message-ID: <2F0ABD4E2D614032BF26CD02C3F40094@R101> Roger, Wilco. D-LZ130 ----- Original Message ----- From: "Vladimir Galogaza" To: "ATM List" Sent: Tuesday, June 16, 2009 11:35 AM Subject: Re: [ATM] ATM: Eric Mobsby, should be Karl Ludwig Bath > Watching Ronchi thread I think that it is just about right time to > quote Mel. > > "Time to take a BATH !" > (Mel Bartels) > > Regards > Vladimir. > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From shane at ct-astronomer.com Wed Jun 17 04:04:32 2009 From: shane at ct-astronomer.com (Shane LaPierre) Date: Tue, 16 Jun 2009 15:04:32 -0400 Subject: [ATM] Calculating alt/az question In-Reply-To: <5095c3a00906161200t15fb2246w2a8f2bf44679c440@mail.gmail.com> References: <8298B763-B37E-4B74-AF4A-43FE16C28E6E@ct-astronomer.com> <5095c3a00906161200t15fb2246w2a8f2bf44679c440@mail.gmail.com> Message-ID: Chuck, That was it. It is C language... I'm really a sw developer for business apps, so I don't get into heavy mathematics often. Anyway, I appreciate the tip. The response was in radians, when I converted to degrees. Thanks again, Shane On Jun 16, 2009, at 3:00 PM, Chuck Hartley wrote: > Shane, > > sin(ALT) = 0.7566428 so just take the inverse sine of that number > to get degrees (or more likely radians). You didn't say what > language you are using so I'll assume its C, but the asin() function > returns radians. > > Chuck > > On Tue, Jun 16, 2009 at 2:50 PM, Shane LaPierre > wrote: > I am writing some SW to calculate the altitude of an object above > the observer's horizon. I have been using this website to check the > output and am a little unclear on the math: > http://www.stargazing.net/kepler/altaz.html > > // the basic formula > sin(ALT) = sin(DEC)*sin(LAT)+cos(DEC)*cos(LAT)*cos(HA) > // the formula with my results > sin(ALT) = 0.5943550 * 0.7933533 + 0.8042028 * 0.6087614 * 0.5823696 > = 0.4715335 + 0.2851093 > = 0.7566428 > > // formatted output - I assume this is a conversion of results from > above (0.7566428) to altitude in degrees > ALT = 49.169122 degrees > > I have arrived at the value 0.7566428.... but how to convert that to > ALT in degrees is my problem. Any ideas? > > Thanks, > Shane > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From stainless_steel at suddenlink.net Wed Jun 17 04:05:49 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 14:05:49 -0500 Subject: [ATM] Mosby and Ross Null comparo In-Reply-To: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> Message-ID: <1D11C9A894B348F9BA87F91996B7F7EA@R101> Read the introduction to my article: http://www.atmsite.org/contrib/Harbour/Foucault.html "Dave" Ross was essentially what they used (with little bitty mirrors) to wreck the 92" Hubble primary. I rest my case for Foucault. D-LZ130 ----- Original Message ----- From: To: Sent: Tuesday, June 16, 2009 11:32 AM Subject: [ATM] Mosby and Ross Null comparo > Oh, Dave, that is a can of worms! The way I see it: > > Mosby is an interesting test where?a different grating is needed for each > individual focal length. So you have to polish out and then carefully > measure your fl before making or buying a grating. > > Ross null on the other hand, can be used for an almost infinite number of > different mirrors. And of course it is used with the knife edge as much as > the ronchi. > > Jay in CT > > _______________________________________________ > 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: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From stainless_steel at suddenlink.net Wed Jun 17 04:11:45 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 14:11:45 -0500 Subject: [ATM] ATM: Eric Mobsby, should be Karl Ludwig Bath In-Reply-To: <9C6468BF5CD34024A64232DE466B321C@piv555a133b59e> References: <97D8C7B8A4CF4E69A29D825C7AE67136@R101> <9C6468BF5CD34024A64232DE466B321C@piv555a133b59e> Message-ID: <782C48B0BDA24D9AB82F96CD92E2EC97@R101> Foucault. ----- Original Message ----- From: "Vladimir Galogaza" To: "Nils Olof Carlin" Cc: "ATM List" Sent: Tuesday, June 16, 2009 12:21 PM Subject: Re: [ATM] ATM: Eric Mobsby, should be Karl Ludwig Bath > > >> "Time to take a BATH !" > >>Seems someone is hitting the wrong key, and mobs by interfering with this >>thread... > > By no means. It was right key and right suggestion. > > Regards > Vladimir. > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From stainless_steel at suddenlink.net Wed Jun 17 04:15:16 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 14:15:16 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <002901c9eea5$b8babc70$2a303550$@de> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> <002901c9eea5$b8babc70$2a303550$@de> Message-ID: Hartmann is excellent, and underappreciated. It was used to figure the five meter Hale mirror. Did any of you know that? Please check in, and let me know who knew that. D-LZ130 Astigmatism is inexcusable; I never got it, no one ever should. D-LZ130 ----- Original Message ----- From: "Jeremy Royston" To: "'Scope Builder'" Cc: Sent: Tuesday, June 16, 2009 12:13 PM Subject: Re: [ATM] ATM: Eric Mobsby Hello Dave, It's a bit like comparing apples and pears. Mobsby is not quantitative, and it doesn't show the even the sign of the error intuitively. The advantage is that it's easy. The Ross null test needs a lens which is just as exact as the accuracy which you need, but it does show the error well. The Foucault test is accurate, if you have some experience, there are plenty of programs for evaluating the results, and they show the error. It does not, however, show astigmatism unless it's fairly bad. I always plug the 2D Hartmann test. It's quick, accurate, and gives you a good idea of the figure near the centre and edges, as well as showing even very small astigmatism Best wishes, Jerry -----Urspr?ngliche Nachricht----- Von: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] Im Auftrag von Scope Builder Gesendet: 16 June 2009 17:26 An: atm at atmlist.net Betreff: Re: [ATM] ATM: Eric Mobsby Hi, All. I'll open up the can of worms here... What's the general concensus of the better method: Mobsby's use of the Ronchi or the Ross Null? Dave _______________________________________________ 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: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From arjan.te.marvelde at hetnet.nl Wed Jun 17 04:34:37 2009 From: arjan.te.marvelde at hetnet.nl (Arjan te Marvelde (hetnet)) Date: Tue, 16 Jun 2009 21:34:37 +0200 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: References: Message-ID: <4A37F3CD.1060607@hetnet.nl> Martin Trittelvitz has: http://www.marty-atm.de/mosby.htm >>> Is there anyone out there in the wild who actually has used it for figuring, and has had the result confirmed by an independent method? From mbartels at bbastrodesigns.com Wed Jun 17 04:35:29 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Tue, 16 Jun 2009 13:35:29 -0600 Subject: [ATM] Ronchi Grating Question In-Reply-To: <2015F9C887DC45F39DABF13D249AE59A@dittda7685d135> References: <000f01c9ec78$3a205d40$a9fe1345@amd> <7F87286500D843538529A4E8A9ED6A6C@dittda7685d135> <2015F9C887DC45F39DABF13D249AE59A@dittda7685d135> Message-ID: <20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com> >>> "pattern-matching" by eye is bound to fail Bound to fail? Gosh, my 13" f/3.0 was figured by pattern matching (as have been many dozens of mirrors of mine and my students over the years). So maybe better to say that it "can fail"? Mel Bartels Quoting Nils Olof Carlin : > Richard, > > yes, but why bother? A Ronchi grid may be helpful for detecting zones > or roughness (including a turned edge), but sweeping a Foucault > knife-edge across the field will give the same information (and with no > diffraction grating side-effects). But it is of doubtful value for > figuring. With diligence, you *can* extract zonal information by > measuring the positions of the bands, and process it with SIXTESTS, but > who does? It may show when you have polished to a decent sphere, but > "pattern-matching" by eye is bound to fail (for an explanation, see > Suiter's Star Testing...). From mbartels at bbastrodesigns.com Wed Jun 17 04:36:34 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Tue, 16 Jun 2009 13:36:34 -0600 Subject: [ATM] Betr.: Re: ATM: Eric Mobsby In-Reply-To: <4A37C60E.7337.00A0.0@waternet.nl> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101> <0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> <1357820178.20090616140700@foucault.co.uk> <4A37C60E.7337.00A0.0@waternet.nl> Message-ID: <20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> Careful, the test as explained in the original article had limitations with respect to aperture and speed. Mel Bartels Quoting Harro Treur : > I think Richard refers to this program: > http://www.atmsite.org/contrib/May/mosby/mosby.zip > (just found it by Google. This testing method is truly an eye-opener > first class for me. Thank you David) > > Best regards > Harro Treur > Netherlands > > >>>> Richard in the UK 15:07 Dinsdag 16 Juni 2009 >>> > Hello Francis, > > Tuesday, June 16, 2009, 1:05:17 PM, you wrote: > >> Who could forget the Mosby null test. Willman Bell is now out of the >> patterns. > > I believe there is a program for printing the pattern for a given > mirror. > > -- > Best regards, > Richard in the UK > > _______________________________________________ > 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. > *********************************************************************************************** > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mbartels at bbastrodesigns.com Wed Jun 17 04:39:41 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Tue, 16 Jun 2009 13:39:41 -0600 Subject: [ATM] Broken fusion blank In-Reply-To: References: Message-ID: <20090616133941.1k07ufxpssgcscwk@mail.bbastrodesigns.com> I saw a million dollar broken secondary at the Mirror Lab... Mel Bartels Quoting Peter Wangsness : > > Hi, > > If it is any consolation, my personal best of blank breaking was a $40,000 > blank with the last sheet of 40? wide Pyrex ever made by Corning. Someone > else broke the rest of the crate. I know of others that have wiped out > $1,000,000+ blanks, so you can still, keep your amateur status. > > > Best wishes, > > Peter Wangsness > > Wangsness Optics > > We can now accept credit cards. > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From rmay at nethere.com Wed Jun 17 05:13:47 2009 From: rmay at nethere.com (Bob May) Date: Tue, 16 Jun 2009 13:13:47 -0700 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135> <20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com> Message-ID: <000601c9eebe$f581ef20$5d9a5545@amd> When you get the experience with gratings, you can indeed do a fair job of getting the right shape. However, it is a subjective test in that regard and I wouldn't guarantee that you really have the "right" shape anywhere near as it could be determined by a Foucault test. The truth is that the Foucault test does have a problem with determining the smoothness of the surface (go see Dave Harbour's article on the Foucault test for what it can be) so BOTH tests are really needed to see what the true shape of the surface is. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From blaktony86 at yahoo.com Wed Jun 17 05:17:38 2009 From: blaktony86 at yahoo.com (TONY BLAKESLEY) Date: Tue, 16 Jun 2009 13:17:38 -0700 (PDT) Subject: [ATM] webcam 2d hartmann test and foucault image analyzer Message-ID: <399241.27162.qm@web81906.mail.mud.yahoo.com> Hello, ? I did a search through the atmlist on the 2d hartmann test using a webcam. The test seems accurate. Is the test hard to setup? Other than making a "checkboard" mask, what is so difficult about it? Does the test need precise measurment of various focal points? Anyone have personal experience with this? Just place mask, shoot some images, and let the computer analyze? ? Also I read about a program called the foucault image analyzer. It takes images at precise distances and analyzes the images. Anyone have experience with this program as well? ? I?am highly interested in these programs?as the computer does the analyzing. I have experience with the Ronchi and some experience with the foucault test but it would be nice to get something that is highly accurate, can produce numbers, and is consistent in results. ? So far the Ronchi test has given me a pretty instantaneous reading of my mirrors surface and I enjoy that aspect of the test, but then again it would be nice to get some numbers on my mirror. ? Maybe someone can devise a Ronchi test image analyzer! ? -Tony ? ? From rmay at nethere.com Wed Jun 17 05:23:20 2009 From: rmay at nethere.com (Bob May) Date: Tue, 16 Jun 2009 13:23:20 -0700 Subject: [ATM] Mosby and Ross Null comparo References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> Message-ID: <003b01c9eec0$4b5baac0$5d9a5545@amd> >From qhat I've heard on the Hubble mirror, that was an Offner Null test that gave the wrong answer to the shape. The null mirrors were spaced wrong as the mirror was different from the military mirrors that the company was also making at the time and the tester was borrowed from the military side and respaced for the Hubble. Unfortunately, the tech doing the reassambly did the job wrong. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From stainless_steel at suddenlink.net Wed Jun 17 05:32:20 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 15:32:20 -0500 Subject: [ATM] Mosby and Ross Null comparo In-Reply-To: <8CBBCD1F122170E-19C-1F59@FWM-D06.sysops.aol.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <8CBBCD1F122170E-19C-1F59@FWM-D06.sysops.aol.com> Message-ID: <74D5CDC6F889466498852C6B0CAAB6D1@R101> What can I say? It was a modification of the null test at center of curvature that was used. A lens was out of position by a tiny bit. No lenses or mirrors in a Foucault tester. D-LZ130 ----- Original Message ----- From: drewclan at aol.com To: stainless_steel at suddenlink.net Sent: Tuesday, June 16, 2009 2:44 PM Subject: Re: [ATM] Mosby and Ross Null comparo Hey, great to hear from you Davie! Poor Ross null test, after Hubble it will never get a good rap. Jay -----Original Message----- From: stainless_steel at suddenlink.net To: atm at atmlist.net; drewclan at aol.com Sent: Tue, Jun 16, 2009 3:05 pm Subject: Re: [ATM] Mosby and Ross Null comparo Read the introduction to my article: http://www.atmsite.org/contrib/Harbour/Foucault.html "Dave" Ross was essentially what they used (with little bitty mirrors) to wreck the 92" Hubble primary. I rest my case for Foucault. D-LZ130 ----- Original Message ----- From: To: Sent: Tuesday, June 16, 2009 11:32 AM Subject: [ATM] Mosby and Ross Null comparo > Oh, Dave, that is a can of worms! The way I see it: > > Mosby is an interesting test where?a different grating is needed for each > > individual focal length. So you have to polish out and then carefully > > measure your fl before making or buying a grating. > > Ross null on the other hand, can be used for an almost infinite number of > > different mirrors. And of course it is used with the knife edge as much > as > the ronchi. > > Jay in CT > > _______________________________________________ > 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: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 Make your summer sizzle with fast and easy recipes for the grill. No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From stainless_steel at suddenlink.net Wed Jun 17 05:33:41 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Tue, 16 Jun 2009 15:33:41 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> <002901c9eea5$b8babc70$2a303550$@de> Message-ID: I am not a champion of Ross null test. D-LZ130 ----- Original Message ----- From: To: ; "'Scope Builder'" Cc: Sent: Tuesday, June 16, 2009 2:15 PM Subject: Re: [ATM] ATM: Eric Mobsby Hartmann is excellent, and underappreciated. It was used to figure the five meter Hale mirror. Did any of you know that? Please check in, and let me know who knew that. D-LZ130 Astigmatism is inexcusable; I never got it, no one ever should. D-LZ130 ----- Original Message ----- From: "Jeremy Royston" To: "'Scope Builder'" Cc: Sent: Tuesday, June 16, 2009 12:13 PM Subject: Re: [ATM] ATM: Eric Mobsby Hello Dave, It's a bit like comparing apples and pears. Mobsby is not quantitative, and it doesn't show the even the sign of the error intuitively. The advantage is that it's easy. The Ross null test needs a lens which is just as exact as the accuracy which you need, but it does show the error well. The Foucault test is accurate, if you have some experience, there are plenty of programs for evaluating the results, and they show the error. It does not, however, show astigmatism unless it's fairly bad. I always plug the 2D Hartmann test. It's quick, accurate, and gives you a good idea of the figure near the centre and edges, as well as showing even very small astigmatism Best wishes, Jerry -----Urspr?ngliche Nachricht----- Von: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] Im Auftrag von Scope Builder Gesendet: 16 June 2009 17:26 An: atm at atmlist.net Betreff: Re: [ATM] ATM: Eric Mobsby Hi, All. I'll open up the can of worms here... What's the general concensus of the better method: Mobsby's use of the Ronchi or the Ross Null? Dave _______________________________________________ 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: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 _______________________________________________ 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: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From nilsolof.carlin at telia.com Wed Jun 17 05:48:41 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Tue, 16 Jun 2009 22:48:41 +0200 Subject: [ATM] Betr.: Re: ATM: Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl> <20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> Message-ID: Mel, >>>> "pattern-matching" by eye is bound to fail > > Bound to fail? Gosh, my 13" f/3.0 was figured by pattern matching (as > have been many dozens of mirrors of mine and my students over the years). > So maybe better to say that it "can fail"? Could we say "may succeed"? What, if anything, did a Foucault test say? Using a plain Ronchi grid, one thing one can do is calculate (Jim Burrows' DIFFRACT should work, but so may other software) the relative positions of the bands across the mirror face, and mark the centers on a pinstick (Everest style) for 5 (or 7) bands. Then when testing, move the stage until the outer pair of bands match their pins. Then, do the inner bands match theirs, too? If not, figuring isn't right yet. Assuming the grid is inside the ROC (barrel-shaped bands) - if the inner bands are inside their pins, it means undercorrection. (I hope I got that right!) The bending of the bands will tell nothing more than that about the correction. This would be roughly equivalent to a 2 (or 3) zone Foucault test. Nils Olof >From a children's book: What bird always succeeds? A toothless budgie From nilsolof.carlin at telia.com Wed Jun 17 05:49:33 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Tue, 16 Jun 2009 22:49:33 +0200 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com> <000601c9eebe$f581ef20$5d9a5545@amd> Message-ID: > ... The truth is that the Foucault test does have a > problem with determining the smoothness of the surface (go see > Dave Harbour's article on the Foucault test for what it can be) > so BOTH tests are really needed to see what the true shape of the > surface is. Placing the KE a bit outside (or inside) the paraxial ROC and scanning it side to side can reveal those things reasonably well, I trust. Nils Olof From lowe at nanotechsys.com Wed Jun 17 05:55:18 2009 From: lowe at nanotechsys.com (Jeff Lowe) Date: Tue, 16 Jun 2009 16:55:18 -0400 Subject: [ATM] Broken fusion blank In-Reply-To: References: Message-ID: <4A3806B6.6000809@nanotechsys.com> Mel Bartels Wrote: > I saw a million dollar broken secondary at the Mirror Lab... I remember the day the Alvan Clark flat broke in half at Stellafane. Anything else is just money...... Jeff Lowe From s.c.koehler at gmail.com Wed Jun 17 06:06:33 2009 From: s.c.koehler at gmail.com (Stephen Koehler) Date: Tue, 16 Jun 2009 16:06:33 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <399241.27162.qm@web81906.mail.mud.yahoo.com> References: <399241.27162.qm@web81906.mail.mud.yahoo.com> Message-ID: <8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> Tony, Maybe someone can devise a Ronchi test image analyzer! > Regarding computer-assisted analysis techniques, the following are the ones I have heard of. Each has its advantages and disadvantages. 1. Computer null finding of static Foucault images + simple, uses standard foucault setup - resolution similar to standard Foucault - only across one diameter, so it can miss astigmatism 2. Automated Foucault + much higher resolution than (1) - still only across one diameter - need to build accurate, automated platform movement 3. 2D Hartmann + fairly simple equipment + reads whole mirror surface - still need accurate state positioning (like Foucault) - fairly low resolution - cutting the mask is tedious, and only works for one size of mirror 4. Bath interferometer + high resolution over the entire surface + no need for a stage that measures position - a bit more complex equipment than the others, but not all that bad - needs a stage that moves in x, y, and z. I'm not sure a Ronchi image analyzer would give you any benefits not already seen in these other methods. If you're interested in doing something more that Foucault, I would highly recommend looking at the Bath interferometer. The optical parts can be put together for about $50. You do need a suitable camera (digital SLR or modified webcam). There are two free analysis programs you can use to process the images. There's a lot of information on the interferometer Wiki, and on the Yahoo interferometry group. http://starryridge.com/mediawiki-1.9.1/index.php?title=Main_Page -- Steve Koehler From mbartels at bbastrodesigns.com Wed Jun 17 06:15:23 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Tue, 16 Jun 2009 15:15:23 -0600 Subject: [ATM] Ronchi Grating Question In-Reply-To: <000601c9eebe$f581ef20$5d9a5545@amd> References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135> <20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com> <000601c9eebe$f581ef20$5d9a5545@amd> Message-ID: <20090616151523.6svbzpde2scsw8oo@mail.bbastrodesigns.com> > When you get the experience with gratings, you can indeed do a > fair job of getting the right shape. However, it is a subjective > test in that regard and I wouldn't guarantee that you really have > the "right" shape anywhere near as it could be determined by a > Foucault test Tell me, what makes an excellent optic, a good optic, a poor optic? You cannot escape entering the subjective realm when describing visual experiences. The idea that Foucault can determine the "right" shape is logically impossible. The Bath interferometer (and similar) gets right to a comprehensive Strehl/RMS, so with high probability can be mapped to subjective experiences. As long as mirror testing is seen as an engineering issue and not a human problem, the community will struggle with mysterious maladies and mysteries. Mel Bartels From mbartels at bbastrodesigns.com Wed Jun 17 06:19:34 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Tue, 16 Jun 2009 15:19:34 -0600 Subject: [ATM] Betr.: Re: ATM: Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl> <20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> Message-ID: <20090616151934.29sfybj14w8o0g0g@mail.bbastrodesigns.com> That's not how I do the pattern matching Ronchi test. Get away from the 'measuring' aspect and concentrate more on the qualitative comparison. The human eye-brain is remarkably sensitive. Just because it can't be measured doesn't mean that it's somehow inferior or invalid or to be judged harshly. Mel Bartels Quoting Nils Olof Carlin : > Mel, > > >>>>> "pattern-matching" by eye is bound to fail >> >> Bound to fail? Gosh, my 13" f/3.0 was figured by pattern matching (as >> have been many dozens of mirrors of mine and my students over the years). >> So maybe better to say that it "can fail"? > > Could we say "may succeed"? What, if anything, did a Foucault test say? > > Using a plain Ronchi grid, one thing one can do is calculate (Jim Burrows' > DIFFRACT should work, but so may other software) the relative positions of > the bands across the mirror face, and mark the centers on a pinstick > (Everest style) for 5 (or 7) bands. > Then when testing, move the stage until the outer pair of bands match their > pins. Then, do the inner bands match theirs, too? If not, figuring isn't > right yet. Assuming the grid is inside the ROC (barrel-shaped bands) - if > the inner bands are inside their pins, it means undercorrection. (I hope I > got that right!) The bending of the bands will tell nothing more than that > about the correction. > This would be roughly equivalent to a 2 (or 3) zone Foucault test. > > Nils Olof > > > > >> From a children's book: What bird always succeeds? > > > > > > A toothless budgie > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Wed Jun 17 06:22:23 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Tue, 16 Jun 2009 15:22:23 -0600 Subject: [ATM] Ronchi Grating Question In-Reply-To: References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com> <000601c9eebe$f581ef20$5d9a5545@amd> Message-ID: <20090616152223.8d32f4jv488scw8k@mail.bbastrodesigns.com> Ah, so you do admit to subjective qualitative judgements . Don't fail to recognize the success I have with mirror classes using the Ronchi test. Mel Bartels Quoting Nils Olof Carlin : > > >> ... The truth is that the Foucault test does have a >> problem with determining the smoothness of the surface (go see >> Dave Harbour's article on the Foucault test for what it can be) >> so BOTH tests are really needed to see what the true shape of the >> surface is. > > Placing the KE a bit outside (or inside) the paraxial ROC and scanning > it side to side can reveal those things reasonably well, I trust. > > Nils Olof > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Wed Jun 17 06:24:37 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Tue, 16 Jun 2009 15:24:37 -0600 Subject: [ATM] Mosby and Ross Null comparo In-Reply-To: <74D5CDC6F889466498852C6B0CAAB6D1@R101> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <8CBBCD1F122170E-19C-1F59@FWM-D06.sysops.aol.com> <74D5CDC6F889466498852C6B0CAAB6D1@R101> Message-ID: <20090616152437.rdwcha4mskw4sw8o@mail.bbastrodesigns.com> > It was a modification of the null test at center of curvature that was > used. A lens was out of position by a tiny bit. No lenses or mirrors in > a Foucault tester. And why was the lens out of position? That's a deeper reason for the Hubble failure. Ask the 5 whys to get to the true root cause. Mel Bartels From jroyston at gmx.de Wed Jun 17 06:31:10 2009 From: jroyston at gmx.de (Jeremy Royston) Date: Tue, 16 Jun 2009 23:31:10 +0200 Subject: [ATM] Calculating alt/az question In-Reply-To: <8298B763-B37E-4B74-AF4A-43FE16C28E6E@ct-astronomer.com> References: <8298B763-B37E-4B74-AF4A-43FE16C28E6E@ct-astronomer.com> Message-ID: <002d01c9eec9$c4d4d710$4e7e8530$@de> Hello Shane, The answer is ALT=arcsin(0.7566428), a description of the function is in the Excel help. Some programs deliver the answer in radians, not degrees Jerry -----Urspr?ngliche Nachricht----- Von: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] Im Auftrag von Shane LaPierre Gesendet: 16 June 2009 20:50 An: ATM list Betreff: [ATM] Calculating alt/az question I am writing some SW to calculate the altitude of an object above the observer's horizon. I have been using this website to check the output and am a little unclear on the math: http://www.stargazing.net/kepler/altaz.html // the basic formula sin(ALT) = sin(DEC)*sin(LAT)+cos(DEC)*cos(LAT)*cos(HA) // the formula with my results sin(ALT) = 0.5943550 * 0.7933533 + 0.8042028 * 0.6087614 * 0.5823696 = 0.4715335 + 0.2851093 = 0.7566428 // formatted output - I assume this is a conversion of results from above (0.7566428) to altitude in degrees ALT = 49.169122 degrees I have arrived at the value 0.7566428.... but how to convert that to ALT in degrees is my problem. Any ideas? Thanks, Shane _______________________________________________ ATM mailing list http://www.atmlist.net/ From holmmarkd at gmail.com Wed Jun 17 07:48:01 2009 From: holmmarkd at gmail.com (Mark Holm) Date: Tue, 16 Jun 2009 18:48:01 -0400 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> <1357820178.20090616140700@foucault.co.uk> Message-ID: <4A382121.1040201@gmail.com> The program is called InvRon for Inverse Ronchi, the more general name for this type of grating. I too learned about it from the Mobsby article in S&T. Mobsby uses an approximate method for calculating the gratings. Malacara and Cornejo describe a precise method of based on abberation theory. The calculations used in InvRon are made using ray tracing. The tricky part of making an Inverse Ronchi grating is the need to print or reduce it too a quite small, and very carefully controlled size. Mark Holm Nils Olof Carlin wrote: >> I believe there is a program for printing the pattern for a given >> mirror > > http://www.atmsite.org/contrib/Holm/invron/invron.html perhaps? > > Searching on google for "mobsby null test" gives some 180 hits, "mosby > null > test" 60 or so. "Mobsby" apparently is the correct version. > >>>> Who remembers Eric Mobsby's brilliant improvement to Ronchi? -- Mark Holm markholm at verizon.net holmmarkd at gmail.com From behambu at artinso.com Wed Jun 17 07:48:00 2009 From: behambu at artinso.com (Berthold Hamburger) Date: Wed, 17 Jun 2009 00:48:00 +0200 Subject: [ATM] Ronchi Grating Question In-Reply-To: <373798.53252.qm@web50106.mail.re2.yahoo.com> References: <373798.53252.qm@web50106.mail.re2.yahoo.com> Message-ID: <003e01c9eed4$812fca00$838f5e00$@com> The description for those screens is on my page courtesy Clint Bach who published it some 10 years ago. http://www.astro.artinso.com/ronchi.htm Let me use this to ask anybody who references to my previous site on Geocities that they update their links. My (hopelessly outdated) pages reside now on the server of my shop: http://www.astro.artinso.com I plan to revamp my astro site over the summer. 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 Mike Carambat > Sent: lunes, 15 de junio de 2009 17:21 > To: atm at atmlist.net > Subject: Re: [ATM] Ronchi Grating Question > > > Found instructions on DIY Ronchi screens on the internet some time back > but have lost the link. It acutally works quite well and makes better, > more pronounced shadows than the ones from Edmund! > > I used it to test one of those stupid 8" "parabolic" primary mirrors > they sell on Ebay. As I suspected, they were actually quite spherical, > not parabolic at all. > > You make the Ronchi gratings by cutting out two bars of 1/8" thick x > 1.5" wide aluminum strap to about 3" long and tape them together. Then > you drill a 1" hole in the middle through both bars. Now you've got two > plates of aluminum with a hole in the middle, still taped together. > > Now for the fun bit. You get two spools of ultra-light gauge > monofiliment from the Walmart thread and crafts department (sorry, can't > remember the gauge... I think it was 00, but not sure), spool off a few > inches from each spool and hold the threads side-by-side. tape them down > about 1/8" from the left side of the hole at the edge of the bottom of > the bar. > > Then begin wrapping your (still taped together) bars of aluminum about > with the two threads, holding both spools in your hand or make rig to > hold the spools and turn the bar instead. Go round and round, > perpendicular to the edge of the bars, two threads at a time, side by > side until you've made it completely across the hole and about 1/8" to > the right of the hole. This sounds easy, but is very time consuming and > requires a bit of dexterity. I think it took me about 45-60 minutes. > > The monofilment is hard to keep aligned as you work. I can't tell you > how many times I had to back up and start over. You should end of with a > perfect row of threads on both sides which do not overlap and do not > have many gaps between them (a few is ok, don't drive yourself > completely nuts). > > Now for the brilliant bit. Tape the end of one of the threads to the > bar. Take the other thread and UNWRAP it. This will leave a thread-wide > gap between each of the other threads. Ta-da! > > Use superglue or some other penetrating adhesive all around the holes on > both sides of your aluminum bars, coating the threads well. When dry, > simply cut through the threads and the tape along the edges of the bars > to seperate the two finished pieces. The glue will hold the threads in > place (hopefully). Now you've got two near exactly similiar Ronchi > screens! > > IMPORTANT NOTES: Try not to put too much tension on your wrappings. I > found that once the two plates were seperated at the end, the tension on > the threads really pulled at the glue and seperated them enmass from the > aluminum in a bunch at a few spots. I had to reseal it a few more times > with more glue. It could also be that aluminium simply isn't a good > surface to adhere monofilment to with superglue. Maybe something else, > maybe 1/8" plywood or even heavy cardboard. Dunno, experiment. > > Hope this helps! > > > > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From burrjaw at earthlink.net Wed Jun 17 08:15:12 2009 From: burrjaw at earthlink.net (Jim Burrows) Date: Tue, 16 Jun 2009 16:15:12 -0700 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <399241.27162.qm@web81906.mail.mud.yahoo.com> References: <399241.27162.qm@web81906.mail.mud.yahoo.com> Message-ID: At 2009-06-16 13:17 -0700, TONY BLAKESLEY wrote: >I did a search through the atmlist on the 2d hartmann test using a >webcam. The test seems accurate. Is the test hard to setup? Other >than making a "checkboard" mask, what is so difficult about it? Does >the test need precise measurment of various focal points? Anyone >have personal experience with this? Just place mask, shoot some >images, and let the computer analyze? It's probably unfair to say that I have a LOT of personal experience with the 2D webcam Hartmann test since I wrote the program. I made several checkerboard masks for mirrors up to 20" for the Telescope Optics Workshop (last one in 2002 ), so that's not too hard with a metal ruler and an X-ACTO knife. I think 1 mm accuracy of the measurements of source and image distances to the mirror is good enough, like for Foucault. I really had fun with the test when I used it for a non-null Hindle test of my RC cass secondary. In that version (unlike a primary mirror test) the major setup challenge was collimation to avoid test-induced astigmatism (I quite often cheated and estimated the primary astigmatism and said f'get it - it's just the test). 2D webcam Hartmann download: http://home.earthlink.net/~burrjaw/public/hart2d.zip (Win32, 2008-12-09, 1.15 MB) -- Jim Burrows -- http://home.earthlink.net/~burrjaw -- mailto:burrjaw at earthlink.net -- Seattle N47.4723 W122.3662 (WGS84) From rflrs at verizon.net Wed Jun 17 07:26:38 2009 From: rflrs at verizon.net (Richard F.L.R. Snashall) Date: Tue, 16 Jun 2009 18:26:38 -0400 Subject: [ATM] Triplet In-Reply-To: <4A2CDDAF.6010308@verizon.net> References: <3183d250711090321l23b17e67y71bc7189909483f8@mail.gmail.com> <920703.73390.qm@web82005.mail.mud.yahoo.com> <4A19EB73.40300@verizon.net> <4A2CDDAF.6010308@verizon.net> Message-ID: <4A381C1E.6090202@verizon.net> Richard F.L.R. Snashall wrote: > Richard F.L.R. Snashall wrote: >> >> The disadvantage here is that the spherochromatism >> is 2.7 to 3 times higher. > 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 > So, as long as you don't want to go deep into the UV, it is known that, except for that possible required trade-off between spherochromatism and lateral color, the special short flint triplet can reasonably compete with a fluorcrown triplet. The next step would be to attempt a split corrector refractor. I came up with (155 mm f/8): http://mysite.verizon.net/rflrs/Ptz12-36x.atm ATMOS input file http://mysite.verizon.net/rflrs/Ptz12-36x.len OSLO input file http://mysite.verizon.net/rflrs/Ptz12-36x.txt TEXT prescription http://mysite.verizon.net/rflrs/Ptz12-36x.zmx ZEMAX input file While it all-spherical, the problem is still variations of refractive index from the catalog data. Attempting to compensate for these variations with simple RoC and air-space changes again restricts the variations to better than grade 1 glass. In addition, the back focus, already tight at c. 73 mm, varied by over 15 mm in the corrected designs. However, if figuring the flat is allowed, almost all of this goes away. In fact, many of the optimized designs generated by the ZEMAX optimization of Monte Carlo samples actually were better than the original, and that includes freezing the back focus at the original design value. The fact that they can be better shouldn't be particularly surprising, as all-spherical designs are compromises in some respect, typically. Allowing for figuring of that surface simply eats away at those compromises. From holmmarkd at gmail.com Wed Jun 17 09:19:30 2009 From: holmmarkd at gmail.com (Mark Holm) Date: Tue, 16 Jun 2009 20:19:30 -0400 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <4A382121.1040201@gmail.com> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11> <1357820178.20090616140700@foucault.co.uk> <4A382121.1040201@gmail.com> Message-ID: <4A383692.8040200@gmail.com> Mark Holm wrote: > The program is called InvRon for Inverse Ronchi, the more general name > for this type of grating. I too learned about it from the Mobsby > article in S&T. Mobsby uses an approximate method for calculating the > gratings. Malacara and Cornejo describe a precise method of based on > abberation theory. The calculations used in InvRon are made using ray > tracing. > The ray tracing method should be "precise" and should allow accurate construction of gratings for faster mirrors and for other conics. It also allows for the fact that the grating will be off center in most practical setups. The thing to remember is that ray tracing is an approximation. Ronchi testing of any sort, really, any sort of optical testing, is fundamentally a kind of interferometry. The truly valid way to evaluate it mathematically, and the truly valid way to compute the gratings would be using wave optics. Unfortunately, I'm not up to that. Since others have pioneered and brought to a practical level, the Bath interferometer for computer assisted testing, If I were to invest the effort in a more sophisticated test method, I would adopt Bath, not Mobsby or it's more precise variants. This, even though I wrote the InvRon program. >> http://www.atmsite.org/contrib/Holm/invron/invron.html perhaps? >> >> > > -- Mark Holm markholm at verizon.net holmmarkd at gmail.com From richard1941 at gmail.com Wed Jun 17 10:40:31 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Tue, 16 Jun 2009 21:40:31 -0400 Subject: [ATM] Mosby and Ross Null comparo In-Reply-To: <003b01c9eec0$4b5baac0$5d9a5545@amd> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> Message-ID: <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> How come the backup mirror from Kodak was ok? I have previosly consulted for Perkin Elmer and found their management to be very political. They didn't care about system failure as long as they could not be blamed. Sent from my iPhone On Jun 16, 2009, at 16:23, "Bob May" wrote: >> From qhat I've heard on the Hubble mirror, that was an Offner > Null test that gave the wrong answer to the shape. The null > mirrors were spaced wrong as the mirror was different from the > military mirrors that the company was also making at the time and > the tester was borrowed from the military side and respaced for > the Hubble. Unfortunately, the tech doing the reassambly did the > job wrong. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Wed Jun 17 11:34:20 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Tue, 16 Jun 2009 19:34:20 -0700 Subject: [ATM] Mosby and Ross Null comparo In-Reply-To: <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> Message-ID: <001201c9eef4$272ef6f0$758ce4d0$@com> To call this a technical failure is disturbing. The technician's manager is responsible for his work. Company culture sets the environment for management. A poor company culture sets people up to fail, shifts blame and ignores risk. The example where one company succeeds and another fails is not something to ignore or blame on the muses. The 5 whys: http://en.wikipedia.org/wiki/5_Whys So many places to start with management: http://www.asq.org/quality-press/display-item/index.pl?item=P1228 Mel Bartels -----Original Message----- From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of Richard Schwartz Sent: Tuesday, June 16, 2009 6:41 PM To: Bob May Cc: Subject: Re: [ATM] Mosby and Ross Null comparo How come the backup mirror from Kodak was ok? I have previosly consulted for Perkin Elmer and found their management to be very political. They didn't care about system failure as long as they could not be blamed. Sent from my iPhone On Jun 16, 2009, at 16:23, "Bob May" wrote: >> From qhat I've heard on the Hubble mirror, that was an Offner > Null test that gave the wrong answer to the shape. The null > mirrors were spaced wrong as the mirror was different from the > military mirrors that the company was also making at the time and > the tester was borrowed from the military side and respaced for > the Hubble. Unfortunately, the tech doing the reassambly did the > job wrong. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ _______________________________________________ ATM mailing list http://www.atmlist.net/ From atmpob at yahoo.com Wed Jun 17 13:21:26 2009 From: atmpob at yahoo.com (Dale Eason) Date: Tue, 16 Jun 2009 21:21:26 -0700 (PDT) Subject: [ATM] H-Number Message-ID: <911709.57981.qm@web54505.mail.re2.yahoo.com> H number. I wonder on average how many replies it usually takes on an ATM list before the subject invariably changes to be about the failure of the Hubble mirror test. Could we call that the hubble number. Dale Eason From atmpob at yahoo.com Wed Jun 17 13:39:08 2009 From: atmpob at yahoo.com (Dale Eason) Date: Tue, 16 Jun 2009 21:39:08 -0700 (PDT) Subject: [ATM] H-Number Message-ID: <729880.83930.qm@web54502.mail.re2.yahoo.com> On further thought there probably is something similar to stellar evolution curve forn atm email threads. 1. They have too much mass with little interest and die out quickly. 2. They have more interest create a brief bust of activity but die out soon. 3. They create much interest and super nova into a new subjects that one of which can eventually be sucked into the hubble failure black hole. Dale Eason --- On Tue, 6/16/09, Dale Eason wrote: > From: Dale Eason > Subject: [ATM] H-Number > To: atm at atmlist.net > Date: Tuesday, June 16, 2009, 11:21 PM > > H number.? I wonder on average how many replies it > usually takes on an ATM list before the subject invariably > changes to be about the failure of the Hubble mirror test. > > Could we call that the hubble number. > > Dale Eason > > > ? ? ? > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From wallporritt at madasafish.com Wed Jun 17 15:36:30 2009 From: wallporritt at madasafish.com (John & Joyce) Date: Wed, 17 Jun 2009 07:36:30 +0100 Subject: [ATM] de register Message-ID: I wish to get out of the mailing list, I am not interested in chat room talk that clogs up my email box everytime I go on line. Please de -register me, I am no longer interested in the ATM site. John Wall. From vladimir.galogaza1 at zg.t-com.hr Wed Jun 17 17:26:48 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Wed, 17 Jun 2009 10:26:48 +0200 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <399241.27162.qm@web81906.mail.mud.yahoo.com> Message-ID: <6A14938F85774224B15CB4EA50A01BD7@piv555a133b59e> When James announced his 2D Hartmann test program I have tried it with Jims extensive support. Building the equipment was not difficult. I have used a bearing ball illuminated with bright LED for point source, and for mask I have used services of a shop with laser cutter. I have submitted disk with mask data (size of checkerboard squares and overall size) and they have made it from rubber sheet exactly on specifications. I still have it. But at that time, years ago, I missed computer power, mainly the memory amount, so the computing was either too long or failed. With what we have today it will be piece of cake. James, thanks again for your help and please have my best regards. Vladimir. ----- Original Message ----- From: "Jim Burrows" To: Sent: Wednesday, June 17, 2009 1:15 AM Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > At 2009-06-16 13:17 -0700, TONY BLAKESLEY wrote: > >>I did a search through the atmlist on the 2d hartmann test using a >>webcam. The test seems accurate. Is the test hard to setup? Other >>than making a "checkboard" mask, what is so difficult about it? Does >>the test need precise measurment of various focal points? Anyone >>have personal experience with this? Just place mask, shoot some >>images, and let the computer analyze? > > It's probably unfair to say that I have a LOT of personal experience > with the 2D webcam Hartmann test since I wrote the program. I made > several checkerboard masks for mirrors up to 20" for the Telescope > Optics Workshop (last one in 2002 ), so that's not too hard with > a metal ruler and an X-ACTO knife. I think 1 mm accuracy of the > measurements of source and image distances to the mirror is good > enough, like for Foucault. > > I really had fun with the test when I used it for a non-null Hindle > test of my RC cass secondary. In that version (unlike a primary > mirror test) the major setup challenge was collimation to avoid > test-induced astigmatism (I quite often cheated and estimated the > primary astigmatism and said f'get it - it's just the test). > > 2D webcam Hartmann download: > http://home.earthlink.net/~burrjaw/public/hart2d.zip > (Win32, 2008-12-09, 1.15 MB) > > -- 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/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.73/2180 - Release Date: 06/16/09 07:41:00 From camkit at mweb.co.za Wed Jun 17 17:21:45 2009 From: camkit at mweb.co.za (chris forder) Date: Wed, 17 Jun 2009 10:21:45 +0200 Subject: [ATM] Ronchi Grating Question Message-ID: <4A38A799.8080101@mweb.co.za> I prefer the Foucault test with a variation. The measurements are written onto the mirror with a whiteboard marker and are from top to bottom. This means you are measuring to an intersection of shadows rather than a transition of shadows (across the mirror) Chris Cape Town From vladimir.galogaza1 at zg.t-com.hr Wed Jun 17 19:13:27 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Wed, 17 Jun 2009 12:13:27 +0200 Subject: [ATM] fogging Message-ID: <634904F81AA7453FA1A9037AB177886D@piv555a133b59e> Perhaps this will be interesting for some. The Economist, June 13th, 2009, page 81. " A new, cheap way to stop glass from fogging." Team of scientists from the Chinese Academy of Sciences created anti-mist coating. Estimate is that square meter of glass will cost few cents to treat. Water vapor condenses into many tiny water droplets which scatter light. When certain nanoparticles are spread over glass, they break the surface tension of the water. The result is a thin transparent film of water which, unlike droplets, does not scatter light. They used polystyrene spheres treated with oxygen and than coated with silica to build raspberry like shapes most effective in preventing droplets formation. If this could work on telescope mirrors remains to be checked. Process is not commercialized yet. Regards Vladimir From dlwebb at canit.se Wed Jun 17 19:37:50 2009 From: dlwebb at canit.se (Dominic-Luc Webb) Date: Wed, 17 Jun 2009 12:37:50 +0200 (MET DST) Subject: [ATM] fogging In-Reply-To: <634904F81AA7453FA1A9037AB177886D@piv555a133b59e> Message-ID: On Wed, 17 Jun 2009, Vladimir Galogaza wrote: > The Economist, June 13th, 2009, page 81. > > " A new, cheap way to stop glass from fogging." > > Team of scientists from the Chinese Academy of Sciences created > anti-mist coating. Possibly. Shape and hydrophobicity are usual targets for this technology and this seems no different. The real test will be if this is suitable optically. The optical quality of any of our optics are massive overkill compared to what is needed for a car windshield. For the technologies I know of, the car windshield is the target market and the investigators don't care about our specific needs. The claim about a few cents per square meter suggests to me that the present investigators are catering to that same market. I guess if this material becomes available, we can try some optical tests, albeit, the names of the relevant authors and detailed contact info are not stated so far. Dominic From atmer at flash.net Wed Jun 17 21:39:49 2009 From: atmer at flash.net (Anthony Stillman) Date: Wed, 17 Jun 2009 05:39:49 -0700 (PDT) Subject: [ATM] de register Message-ID: <928824.10119.qm@web82001.mail.mud.yahoo.com> Well John I guess you've been on the list long enough that you've forgotten the contents of the message sent you when you joined. I know I have. How to unsubscribe is explained on the web where you signed up and of course many times in the ATM archive in response to all the others before you who threatened to take their ball and go home. The signal to noise ratio of THE list is actually quite high. Occasionally we get a talking to by the moderator but by in large THE list is well self moderated. That is, members who believe a thread is OT will write those perpetuating it either off list or on list and note as much. Usually threads which devolve into non telescope making related stuff quickly die out or move to a list oriented toward something called "observing", whatever that is. To bend this thread back toward telescope making, let me report that I am undertaking the making of a bimetal strip. One side made of high tin bronze, the other of red brass. Since theoretically these metals have the same coefficient of thermal expansion the strip needs to be long and any de-registration of it's mobile end will need to be measured carefully. I'm thinking a feeler gauge. Riveting the ends is turning out to be quite a challenge given the ridiculously brittle nature of the high tin bronze. My objective is to get some numbers and try a couple of different red brass alloys before I build a Rosse type light weighted specula. Anthony From jhissong at gmail.com Wed Jun 17 23:19:03 2009 From: jhissong at gmail.com (Jason Hissong) Date: Wed, 17 Jun 2009 10:19:03 -0400 Subject: [ATM] My 12.5" Ultralight Message-ID: Ron Ravneberg and I sat on the steps of Perkins Observatory 4 years ago talking about telescopes (I was just starting to get into ATMing at the time) and he said something to me that I have found very accurate when making your own telescopes: "A telescope you make is never really done." Right after I finished the 12.5" F4.3 mirror, I built a telescope based on a scaled up version of a ballscope design I did for my 8" F4.2 mirror I completed in 2005. I really liked the simplicity of this type of scope and even though there are design challenges associated with ballscopes, I was able to resolve most of them with the 8" scope. However, I have since learned that scaling up does not always work out. The design issues are larger and although I think I could have resolved them as well, I lost patience with the design (for now) and proceeded to try something I have not done before and that is to build a two axis based dobsonian telescope. I reused as much as I could (the secondary ring and truss system) and I think the results have exceeded my expectations. I finally have a scope that moves as smooth as the Obsession I used to own and now I can add all of the accessories that I wanted (dew system, right angle finder, etc). I documented the build of the scope on my blog if anyone is interested: http://undermidnight.blogspot.com Clear Skies, Jason Hissong From ericandroberta at sbcglobal.net Thu Jun 18 01:25:49 2009 From: ericandroberta at sbcglobal.net (D ERIC ALLEN) Date: Wed, 17 Jun 2009 09:25:49 -0700 (PDT) Subject: [ATM] atm: cassegrain software Message-ID: <439440.42551.qm@web80504.mail.mud.yahoo.com> Just finishing up my 24" f/4 primary.? I'm planning an f/4-f/12 classical cass with a Nasmyth-type tertiary?to put the eyepiece at eye level.? I'll probably need some CAD-type software for the telescope and some software to sort out the cassegrain parameters.? Something that would handle both would be great.? Any suggestions? Thanks Eric Allen From stainless_steel at suddenlink.net Thu Jun 18 04:33:42 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 14:33:42 -0500 Subject: [ATM] Betr.: Re: ATM: Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl><20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> Message-ID: Guys- As I remember it, the way the Mobsby test was used was to have the inverted (concave lines- i.e, lines converged towards the inside, diverging as they approached the edge of mirror- a smooth curve on both lines, with only two lines on the grating)- convex towards the center- and it was used close to the center of curvature inside, not outside C of C. It was very sensitive, as it was very close to C of C, and only showed two lines. A series of pictures was published illustrating this in Sky and Telescope. At least, this is how I remember things. It was a long time ago, and my Sky and Telescope magazines slowly disappeared. When the curve was right, the lines were straight. Anyway, that is my memory of things. I hauled a very large pile of them over to Sand Springs once in my PA-28; I had forgotten to turn both magnetos on, when I took off from the grass runway at Eagle's nest (80 Octane for the airplane there was only 58 cents per gallon- then it disappeared from the market and I had to us LL-100) and we barely cleared the power lines at the end of the runway, and that heavy pile of Sky and Telescopes did its part. After I cleared the power lines, I noticed, with a quick cockpit check, that I had forgotten to turn one of the magnetos on. I immediately turned it on, and the little PA-28 (N95207) surged ahead. I finally gave all the magazines away, all 30 years' worth of them. D-LZ130 P.S.- Can anyone tell me what else in ATM-ing Eric was famous for? It was important, and Sky and Telescope published SEVERAL stories about his experiments, PROGRESS with this new thing, asssociated with the subject of telescope mirrors made by amateurs. It had nothing to do with testing. What was it? "H-------- -----r". (clue) ----- Original Message ----- From: "Nils Olof Carlin" To: Sent: Tuesday, June 16, 2009 3:48 PM Subject: Re: [ATM] Betr.: Re: ATM: Eric Mobsby > Mel, > > >>>>> "pattern-matching" by eye is bound to fail >> >> Bound to fail? Gosh, my 13" f/3.0 was figured by pattern matching (as >> have been many dozens of mirrors of mine and my students over the >> years). >> So maybe better to say that it "can fail"? > > Could we say "may succeed"? What, if anything, did a Foucault test > say? > > Using a plain Ronchi grid, one thing one can do is calculate (Jim Burrows' > DIFFRACT should work, but so may other software) the relative positions of > the bands across the mirror face, and mark the centers on a pinstick > (Everest style) for 5 (or 7) bands. > Then when testing, move the stage until the outer pair of bands match > their > pins. Then, do the inner bands match theirs, too? If not, figuring isn't > right yet. Assuming the grid is inside the ROC (barrel-shaped bands) - if > the inner bands are inside their pins, it means undercorrection. (I hope I > got that right!) The bending of the bands will tell nothing more than that > about the correction. > This would be roughly equivalent to a 2 (or 3) zone Foucault test. > > Nils Olof > > > > >>From a children's book: What bird always succeeds? > > > > > > A toothless budgie > > _______________________________________________ > 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: 270.12.76/2183 - Release Date: 06/17/09 05:53:00 From stainless_steel at suddenlink.net Thu Jun 18 04:41:45 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 14:41:45 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> References: <399241.27162.qm@web81906.mail.mud.yahoo.com> <8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> Message-ID: <7D9C3BB8B2054E039EE5616A2128CB03@R101> Everybody: One of my readers devised a method of doing Foucault across the central vertical meridian. I still have his photograph and explanation of how it works; it is very elegant. Don't know how accurate. If someone wants to see this photograph of how he did this, I will locate it and send it in an html email. Very elegant- it may already be in an html email. I want to give him credit, for his elegant innovation. It will surprise you (I had no idea one could do this). If he reads this note, I wish he would check in with a post and identify himself for me, before I go looking for that focograph (very special focograph)- D-LZ130 ----- Original Message ----- From: "Stephen Koehler" To: "TONY BLAKESLEY" Cc: Sent: Tuesday, June 16, 2009 4:06 PM Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > Tony, > > Maybe someone can devise a Ronchi test image analyzer! >> > > Regarding computer-assisted analysis techniques, the following are the > ones > I have heard of. Each has its advantages and disadvantages. > > 1. Computer null finding of static Foucault images > + simple, uses standard foucault setup > - resolution similar to standard Foucault > - only across one diameter, so it can miss astigmatism > > 2. Automated Foucault > + much higher resolution than (1) > - still only across one diameter > - need to build accurate, automated platform movement > > 3. 2D Hartmann > + fairly simple equipment > + reads whole mirror surface > - still need accurate state positioning (like Foucault) > - fairly low resolution > - cutting the mask is tedious, and only works for one size of mirror > > 4. Bath interferometer > + high resolution over the entire surface > + no need for a stage that measures position > - a bit more complex equipment than the others, but not all that bad > - needs a stage that moves in x, y, and z. > > I'm not sure a Ronchi image analyzer would give you any benefits not > already > seen in these other methods. > > If you're interested in doing something more that Foucault, I would highly > recommend looking at the Bath interferometer. The optical parts can be > put > together for about $50. You do need a suitable camera (digital SLR or > modified webcam). There are two free analysis programs you can use to > process the images. There's a lot of information on the interferometer > Wiki, and on the Yahoo interferometry group. > > http://starryridge.com/mediawiki-1.9.1/index.php?title=Main_Page > -- > Steve Koehler > _______________________________________________ > 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: 270.12.76/2183 - Release Date: 06/17/09 05:53:00 From stainless_steel at suddenlink.net Thu Jun 18 04:49:18 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 14:49:18 -0500 Subject: [ATM] Ronchi Grating Question In-Reply-To: <20090616151523.6svbzpde2scsw8oo@mail.bbastrodesigns.com> References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com><000601c9eebe$f581ef20$5d9a5545@amd> <20090616151523.6svbzpde2scsw8oo@mail.bbastrodesigns.com> Message-ID: <419DB3AD8C1D46BCB4A5FBBC93192BBA@R101> Mel, everyone else: There is an article in one of the old Albert Ingalls about the testing of a 19" mirror for a large, German mounted (at that time, people were not bright enough to think of a Dobsonian mounting, which does not reqauire a masssive, useless counterweight)- in any case, the article included how to reduce the actual shape of the mirror from the Caustic test, and explained the caustic test in the process (NOT the Irwin Schroader article about same; this was a different article). It is in those books somewhere. I seem to remember Toronto in connection with the article. D-LZ130 ----- Original Message ----- From: To: Sent: Tuesday, June 16, 2009 4:15 PM Subject: Re: [ATM] Ronchi Grating Question >> When you get the experience with gratings, you can indeed do a >> fair job of getting the right shape. However, it is a subjective >> test in that regard and I wouldn't guarantee that you really have >> the "right" shape anywhere near as it could be determined by a >> Foucault test > > > Tell me, what makes an excellent optic, a good optic, a poor optic? > You cannot escape entering the subjective realm when describing visual > experiences. > > The idea that Foucault can determine the "right" shape is logically > impossible. > > The Bath interferometer (and similar) gets right to a comprehensive > Strehl/RMS, so with high probability can be mapped to subjective > experiences. > > As long as mirror testing is seen as an engineering issue and not a > human problem, the community will struggle with mysterious maladies > and mysteries. > > Mel Bartels > > > _______________________________________________ > 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: 270.12.76/2183 - Release Date: 06/17/09 05:53:00 From stainless_steel at suddenlink.net Thu Jun 18 05:19:19 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 15:19:19 -0500 Subject: [ATM] ATM: Found it! Eureka! Message-ID: <0A2DFDD7D8954EE0B7CBCA484280627D@R101> Folks: I found that small, but dramatically innovative picture of the Foucault test applied across a vertical meridian, with no modification of tester. Unfortunately, I do not have a record of who sent it. Someone 'fess up, please, to having invented this quite innovative idea. And it is anyone's who wants it in an html email. D-LZ130 From stainless_steel at suddenlink.net Thu Jun 18 05:20:11 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 15:20:11 -0500 Subject: [ATM] Betr.: Re: ATM: Eric Mobsby In-Reply-To: <20090616151934.29sfybj14w8o0g0g@mail.bbastrodesigns.com> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl><20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> <20090616151934.29sfybj14w8o0g0g@mail.bbastrodesigns.com> Message-ID: <13D260E77D594459BD4F0DCA97AC05AC@R101> I agree. D-LZ130 ----- Original Message ----- From: To: Sent: Tuesday, June 16, 2009 4:19 PM Subject: Re: [ATM] Betr.: Re: ATM: Eric Mobsby > That's not how I do the pattern matching Ronchi test. Get away from > the 'measuring' aspect and concentrate more on the qualitative > comparison. The human eye-brain is remarkably sensitive. Just > because it can't be measured doesn't mean that it's somehow inferior > or invalid or to be judged harshly. > > Mel Bartels > > > > Quoting Nils Olof Carlin : > >> Mel, >> >> >>>>>> "pattern-matching" by eye is bound to fail >>> >>> Bound to fail? Gosh, my 13" f/3.0 was figured by pattern matching (as >>> have been many dozens of mirrors of mine and my students over the >>> years). >>> So maybe better to say that it "can fail"? >> >> Could we say "may succeed"? What, if anything, did a Foucault test >> say? >> >> Using a plain Ronchi grid, one thing one can do is calculate (Jim >> Burrows' >> DIFFRACT should work, but so may other software) the relative positions >> of >> the bands across the mirror face, and mark the centers on a pinstick >> (Everest style) for 5 (or 7) bands. >> Then when testing, move the stage until the outer pair of bands match >> their >> pins. Then, do the inner bands match theirs, too? If not, figuring isn't >> right yet. Assuming the grid is inside the ROC (barrel-shaped bands) - if >> the inner bands are inside their pins, it means undercorrection. (I hope >> I >> got that right!) The bending of the bands will tell nothing more than >> that >> about the correction. >> This would be roughly equivalent to a 2 (or 3) zone Foucault test. >> >> Nils Olof >> >> >> >> >>> From a children's book: What bird always succeeds? >> >> >> >> >> >> A toothless budgie >> >> _______________________________________________ >> 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: 8.5.339 / Virus Database: 270.12.76/2183 - Release Date: 06/17/09 05:53:00 From stainless_steel at suddenlink.net Thu Jun 18 05:26:11 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 15:26:11 -0500 Subject: [ATM] Mosby and Ross Null comparo In-Reply-To: <20090616152437.rdwcha4mskw4sw8o@mail.bbastrodesigns.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com><1D11C9A894B348F9BA87F91996B7F7EA@R101><8CBBCD1F122170E-19C-1F59@FWM-D06.sysops.aol.com><74D5CDC6F889466498852C6B0CAAB6D1@R101> <20090616152437.rdwcha4mskw4sw8o@mail.bbastrodesigns.com> Message-ID: <238093CD4E9740EDBA6601BC6A385647@R101> You know something I don't, is all, Mel. Tell us, please. And do tell why they didn't borrow a 36" Celestron cinetheodolite, and use it as a collimator, and just shine it straight in the front of the assembled big telescope, and use a good old razor blade at the focus of the big scope, and simply null test the whole shebang. A 36" is a subaperture instrument, true- but large enough to span distance between edge of secondary, and edge of primary of Hubble. Ritchey figured 40" with subdiameter flats, quite successfully. Perkin Elmer made unnecessary excuses, if they could have won the game buy another method. I would have used a subaperture collimator. D-LZ130 ----- Original Message ----- From: To: Sent: Tuesday, June 16, 2009 4:24 PM Subject: Re: [ATM] Mosby and Ross Null comparo >> It was a modification of the null test at center of curvature that was >> used. A lens was out of position by a tiny bit. No lenses or mirrors in >> a Foucault tester. > > > And why was the lens out of position? That's a deeper reason for the > Hubble failure. Ask the 5 whys to get to the true root cause. > > Mel Bartels > > > _______________________________________________ > 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: 270.12.76/2183 - Release Date: 06/17/09 05:53:00 From rmay at nethere.com Thu Jun 18 05:33:19 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 13:33:19 -0700 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com> <000601c9eebe$f581ef20$5d9a5545@amd> Message-ID: <000801c9ef8a$da9e42e0$819a5545@amd> Nils, that is an interesting idea! Doing 5-7 lines will allow the pins to be easily seen in the middle of the lines displayed. It will, however, still not give a quantitive answer to how good the mirror is to the level that I expect (1/10th wave on the wavefront or better) but it will definitely tell if it is time to go to the Foucault test. Sorry that this isn't to your post directly as my computer took a barf and I had to restart. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From stainless_steel at suddenlink.net Thu Jun 18 05:30:53 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 15:30:53 -0500 Subject: [ATM] Fw: Ronchi Grating Question Message-ID: <0ECEC4D7EDDC411399282D6DF50E74AC@R101> Berthold- I could not find a picture of one of these screens on your site. But then, I am notoriously stupid. D-LZ130 ----- Original Message ----- From: "Berthold Hamburger" To: Cc: Sent: Tuesday, June 16, 2009 5:48 PM Subject: Re: [ATM] Ronchi Grating Question > The description for those screens is on my page courtesy Clint Bach who > published it some 10 years ago. > http://www.astro.artinso.com/ronchi.htm > > Let me use this to ask anybody who references to my previous site on > Geocities that they update their links. My (hopelessly outdated) pages > reside now on the server of my shop: http://www.astro.artinso.com > > I plan to revamp my astro site over the summer. > > 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 Mike Carambat >> Sent: lunes, 15 de junio de 2009 17:21 >> To: atm at atmlist.net >> Subject: Re: [ATM] Ronchi Grating Question >> >> >> Found instructions on DIY Ronchi screens on the internet some time back >> but have lost the link. It acutally works quite well and makes better, >> more pronounced shadows than the ones from Edmund! >> >> I used it to test one of those stupid 8" "parabolic" primary mirrors >> they sell on Ebay. As I suspected, they were actually quite spherical, >> not parabolic at all. >> >> You make the Ronchi gratings by cutting out two bars of 1/8" thick x >> 1.5" wide aluminum strap to about 3" long and tape them together. Then >> you drill a 1" hole in the middle through both bars. Now you've got two >> plates of aluminum with a hole in the middle, still taped together. >> >> Now for the fun bit. You get two spools of ultra-light gauge >> monofiliment from the Walmart thread and crafts department (sorry, can't >> remember the gauge... I think it was 00, but not sure), spool off a few >> inches from each spool and hold the threads side-by-side. tape them down >> about 1/8" from the left side of the hole at the edge of the bottom of >> the bar. >> >> Then begin wrapping your (still taped together) bars of aluminum about >> with the two threads, holding both spools in your hand or make rig to >> hold the spools and turn the bar instead. Go round and round, >> perpendicular to the edge of the bars, two threads at a time, side by >> side until you've made it completely across the hole and about 1/8" to >> the right of the hole. This sounds easy, but is very time consuming and >> requires a bit of dexterity. I think it took me about 45-60 minutes. >> >> The monofilment is hard to keep aligned as you work. I can't tell you >> how many times I had to back up and start over. You should end of with a >> perfect row of threads on both sides which do not overlap and do not >> have many gaps between them (a few is ok, don't drive yourself >> completely nuts). >> >> Now for the brilliant bit. Tape the end of one of the threads to the >> bar. Take the other thread and UNWRAP it. This will leave a thread-wide >> gap between each of the other threads. Ta-da! >> >> Use superglue or some other penetrating adhesive all around the holes on >> both sides of your aluminum bars, coating the threads well. When dry, >> simply cut through the threads and the tape along the edges of the bars >> to seperate the two finished pieces. The glue will hold the threads in >> place (hopefully). Now you've got two near exactly similiar Ronchi >> screens! >> >> IMPORTANT NOTES: Try not to put too much tension on your wrappings. I >> found that once the two plates were seperated at the end, the tension on >> the threads really pulled at the glue and seperated them enmass from the >> aluminum in a bunch at a few spots. I had to reseal it a few more times >> with more glue. It could also be that aluminium simply isn't a good >> surface to adhere monofilment to with superglue. Maybe something else, >> maybe 1/8" plywood or even heavy cardboard. Dunno, experiment. >> >> Hope this helps! >> >> >> >> >> >> >> _______________________________________________ >> 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: 8.5.339 / Virus Database: 270.12.76/2183 - Release Date: 06/17/09 05:53:00 From rmay at nethere.com Thu Jun 18 05:35:08 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 13:35:08 -0700 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com><000601c9eebe$f581ef20$5d9a5545@amd> Message-ID: <000d01c9ef8b$1b57c7c0$819a5545@amd> Yeppie. I often do that while testing to quickly see if the shape is sort of smooth. I will note that it, like all other tests, does take some experience to see what is going on. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Thu Jun 18 05:43:19 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 13:43:19 -0700 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <399241.27162.qm@web81906.mail.mud.yahoo.com> Message-ID: <001a01c9ef8c$401ef3c0$819a5545@amd> One of the guys that did a mirror at the class in Escondido had a program that took a series of about 10 photos of the mirror at a set of distances and then analyzed them. Don't know if that is the same program as he kind of indicated that he wrote it. The results of the program did come out close to a typical Foucault test and when I ran the Monte Carlo analysis on the Foucault results (TEX), the results of the Monte Carlo were peaked at about the same number. The only bad thing I found about the program is that it wanted a much higher resolution than a video image would produce so I never looked further into the program. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Thu Jun 18 05:51:35 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 13:51:35 -0700 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <399241.27162.qm@web81906.mail.mud.yahoo.com> <8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> Message-ID: <001d01c9ef8d$676b9220$819a5545@amd> 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 $20 is expensive for the casual amateur mirror maker) and the setup needs to be accurately done or theere is no reults to deal with. IN addition, cheap webcams and video (an expensive item all by themselves) really don't do that good of a job at reading the results for the accuracy that the test can resolve. A high megapixel camera is a lot better device to record the image. As such, I put that method of determining the mirror's shape out of the reach of the one time mirror maker, of which a fair number of people are. It is useful for a large class on mirror making to give a final result of a particular mirror that was made tho. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Thu Jun 18 05:54:36 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 13:54:36 -0700 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <399241.27162.qm@web81906.mail.mud.yahoo.com><8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> <7D9C3BB8B2054E039EE5616A2128CB03@R101> Message-ID: <002001c9ef8d$d3ae1c00$819a5545@amd> Almost everybody does the Foucault test in the horizontal direction but there is nothing in the test that says that you can't do a 90* V on the KE and take both horizontal and vertical tests at the same sitting. I've seen a page on this somewhere. You can even put the light source at the crotch of the V and do a slitless test setup. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From stainless_steel at suddenlink.net Thu Jun 18 05:59:53 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Wed, 17 Jun 2009 15:59:53 -0500 Subject: [ATM] Ronchi Grating Question In-Reply-To: <4A38A799.8080101@mweb.co.za> References: <4A38A799.8080101@mweb.co.za> Message-ID: <0FE828F5ED334F27B40B2ABC468DC453@R101> Chris, I think you are the man who sent me this "Foucault Test with a Variation" illustration. Thank you. One has already asked me for a copy of your vwery lucid illustration. I sent it with a superscription explanation in the message window. Would you like for me to send it to you? You're the man of the hour, with an original idea. I admire you for it. Well done. D-LZ130 ----- Original Message ----- From: "chris forder" To: Sent: Wednesday, June 17, 2009 3:21 AM Subject: Re: [ATM] Ronchi Grating Question >I prefer the Foucault test with a variation. The measurements are > written onto the mirror with a whiteboard marker and are from top to > bottom. This means you are measuring to an intersection of shadows > rather than a transition of shadows (across the mirror) > > Chris > Cape Town > > _______________________________________________ > 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: 270.12.76/2183 - Release Date: 06/17/09 05:53:00 From rmay at nethere.com Thu Jun 18 06:02:51 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 14:02:51 -0700 Subject: [ATM] ATM: Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> <002901c9eea5$b8babc70$2a303550$@de> Message-ID: <003101c9ef8e$fa52e1a0$819a5545@amd> I put all of the null tests to be in the qualitative type tests. I can determine the surface quality but not the shape for the most part. The only tests that I'd consider to be qualitative are the Foucault, caustic, Hartmann and interfrometer tests. Thes are the only tests that I know of that will actually determine the shape of the mirror without any reservations. The null tests all depend upon an aux. optic to convert the parabola (hopefully) to a spherical shape which is then measured. Place the nulling optics in the wrong place and you get a Hubble scope! Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Thu Jun 18 06:05:47 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 14:05:47 -0700 Subject: [ATM] H-Number References: <729880.83930.qm@web54502.mail.re2.yahoo.com> Message-ID: <004401c9ef8f$63407420$819a5545@amd> Veeerily Interesting! Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Thu Jun 18 06:11:53 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 14:11:53 -0700 Subject: [ATM] de register References: <928824.10119.qm@web82001.mail.mud.yahoo.com> Message-ID: <005701c9ef90$3d9565e0$819a5545@amd> I haven't gone and looked up what you are trying to do but I'd more use something like aluminum and a steel for a bimetallic strip. The difference in expansion is a lot larger and the metals take rivits easily. Another thing you can do is to solder the ends of the metals as both of them take solder well. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Thu Jun 18 06:14:57 2009 From: rmay at nethere.com (Bob May) Date: Wed, 17 Jun 2009 14:14:57 -0700 Subject: [ATM] atm: cassegrain software References: <439440.42551.qm@web80504.mail.mud.yahoo.com> Message-ID: <005e01c9ef90$ab525ac0$819a5545@amd> There is a cass calculator on the web which will produce the shapes and distancces needed. The mechanical work is not that hard to do and any cad program can be used to generate the drawings. I've got a copy of TurboCad (freeware) for that type of stuff. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From s.c.koehler at gmail.com Thu Jun 18 06:29:33 2009 From: s.c.koehler at gmail.com (Stephen Koehler) Date: Wed, 17 Jun 2009 16:29:33 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <001d01c9ef8d$676b9220$819a5545@amd> References: <399241.27162.qm@web81906.mail.mud.yahoo.com> <8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> <001d01c9ef8d$676b9220$819a5545@amd> Message-ID: <8d3a545d0906171429w277b858ct4c2e89aa9cc0a45d@mail.gmail.com> Bob, 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. I thoroughly agree. But, for someone who is considering one of the computer-assisted measuring techniques, the Bath interferometer is one of the more promising options. There is a bit of a learning curve to getting the interferometer functional and giving reliable results, but I have seen a number of people succeed on this path. -- Steve Koehler From b-hamburger at artinso.com Thu Jun 18 06:31:48 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Wed, 17 Jun 2009 23:31:48 +0200 Subject: [ATM] Fw: Ronchi Grating Question In-Reply-To: <0ECEC4D7EDDC411399282D6DF50E74AC@R101> References: <0ECEC4D7EDDC411399282D6DF50E74AC@R101> Message-ID: <002d01c9ef93$07a00b90$16e022b0$@com> Hi David, There is no picture. Clint did not provide one at the time he asked me to put the info on my page and I must confess that I never made one of those gratings, as I used to use the fishing line for (you guessed it) fishing instead. However I have not been fishing for years and there is a chance, I might wrap up some screens and post some pictures sometime soon. Quite frankly, from all ways to manufacture Ronchi screens, the method published by Gert Gottschalk (Gert, can you provide a link? I can't find it anymore on my PC) strikes me as very practical, economic and simple and also opens up a lot of possibilities to experiment with Mosby gratings etc., as you can basically print whatever pattern you want to test with. I still have to find someone locally in Spain who can produce those prints, though. Berthold > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of stainless_steel at suddenlink.net > Sent: mi?rcoles, 17 de junio de 2009 22:31 > To: ATM list > Subject: [ATM] Fw: Ronchi Grating Question > > > Berthold- > > I could not find a picture of one of these screens on your site. But > then, I > am notoriously stupid. > > D-LZ130 > > > ----- Original Message ----- > From: "Berthold Hamburger" > To: > Cc: > Sent: Tuesday, June 16, 2009 5:48 PM > Subject: Re: [ATM] Ronchi Grating Question > > > > The description for those screens is on my page courtesy Clint Bach > who > > published it some 10 years ago. > > http://www.astro.artinso.com/ronchi.htm > > > > Let me use this to ask anybody who references to my previous site on > > Geocities that they update their links. My (hopelessly outdated) pages > > reside now on the server of my shop: http://www.astro.artinso.com > > > > I plan to revamp my astro site over the summer. > > > > 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 Mike Carambat > >> Sent: lunes, 15 de junio de 2009 17:21 > >> To: atm at atmlist.net > >> Subject: Re: [ATM] Ronchi Grating Question > >> > >> > >> Found instructions on DIY Ronchi screens on the internet some time > back > >> but have lost the link. It acutally works quite well and makes > better, > >> more pronounced shadows than the ones from Edmund! > >> > >> I used it to test one of those stupid 8" "parabolic" primary mirrors > >> they sell on Ebay. As I suspected, they were actually quite > spherical, > >> not parabolic at all. > >> > >> You make the Ronchi gratings by cutting out two bars of 1/8" thick x > >> 1.5" wide aluminum strap to about 3" long and tape them together. > Then > >> you drill a 1" hole in the middle through both bars. Now you've got > two > >> plates of aluminum with a hole in the middle, still taped together. > >> > >> Now for the fun bit. You get two spools of ultra-light gauge > >> monofiliment from the Walmart thread and crafts department (sorry, > can't > >> remember the gauge... I think it was 00, but not sure), spool off a > few > >> inches from each spool and hold the threads side-by-side. tape them > down > >> about 1/8" from the left side of the hole at the edge of the bottom > of > >> the bar. > >> > >> Then begin wrapping your (still taped together) bars of aluminum > about > >> with the two threads, holding both spools in your hand or make rig to > >> hold the spools and turn the bar instead. Go round and round, > >> perpendicular to the edge of the bars, two threads at a time, side by > >> side until you've made it completely across the hole and about 1/8" > to > >> the right of the hole. This sounds easy, but is very time consuming > and > >> requires a bit of dexterity. I think it took me about 45-60 minutes. > >> > >> The monofilment is hard to keep aligned as you work. I can't tell you > >> how many times I had to back up and start over. You should end of > with a > >> perfect row of threads on both sides which do not overlap and do not > >> have many gaps between them (a few is ok, don't drive yourself > >> completely nuts). > >> > >> Now for the brilliant bit. Tape the end of one of the threads to the > >> bar. Take the other thread and UNWRAP it. This will leave a thread- > wide > >> gap between each of the other threads. Ta-da! > >> > >> Use superglue or some other penetrating adhesive all around the holes > on > >> both sides of your aluminum bars, coating the threads well. When dry, > >> simply cut through the threads and the tape along the edges of the > bars > >> to seperate the two finished pieces. The glue will hold the threads > in > >> place (hopefully). Now you've got two near exactly similiar Ronchi > >> screens! > >> > >> IMPORTANT NOTES: Try not to put too much tension on your wrappings. I > >> found that once the two plates were seperated at the end, the tension > on > >> the threads really pulled at the glue and seperated them enmass from > the > >> aluminum in a bunch at a few spots. I had to reseal it a few more > times > >> with more glue. It could also be that aluminium simply isn't a good > >> surface to adhere monofilment to with superglue. Maybe something > else, > >> maybe 1/8" plywood or even heavy cardboard. Dunno, experiment. > >> > >> Hope this helps! > >> > >> > >> > >> > >> > >> > >> _______________________________________________ > >> 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: 8.5.339 / Virus Database: 270.12.76/2183 - Release Date: > 06/17/09 > 05:53:00 > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From atmpob at yahoo.com Thu Jun 18 06:47:30 2009 From: atmpob at yahoo.com (Dale Eason) Date: Wed, 17 Jun 2009 14:47:30 -0700 (PDT) Subject: [ATM] webcam 2d hartmann test and foucault image analyzer Message-ID: <67456.29159.qm@web54507.mail.re2.yahoo.com> The laser usually can be gotten for less than $10. The beam splitter is $15. Web cams work fine for the analysis if the proper lens is used. Setup is no harder than a Foucualt setup. I only ever made one mirror from start to finish. So I guess I'm a one time mirror maker and I found the Bath very usefull. I called it my poor mans large collimation flat. It was almost as easy to use during figuring as a large auto collimation flat is and a lot cheaper. I could test the figure once it had cooled in less than 5 minutes. Making and using one is about the same effort as making and using the Foucault test. As I have said before and I still stand by that statement. Most atm mirror makers have a camera or web cam already that will work. Including you Bob. Your video setup will work fine for with it. Dale Eason --- On Wed, 6/17/09, Bob May wrote: > From: Bob May > Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > To: atm at atmlist.net > Date: Wednesday, June 17, 2009, 3:51 PM > 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 > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mick at liquidgold.eclipse.co.uk Thu Jun 18 06:56:50 2009 From: mick at liquidgold.eclipse.co.uk (Mick Dunn) Date: Wed, 17 Jun 2009 22:56:50 +0100 Subject: [ATM] Ronchi Grating Question Message-ID: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95> Anyone have the exact dimensions of the Willmann-Bell Ronchi gratings? Either the100lpi or the 85. Mick From jkoptic at juno.com Thu Jun 18 07:14:10 2009 From: jkoptic at juno.com (jkoptic) Date: Wed, 17 Jun 2009 15:14:10 -0700 Subject: [ATM] Ronchi Grating Question Message-ID: <20090617.151412.3492.0.jkoptic> The article is in "Amateur Telescope Making - Advanced" and starts on page 376 of my 1937 edition. Jarvis Krumbein On Wed, 17 Jun 2009 14:49:18 -0500 writes: > Mel, everyone else: > > There is an article in one of the old Albert Ingalls about the > testing of a > 19" mirror for a large, German mounted (at that time, people were > not bright > enough to think of a Dobsonian mounting, which does not reqauire a > masssive, > useless counterweight)- in any case, the article included how to > reduce the > actual shape of the mirror from the Caustic test, and explained the > caustic > test in the process (NOT the Irwin Schroader article about same; > this was a > different article). It is in those books somewhere. I seem to > remember > Toronto in connection with the article. > > D-LZ130 > > > ____________________________________________________________ You're never too old to date. Senior Dating. Click Here. http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTQbQZqn9P4UrnvHzqzUJETgSjs8dKLdN2xR9TSnl1OVVMVgNshdIE/ From baldjeff at comcast.net Thu Jun 18 08:10:37 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Wed, 17 Jun 2009 16:10:37 -0700 Subject: [ATM] Ronchi Grating Question References: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95> Message-ID: 2.125" by 2.125" JB Jeff and Glenda Baldwin Lathrop, CA www.agetawaylogcabin.com www.stocktonastro.org ----- Original Message ----- From: "Mick Dunn" To: Sent: Wednesday, June 17, 2009 2:56 PM Subject: [ATM] Ronchi Grating Question > Anyone have the exact dimensions of the Willmann-Bell Ronchi gratings? > Either the100lpi or the 85. > Mick > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From gary at gfphoto.com Thu Jun 18 10:31:26 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Wed, 17 Jun 2009 21:31:26 -0400 Subject: [ATM] Q's for Mel Bartels re: Oversize pitch tool with turntable? In-Reply-To: <001201c9eef4$272ef6f0$758ce4d0$@com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> Message-ID: <4A3998EE.5090802@gfphoto.com> Mel, I've been reading posts going back about twelve years (including answers to my previous questions - thanks) and your site, and probably missed it but was wondering if there is anything special to know about polishing using your oversize pitch tool method with a 3 RPM turntable? Right now it's a 9" f4.5 or so I'm getting ready to polish. You describe building up the plywood base with thin wood to form a convex surface - how carefully do you need to do that? Do you ever get any problems with moisture being released from the wood after the pitch is poured? I'm guessing not as I didn't see it mentioned and you specify high quality ply. For polishing out what stroke(s) do you use? And when you do say a 1/3W is that referenced to the center of the mirror? Thank you, Gary Fuchs From vladimir.galogaza1 at zg.t-com.hr Thu Jun 18 16:38:34 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Thu, 18 Jun 2009 09:38:34 +0200 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <399241.27162.qm@web81906.mail.mud.yahoo.com><8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> <001d01c9ef8d$676b9220$819a5545@amd> Message-ID: <6CAFB618A94D458499E36AA9DF6BD4F0@piv555a133b59e> 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 From vladimir.galogaza1 at zg.t-com.hr Thu Jun 18 16:55:37 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Thu, 18 Jun 2009 09:55:37 +0200 Subject: [ATM] Ronchi Grating Question References: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95> Message-ID: Hi Mick, >Anyone have the exact dimensions of the Willmann-Bell Ronchi gratings? 57x56 mm (exact to 0.1mm :-) Regards Vladimir. From nilsolof.carlin at telia.com Thu Jun 18 18:11:31 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Thu, 18 Jun 2009 11:11:31 +0200 Subject: [ATM] ATM: Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> <002901c9eea5$b8babc70$2a303550$@de> <003101c9ef8e$fa52e1a0$819a5545@amd> Message-ID: <27A3A4E7674A459D99F03BCBC95111A8@dittda7685d135> Bob wrote: > The only tests that I'd consider to be qualitative > are the Foucault, caustic, Hartmann and interfrometer tests. > Thes are the only tests that I know of that will actually > determine the shape of the mirror without any reservations. You wouldn't mean quantitative instead? I would add the lateral wire test to that collection. Nils Olof From nilsolof.carlin at telia.com Thu Jun 18 18:11:37 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Thu, 18 Jun 2009 11:11:37 +0200 Subject: [ATM] Ronchi Grating Question References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com><000601c9eebe$f581ef20$5d9a5545@amd> <000801c9ef8a$da9e42e0$819a5545@amd> Message-ID: > Nils, that is an interesting idea! Doing 5-7 lines will allow > the pins to be easily seen in the middle of the lines displayed. > It will, however, still not give a quantitive answer to how good > the mirror is to the level that I expect (1/10th wave on the > wavefront or better) but it will definitely tell if it is time to > go to the Foucault test. All the "Foucault class" tests (see another post) will determine the profile across the diameter used, to some approximation, depending on (among other things) the number of zones measured. Two zones measured will give the conic correction under the assumption that the figure is a conic or close to it (Sixtests and Figure (-XP) will supply the best fit conic constant, if asked for). The 5-line Ronchi test that I suggested should give you two quantitative zonal measures with good resolution, but only qualitative information on irregularities of other kinds. With seven bands, you could estimate low-order sph abb. One critical factor with Ronchi-type tests is the accurate position of the grid, with respect to the best paraxial ROC. The method I suggest would have the advantage of critically defining the (longitudinal) position. Nils Olof From nilsolof.carlin at telia.com Thu Jun 18 18:42:44 2009 From: nilsolof.carlin at telia.com (Nils Olof Carlin) Date: Thu, 18 Jun 2009 11:42:44 +0200 Subject: [ATM] : Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl><20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> <20090616151934.29sfybj14w8o0g0g@mail.bbastrodesigns.com> Message-ID: Mel, > That's not how I do the pattern matching Ronchi test. Get away from the > 'measuring' aspect and concentrate more on the qualitative comparison. > The human eye-brain is remarkably sensitive. Just because it can't be > measured doesn't mean that it's somehow inferior or invalid or to be > judged harshly. It is also remarkably easy to dupe, as any quick search for "optical illusions" will demonstrate. But for unfortunate geographical circumstances, I would love to join one of your mirror making class, but I have of course no first-hand comments about your mirrors. BTW, just how do you match the Ronchi patterns? Nils Olof From toliman at wave.co.nz Thu Jun 18 19:02:10 2009 From: toliman at wave.co.nz (Malcolm McDonald) Date: Thu, 18 Jun 2009 22:02:10 +1200 Subject: [ATM] Sealed Lead Battery References: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95> Message-ID: <04F86341EC36433BBAD5EBF507633C15@Grandad> I have recently bought a battery to power the drive mechanism for my equatorial 16"scope. The drive that I am working on is a rather unorthadox design that I dreamed up, where the whole motor, battery, and drive mechanism revolve around a fixed shaft. ie the battery will be rotating and likely be left in any position. the battery measures 4x2x1 1/2 ins. Info printed on the case :- DiaMec Non-spillable sealed Rechargeable Battery DM12- 1.3 (12v1.3AH/20HR) My question is, does Non Spillable mean that it won't leak if you tip it over, or does it mean that it can be used and left in any position? Malcolm. From richard1941 at gmail.com Fri Jun 19 00:17:37 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Thu, 18 Jun 2009 11:17:37 -0400 Subject: [ATM] : Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl><20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> <20090616151934.29sfybj14w8o0g0g@mail.bbastrodesigns.com> Message-ID: "The human eye-brain is remarkably sensitive. Just because it can't be measured doesn't mean that it's somehow inferior or invalid or to be judged harshly." This is the basis of quack antiscience "vibrational medicine" such as homeopathy, theraputic touch, naturopathy, accupuncture, intercessionary prayer, aroma therapy, and ann that spooky stuff. > From richard1941 at gmail.com Fri Jun 19 00:21:41 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Thu, 18 Jun 2009 11:21:41 -0400 Subject: [ATM] Ronchi Grating Question In-Reply-To: References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com><000601c9eebe$f581ef20$5d9a5545@amd> <000801c9ef8a$da9e42e0$819a5545@amd> Message-ID: <1F40300E-EC0F-483A-9EF0-AA75B80F3B59@gmail.com> Hoy can view the profile directly with the foucault setup. Just cut the knife info the light cine and observe the shadow. Sent from my iPhone On Jun 18, 2009, at 5:11, "Nils Olof Carlin" wrote: >> Nils, that is an interesting idea! Doing 5-7 lines will allow >> the pins to be easily seen in the middle of the lines displayed. >> It will, however, still not give a quantitive answer to how good >> the mirror is to the level that I expect (1/10th wave on the >> wavefront or better) but it will definitely tell if it is time to >> go to the Foucault test. > > All the "Foucault class" tests (see another post) will determine the > profile across the diameter used, to some approximation, depending > on (among other things) the number of zones measured. Two zones > measured will give the conic correction under the assumption that > the figure is a conic or close to it (Sixtests and Figure (-XP) will > supply the best fit conic constant, if asked for). The 5-line Ronchi > test that I suggested should give you two quantitative zonal > measures with good resolution, but only qualitative information on > irregularities of other kinds. With seven bands, you could estimate > low-order sph abb. > One critical factor with Ronchi-type tests is the accurate position > of the grid, with respect to the best paraxial ROC. The method I > suggest would have the advantage of critically defining the > (longitudinal) position. > > Nils Olof > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From stainless_steel at suddenlink.net Fri Jun 19 01:32:38 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 11:32:38 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <003101c9ef8e$fa52e1a0$819a5545@amd> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> <002901c9eea5$b8babc70$2a303550$@de> <003101c9ef8e$fa52e1a0$819a5545@amd> Message-ID: Yes! D-LZ130 ----- Original Message ----- From: "Bob May" To: Sent: Wednesday, June 17, 2009 4:02 PM Subject: Re: [ATM] ATM: Eric Mobsby >I put all of the null tests to be in the qualitative type tests. > I can determine the surface quality but not the shape for the > most part. The only tests that I'd consider to be qualitative > are the Foucault, caustic, Hartmann and interfrometer tests. > Thes are the only tests that I know of that will actually > determine the shape of the mirror without any reservations. The > null tests all depend upon an aux. optic to convert the parabola > (hopefully) to a spherical shape which is then measured. Place > the nulling optics in the wrong place and you get a Hubble scope! > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > 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 From stainless_steel at suddenlink.net Fri Jun 19 01:34:31 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 11:34:31 -0500 Subject: [ATM] de register In-Reply-To: <005701c9ef90$3d9565e0$819a5545@amd> References: <928824.10119.qm@web82001.mail.mud.yahoo.com> <005701c9ef90$3d9565e0$819a5545@amd> Message-ID: Just trying to make a couple happy with their circumstances. D-LZ130 ----- Original Message ----- From: "Bob May" To: Sent: Wednesday, June 17, 2009 4:11 PM Subject: Re: [ATM] de register >I haven't gone and looked up what you are trying to do but I'd > more use something like aluminum and a steel for a bimetallic > strip. The difference in expansion is a lot larger and the > metals take rivits easily. > Another thing you can do is to solder the ends of the metals as > both of them take solder well. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > 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 From stainless_steel at suddenlink.net Fri Jun 19 01:41:10 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 11:41:10 -0500 Subject: [ATM] Fw: Ronchi Grating Question In-Reply-To: <002d01c9ef93$07a00b90$16e022b0$@com> References: <0ECEC4D7EDDC411399282D6DF50E74AC@R101> <002d01c9ef93$07a00b90$16e022b0$@com> Message-ID: <3CC4ECE3C65F49BABE2D774DC28D3818@R101> Thank you, Berthold. This is enlightening. D-LZ130 ----- Original Message ----- From: "Berthold Hamburger" To: Sent: Wednesday, June 17, 2009 4:31 PM Subject: Re: [ATM] Fw: Ronchi Grating Question Hi David, There is no picture. Clint did not provide one at the time he asked me to put the info on my page and I must confess that I never made one of those gratings, as I used to use the fishing line for (you guessed it) fishing instead. However I have not been fishing for years and there is a chance, I might wrap up some screens and post some pictures sometime soon. Quite frankly, from all ways to manufacture Ronchi screens, the method published by Gert Gottschalk (Gert, can you provide a link? I can't find it anymore on my PC) strikes me as very practical, economic and simple and also opens up a lot of possibilities to experiment with Mosby gratings etc., as you can basically print whatever pattern you want to test with. I still have to find someone locally in Spain who can produce those prints, though. Berthold > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of stainless_steel at suddenlink.net > Sent: mi?rcoles, 17 de junio de 2009 22:31 > To: ATM list > Subject: [ATM] Fw: Ronchi Grating Question > > > Berthold- > > I could not find a picture of one of these screens on your site. But > then, I > am notoriously stupid. > > D-LZ130 > > > ----- Original Message ----- > From: "Berthold Hamburger" > To: > Cc: > Sent: Tuesday, June 16, 2009 5:48 PM > Subject: Re: [ATM] Ronchi Grating Question > > > > The description for those screens is on my page courtesy Clint Bach > who > > published it some 10 years ago. > > http://www.astro.artinso.com/ronchi.htm > > > > Let me use this to ask anybody who references to my previous site on > > Geocities that they update their links. My (hopelessly outdated) pages > > reside now on the server of my shop: http://www.astro.artinso.com > > > > I plan to revamp my astro site over the summer. > > > > 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 Mike Carambat > >> Sent: lunes, 15 de junio de 2009 17:21 > >> To: atm at atmlist.net > >> Subject: Re: [ATM] Ronchi Grating Question > >> > >> > >> Found instructions on DIY Ronchi screens on the internet some time > back > >> but have lost the link. It acutally works quite well and makes > better, > >> more pronounced shadows than the ones from Edmund! > >> > >> I used it to test one of those stupid 8" "parabolic" primary mirrors > >> they sell on Ebay. As I suspected, they were actually quite > spherical, > >> not parabolic at all. > >> > >> You make the Ronchi gratings by cutting out two bars of 1/8" thick x > >> 1.5" wide aluminum strap to about 3" long and tape them together. > Then > >> you drill a 1" hole in the middle through both bars. Now you've got > two > >> plates of aluminum with a hole in the middle, still taped together. > >> > >> Now for the fun bit. You get two spools of ultra-light gauge > >> monofiliment from the Walmart thread and crafts department (sorry, > can't > >> remember the gauge... I think it was 00, but not sure), spool off a > few > >> inches from each spool and hold the threads side-by-side. tape them > down > >> about 1/8" from the left side of the hole at the edge of the bottom > of > >> the bar. > >> > >> Then begin wrapping your (still taped together) bars of aluminum > about > >> with the two threads, holding both spools in your hand or make rig to > >> hold the spools and turn the bar instead. Go round and round, > >> perpendicular to the edge of the bars, two threads at a time, side by > >> side until you've made it completely across the hole and about 1/8" > to > >> the right of the hole. This sounds easy, but is very time consuming > and > >> requires a bit of dexterity. I think it took me about 45-60 minutes. > >> > >> The monofilment is hard to keep aligned as you work. I can't tell you > >> how many times I had to back up and start over. You should end of > with a > >> perfect row of threads on both sides which do not overlap and do not > >> have many gaps between them (a few is ok, don't drive yourself > >> completely nuts). > >> > >> Now for the brilliant bit. Tape the end of one of the threads to the > >> bar. Take the other thread and UNWRAP it. This will leave a thread- > wide > >> gap between each of the other threads. Ta-da! > >> > >> Use superglue or some other penetrating adhesive all around the holes > on > >> both sides of your aluminum bars, coating the threads well. When dry, > >> simply cut through the threads and the tape along the edges of the > bars > >> to seperate the two finished pieces. The glue will hold the threads > in > >> place (hopefully). Now you've got two near exactly similiar Ronchi > >> screens! > >> > >> IMPORTANT NOTES: Try not to put too much tension on your wrappings. I > >> found that once the two plates were seperated at the end, the tension > on > >> the threads really pulled at the glue and seperated them enmass from > the > >> aluminum in a bunch at a few spots. I had to reseal it a few more > times > >> with more glue. It could also be that aluminium simply isn't a good > >> surface to adhere monofilment to with superglue. Maybe something > else, > >> maybe 1/8" plywood or even heavy cardboard. Dunno, experiment. > >> > >> Hope this helps! > >> > >> > >> > >> > >> > >> > >> _______________________________________________ > >> 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: 8.5.339 / Virus Database: 270.12.76/2183 - Release Date: > 06/17/09 > 05:53:00 > > _______________________________________________ > 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: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: 06/18/09 05:53:00 From stainless_steel at suddenlink.net Fri Jun 19 01:47:24 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 11:47:24 -0500 Subject: [ATM] Fw: Ronchi Grating Question In-Reply-To: <002d01c9ef93$07a00b90$16e022b0$@com> References: <0ECEC4D7EDDC411399282D6DF50E74AC@R101> <002d01c9ef93$07a00b90$16e022b0$@com> Message-ID: <8532E0C2A751447DBE3B413699E35962@R101> Thank you. D-LZ120 ----- Original Message ----- From: "Berthold Hamburger" To: Sent: Wednesday, June 17, 2009 4:31 PM Subject: Re: [ATM] Fw: Ronchi Grating Question Hi David, There is no picture. Clint did not provide one at the time he asked me to put the info on my page and I must confess that I never made one of those gratings, as I used to use the fishing line for (you guessed it) fishing instead. However I have not been fishing for years and there is a chance, I might wrap up some screens and post some pictures sometime soon. Quite frankly, from all ways to manufacture Ronchi screens, the method published by Gert Gottschalk (Gert, can you provide a link? I can't find it anymore on my PC) strikes me as very practical, economic and simple and also opens up a lot of possibilities to experiment with Mosby gratings etc., as you can basically print whatever pattern you want to test with. I still have to find someone locally in Spain who can produce those prints, though. Berthold > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of stainless_steel at suddenlink.net > Sent: mi?rcoles, 17 de junio de 2009 22:31 > To: ATM list > Subject: [ATM] Fw: Ronchi Grating Question > > > Berthold- > > I could not find a picture of one of these screens on your site. But > then, I > am notoriously stupid. > > D-LZ130 > > > ----- Original Message ----- > From: "Berthold Hamburger" > To: > Cc: > Sent: Tuesday, June 16, 2009 5:48 PM > Subject: Re: [ATM] Ronchi Grating Question > > > > The description for those screens is on my page courtesy Clint Bach > who > > published it some 10 years ago. > > http://www.astro.artinso.com/ronchi.htm > > > > Let me use this to ask anybody who references to my previous site on > > Geocities that they update their links. My (hopelessly outdated) pages > > reside now on the server of my shop: http://www.astro.artinso.com > > > > I plan to revamp my astro site over the summer. > > > > 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 Mike Carambat > >> Sent: lunes, 15 de junio de 2009 17:21 > >> To: atm at atmlist.net > >> Subject: Re: [ATM] Ronchi Grating Question > >> > >> > >> Found instructions on DIY Ronchi screens on the internet some time > back > >> but have lost the link. It acutally works quite well and makes > better, > >> more pronounced shadows than the ones from Edmund! > >> > >> I used it to test one of those stupid 8" "parabolic" primary mirrors > >> they sell on Ebay. As I suspected, they were actually quite > spherical, > >> not parabolic at all. > >> > >> You make the Ronchi gratings by cutting out two bars of 1/8" thick x > >> 1.5" wide aluminum strap to about 3" long and tape them together. > Then > >> you drill a 1" hole in the middle through both bars. Now you've got > two > >> plates of aluminum with a hole in the middle, still taped together. > >> > >> Now for the fun bit. You get two spools of ultra-light gauge > >> monofiliment from the Walmart thread and crafts department (sorry, > can't > >> remember the gauge... I think it was 00, but not sure), spool off a > few > >> inches from each spool and hold the threads side-by-side. tape them > down > >> about 1/8" from the left side of the hole at the edge of the bottom > of > >> the bar. > >> > >> Then begin wrapping your (still taped together) bars of aluminum > about > >> with the two threads, holding both spools in your hand or make rig to > >> hold the spools and turn the bar instead. Go round and round, > >> perpendicular to the edge of the bars, two threads at a time, side by > >> side until you've made it completely across the hole and about 1/8" > to > >> the right of the hole. This sounds easy, but is very time consuming > and > >> requires a bit of dexterity. I think it took me about 45-60 minutes. > >> > >> The monofilment is hard to keep aligned as you work. I can't tell you > >> how many times I had to back up and start over. You should end of > with a > >> perfect row of threads on both sides which do not overlap and do not > >> have many gaps between them (a few is ok, don't drive yourself > >> completely nuts). > >> > >> Now for the brilliant bit. Tape the end of one of the threads to the > >> bar. Take the other thread and UNWRAP it. This will leave a thread- > wide > >> gap between each of the other threads. Ta-da! > >> > >> Use superglue or some other penetrating adhesive all around the holes > on > >> both sides of your aluminum bars, coating the threads well. When dry, > >> simply cut through the threads and the tape along the edges of the > bars > >> to seperate the two finished pieces. The glue will hold the threads > in > >> place (hopefully). Now you've got two near exactly similiar Ronchi > >> screens! > >> > >> IMPORTANT NOTES: Try not to put too much tension on your wrappings. I > >> found that once the two plates were seperated at the end, the tension > on > >> the threads really pulled at the glue and seperated them enmass from > the > >> aluminum in a bunch at a few spots. I had to reseal it a few more > times > >> with more glue. It could also be that aluminium simply isn't a good > >> surface to adhere monofilment to with superglue. Maybe something > else, > >> maybe 1/8" plywood or even heavy cardboard. Dunno, experiment. > >> > >> Hope this helps! > >> > >> > >> > >> > >> > >> > >> _______________________________________________ > >> 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: 8.5.339 / Virus Database: 270.12.76/2183 - Release Date: > 06/17/09 > 05:53:00 > > _______________________________________________ > 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: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: 06/18/09 05:53:00 From stainless_steel at suddenlink.net Fri Jun 19 01:50:56 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 11:50:56 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <67456.29159.qm@web54507.mail.re2.yahoo.com> References: <67456.29159.qm@web54507.mail.re2.yahoo.com> Message-ID: <1D09FD89BC994E6CB22FCA18FC630B07@R101> Thank you, Dale. It has not occurred to almost any amateur that one may use a SUBDIAMeTER FLAT for autocollimation. All one needs to do is have a flat that extends from the edge of the secondary to the edge of the primary. Please, does anyone know about this? HAS ANYONE EVER HEARD OF HOW RITCHEY USED SUBDIAMTER FLATS TO FIGURE THE 40"? D-LZ130 ----- Original Message ----- From: "Dale Eason" To: Sent: Wednesday, June 17, 2009 4:47 PM Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer The laser usually can be gotten for less than $10. The beam splitter is $15. Web cams work fine for the analysis if the proper lens is used. Setup is no harder than a Foucualt setup. I only ever made one mirror from start to finish. So I guess I'm a one time mirror maker and I found the Bath very usefull. I called it my poor mans large collimation flat. It was almost as easy to use during figuring as a large auto collimation flat is and a lot cheaper. I could test the figure once it had cooled in less than 5 minutes. Making and using one is about the same effort as making and using the Foucault test. As I have said before and I still stand by that statement. Most atm mirror makers have a camera or web cam already that will work. Including you Bob. Your video setup will work fine for with it. Dale Eason --- On Wed, 6/17/09, Bob May wrote: > From: Bob May > Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > To: atm at atmlist.net > Date: Wednesday, June 17, 2009, 3:51 PM > 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 > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.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: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: 06/18/09 05:53:00 From stainless_steel at suddenlink.net Fri Jun 19 02:02:42 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 12:02:42 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <6CAFB618A94D458499E36AA9DF6BD4F0@piv555a133b59e> References: <399241.27162.qm@web81906.mail.mud.yahoo.com><8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com><001d01c9ef8d$676b9220$819a5545@amd> <6CAFB618A94D458499E36AA9DF6BD4F0@piv555a133b59e> Message-ID: <2FF94E4CDB5E43ACA74994141E9F4EE3@R101> 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 Fri Jun 19 02:04:03 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 12:04:03 -0500 Subject: [ATM] Foucault on a vertical axis In-Reply-To: <4A39F6D4.2080908@mweb.co.za> References: <4A39F6D4.2080908@mweb.co.za> Message-ID: <2DE353EDE0894255B149DC243DB7E3E6@R101> Thank you, Chris. I never throw anything away, that is useful. D-LZ130 ----- Original Message ----- From: "chris forder" To: Sent: Thursday, June 18, 2009 3:12 AM Subject: Foucault on a vertical axis > Hi D-LZ130 > > I sent you that memo about a year or so ago. > > Go Well > > Chris > Cape Town > -------------------------------------------------------------------------------- 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 From stainless_steel at suddenlink.net Fri Jun 19 02:05:48 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 12:05:48 -0500 Subject: [ATM] Ronchi Grating Question In-Reply-To: <4A39F7AB.8010503@mweb.co.za> References: <4A38A799.8080101@mweb.co.za> <0FE828F5ED334F27B40B2ABC468DC453@R101> <4A39F7AB.8010503@mweb.co.za> Message-ID: Thank you, Chris!!!!!!!!!!! D-LZ130 ----- Original Message ----- From: "chris forder" To: Sent: Thursday, June 18, 2009 3:15 AM Subject: Re: [ATM] Ronchi Grating Question > D-LZ130, > > Plase send it on to anyone who wants it, > Regards > Chris >> >> >> > > -------------------------------------------------------------------------------- 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 From stainless_steel at suddenlink.net Fri Jun 19 02:07:47 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 12:07:47 -0500 Subject: [ATM] ATM: Eric Mobsby In-Reply-To: <27A3A4E7674A459D99F03BCBC95111A8@dittda7685d135> References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> <002901c9eea5$b8babc70$2a303550$@de><003101c9ef8e$fa52e1a0$819a5545@amd> <27A3A4E7674A459D99F03BCBC95111A8@dittda7685d135> Message-ID: <9D3E3C76F9204C009DECFCC917F4D03A@R101> The lateral wire test is integral to the Caustic (Gaviola/Platzeck test)- D-LZ130 ----- Original Message ----- From: "Nils Olof Carlin" To: "Bob May" ; Sent: Thursday, June 18, 2009 4:11 AM Subject: Re: [ATM] ATM: Eric Mobsby > > Bob wrote: >> The only tests that I'd consider to be qualitative >> are the Foucault, caustic, Hartmann and interfrometer tests. >> Thes are the only tests that I know of that will actually >> determine the shape of the mirror without any reservations. > > You wouldn't mean quantitative instead? > I would add the lateral wire test to that collection. > > Nils Olof > _______________________________________________ > 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 From stainless_steel at suddenlink.net Fri Jun 19 02:12:37 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 12:12:37 -0500 Subject: [ATM] Ronchi Grating Question In-Reply-To: References: <000f01c9ec78$3a205d40$a9fe1345@amd><7F87286500D843538529A4E8A9ED6A6C@dittda7685d135><2015F9C887DC45F39DABF13D249AE59A@dittda7685d135><20090616133529.6zfkyx39ew4okg84@mail.bbastrodesigns.com><000601c9eebe$f581ef20$5d9a5545@amd><000801c9ef8a$da9e42e0$819a5545@amd> Message-ID: "Turpcicerie" (Not Nils' answer, but the rest of the post) D-LZ130 1/10th is the limit of accuraracy is the limit of Foucualt, by the masters. ----- Original Message ----- From: "Nils Olof Carlin" To: "Bob May" ; Sent: Thursday, June 18, 2009 4:11 AM Subject: Re: [ATM] Ronchi Grating Question >> Nils, that is an interesting idea! Doing 5-7 lines will allow >> the pins to be easily seen in the middle of the lines displayed. >> It will, however, still not give a quantitive answer to how good >> the mirror is to the level that I expect (1/10th wave on the >> wavefront or better) but it will definitely tell if it is time to >> go to the Foucault test. > > All the "Foucault class" tests (see another post) will determine the > profile > across the diameter used, to some approximation, depending on (among other > things) the number of zones measured. Two zones measured will give the > conic > correction under the assumption that the figure is a conic or close to it > (Sixtests and Figure (-XP) will supply the best fit conic constant, if > asked > for). The 5-line Ronchi test that I suggested should give you two > quantitative zonal measures with good resolution, but only qualitative > information on irregularities of other kinds. With seven bands, you could > estimate low-order sph abb. > One critical factor with Ronchi-type tests is the accurate position of the > grid, with respect to the best paraxial ROC. The method I suggest would > have > the advantage of critically defining the (longitudinal) position. > > Nils Olof > > > _______________________________________________ > 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 From jbentz at inreach.com Fri Jun 19 02:16:55 2009 From: jbentz at inreach.com (Jan Bentz) Date: Thu, 18 Jun 2009 10:16:55 -0700 Subject: [ATM] Sealed Lead Battery In-Reply-To: <04F86341EC36433BBAD5EBF507633C15@Grandad> References: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95> <04F86341EC36433BBAD5EBF507633C15@Grandad> Message-ID: <4A3A7687.4060406@inreach.com> Malcolm McDonald wrote: > I have recently bought a battery to power the drive mechanism for my > equatorial 16"scope. The drive that I am working on is a rather > unorthadox design that I dreamed up, where the whole motor, battery, > and drive mechanism revolve around a fixed shaft. ie the battery will > be rotating and likely be left in any position. > > the battery measures 4x2x1 1/2 ins. > > Info printed on the case :- DiaMec > Non-spillable sealed Rechargeable > Battery > DM12- 1.3 (12v1.3AH/20HR) > > My question is, does Non Spillable mean that it won't leak if you tip > it over, or does it mean that it can be used and left in any position? > > Malcolm. > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > Malcolm -- If you need more capacity than what you have try a sealed battery intended for an open wheel racing car. They will work upside down and even survive heavy shock loads. They are much lighter and smaller than your average car battery but they ain't cheap. Jan Bentz From stainless_steel at suddenlink.net Fri Jun 19 02:18:13 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 12:18:13 -0500 Subject: [ATM] Sealed Lead Battery In-Reply-To: <04F86341EC36433BBAD5EBF507633C15@Grandad> References: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95> <04F86341EC36433BBAD5EBF507633C15@Grandad> Message-ID: <3E46BC7A0B614B19BB6B862F3645C7C8@R101> http://www.atmsite.org/contrib/Harbour/SectorDrive.html http://www.atmsite.org/contrib/Harbour/Brngz.html ----- Original Message ----- From: "Malcolm McDonald" To: Sent: Thursday, June 18, 2009 5:02 AM Subject: Re: [ATM] Sealed Lead Battery >I have recently bought a battery to power the drive mechanism for my > equatorial 16"scope. The drive that I am working on is a rather unorthadox > design that I dreamed up, where the whole motor, battery, and drive > mechanism revolve around a fixed shaft. ie the battery will be rotating > and > likely be left in any position. > > the battery measures 4x2x1 1/2 ins. > > Info printed on the case :- DiaMec > Non-spillable sealed Rechargeable > Battery > DM12- 1.3 (12v1.3AH/20HR) > > My question is, does Non Spillable mean that it won't leak if you tip it > over, or does it mean that it can be used and left in any position? > > Malcolm. > > _______________________________________________ > 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 From foreilly at bestweb.net Fri Jun 19 02:35:48 2009 From: foreilly at bestweb.net (Francis J. O'Reilly) Date: Thu, 18 Jun 2009 13:35:48 -0400 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <67456.29159.qm@web54507.mail.re2.yahoo.com> <1D09FD89BC994E6CB22FCA18FC630B07@R101> Message-ID: <419993A90D1442BE8F92CA631C674536@D5GHLR11> David, Didn't he do it sideways? Francis J. O'Reilly ----- Original Message ----- From: To: "Dale Eason" ; Sent: Thursday, June 18, 2009 12:50 PM Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > Thank you, Dale. > > It has not occurred to almost any amateur that one may use a SUBDIAMeTER > FLAT for autocollimation. All one needs to do is have a flat that extends > from the edge of the secondary to the edge of the primary. Please, does > anyone know about this? HAS ANYONE EVER HEARD OF HOW RITCHEY USED > SUBDIAMTER FLATS TO FIGURE THE 40"? > > D-LZ130 > > > ----- Original Message ----- > From: "Dale Eason" > To: > Sent: Wednesday, June 17, 2009 4:47 PM > Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > > > > The laser usually can be gotten for less than $10. The beam splitter is > $15. > > Web cams work fine for the analysis if the proper lens is used. Setup is > no harder than a Foucualt setup. > > I only ever made one mirror from start to finish. So I guess I'm a one > time mirror maker and I found the Bath very usefull. I called it my poor > mans large collimation flat. It was almost as easy to use during figuring > as a large auto collimation flat is and a lot cheaper. I could test the > figure once it had cooled in less than 5 minutes. > > Making and using one is about the same effort as making and using the > Foucault test. As I have said before and I still stand by that statement. > > Most atm mirror makers have a camera or web cam already that will work. > Including you Bob. Your video setup will work fine for with it. > > > > Dale Eason > > --- On Wed, 6/17/09, Bob May wrote: > >> From: Bob May >> Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer >> To: atm at atmlist.net >> Date: Wednesday, June 17, 2009, 3:51 PM >> 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 >> >> rmay at nethere.com >> http: slash /nav.to slash bobmay >> http: slash /bobmay dot astronomy.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: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: 06/18/09 > 05:53:00 > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From vladimir.galogaza1 at zg.t-com.hr Fri Jun 19 03:32:30 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Thu, 18 Jun 2009 20:32:30 +0200 Subject: [ATM] Interferometry results References: <03CA3ECBDCB74DDC931E0937BFFFE628@piv555a133b59e> <007601c9f035$4ba30e80$4d45555b@mick433caf9c95> Message-ID: Mick, The cube beam splitter http://www.surplusshed.com/pages/item/l2046d.html is excellent. (It even satisfies Bob's criterion for being "cheep" :-) The mirror http://www.surplusshed.com/pages/item/pm1013.html is also good, but I will opt for smaller. Like 12.5 mm square http://www.surplusshed.com/pages/item/pm1012.html at the same price. If you are ordering from SurplusShed why not order lens(es), or you have them already? Regards Vladimir. From vladimir.galogaza1 at zg.t-com.hr Fri Jun 19 03:44:47 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Thu, 18 Jun 2009 20:44:47 +0200 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <399241.27162.qm@web81906.mail.mud.yahoo.com><8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com><001d01c9ef8d$676b9220$819a5545@amd> <6CAFB618A94D458499E36AA9DF6BD4F0@piv555a133b59e> <2FF94E4CDB5E43ACA74994141E9F4EE3@R101> Message-ID: <91A045A7AF6248F58F979FF9193DB5CD@piv555a133b59e> >Sorry, disagree. The big discoveries (even by Hubble) were made with >mirrors >using Hartmann, Foucault, and Null testing on the stars. True, And even without mirrors, by Kepler, Galileo, Ptolemy, Bruno to mention some. Even without Foucault (test) prior to his genial discovery of the famous test. And null test a la Perkin Elmer was disgrace. Conclusion, it is not the test, it is the person using it which is to be responsible for success or blame. Efficient interferometry requires computers and programs. Even Karl-Ludwig Bath had none in 1973. Today we are happy to have all ingredients, why not use them? Hubble, Foucault or Offner will not complain. Regards Vladimir From smithersscope at yahoo.com Fri Jun 19 03:39:00 2009 From: smithersscope at yahoo.com (Dave Smith) Date: Thu, 18 Jun 2009 11:39:00 -0700 (PDT) Subject: [ATM] Tahoe anyone? Message-ID: <122281.45284.qm@web51808.mail.re2.yahoo.com> Any ATMs in the Tahoe area? I'm headed there (Incline Village) this weekend and will be taking my 16" tridob for first light with the go-to system installed. Thanks, dave From scopebuilder at gmail.com Fri Jun 19 04:17:11 2009 From: scopebuilder at gmail.com (Scope Builder) Date: Thu, 18 Jun 2009 15:17:11 -0400 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <419993A90D1442BE8F92CA631C674536@D5GHLR11> References: <67456.29159.qm@web54507.mail.re2.yahoo.com><1D09FD89BC994E6CB22FCA18FC630B07@R101> <419993A90D1442BE8F92CA631C674536@D5GHLR11> Message-ID: Francis, Just curious... Is this how you are planning to use your 7" flats? Dave ----- Original Message ----- > From: >> It has not occurred to almost any amateur that one may use a SUBDIAMeTER >> FLAT for autocollimation. All one needs to do is have a flat that extends >> from the edge of the secondary to the edge of the primary. Please, does >> anyone know about this? HAS ANYONE EVER HEARD OF HOW RITCHEY USED >> SUBDIAMTER FLATS TO FIGURE THE 40"? From vladimir.galogaza1 at zg.t-com.hr Fri Jun 19 04:45:14 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Thu, 18 Jun 2009 21:45:14 +0200 Subject: [ATM] imbeded movies Message-ID: <2DD76BE92BB644FC9C21745FC5B01346@piv555a133b59e> I will appreciate receiving help on how to include video clips into text messages. I have seen many sites with text containing images which have triangle icon (like the one for "play" ) in the middle. Clicking on triangle starts the video clip. How is this done? Regards Vladimir From rmay at nethere.com Fri Jun 19 04:56:43 2009 From: rmay at nethere.com (Bob May) Date: Thu, 18 Jun 2009 12:56:43 -0700 Subject: [ATM] Sealed Lead Battery References: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95> <04F86341EC36433BBAD5EBF507633C15@Grandad> Message-ID: <001c01c9f04e$e807a420$72ff1345@amd> I don't know the battery but it does sound like a gel cell battery and those will work just fine in any attitude. Surest way to know is to see if the battery will charge and discharge upside down. It won't hurt the battery and it will return to normal operation if it doesn't work upside down. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Fri Jun 19 05:05:24 2009 From: rmay at nethere.com (Bob May) Date: Thu, 18 Jun 2009 13:05:24 -0700 Subject: [ATM] ATM: Eric Mobsby References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk> <002901c9eea5$b8babc70$2a303550$@de> <003101c9ef8e$fa52e1a0$819a5545@amd> <27A3A4E7674A459D99F03BCBC95111A8@dittda7685d135> Message-ID: <004901c9f050$1e410f80$72ff1345@amd> Ype, you're right on the qualititive vs. quantitive!!! I'll also note that I edited the list several times and forgot the lateral wire test as well as some variations on the Foucault test like the DAFT (Diffraction Assisted Foucault Test) test I've got on my website as well as others. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From vladimir.galogaza1 at zg.t-com.hr Fri Jun 19 05:16:08 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Thu, 18 Jun 2009 22:16:08 +0200 Subject: [ATM] Interferometry results References: <03CA3ECBDCB74DDC931E0937BFFFE628@piv555a133b59e> <007601c9f035$4ba30e80$4d45555b@mick433caf9c95> <010001c9f04d$649675e0$4d45555b@mick433caf9c95> Message-ID: <05C9F1E84B58412EBA2B628FE9CFBA2F@piv555a133b59e> Mick, I was working mostly with 1mW red diode laser pointers and coated mirrors. 1mW is more than enough. But I also have 5mW green laser and it is very nice and handy to project interferogram onto the distant cardboard or wall while adjusting the whole thing, and this is easy with green 5mW laser. In such case you can work without the camera and computer and when everything is ok, just put the camera in. Regarding PCX lens I never used one, all my lenses were BCX. SurplusShed http://www.surplusshed.com/finder.cfm has on stock: L5839 diameter 5.5 mm, FL 10 mm, coated, for $ 4.00 PL1098 diameter 7.5 mm, FL 10 mm, not coated for $ 5.00 I think PCX will work but it must be proved by comparing results obtained with PCX and BCX lenses on the same mirror. Worth trying. Regards Vladimir. From rmay at nethere.com Fri Jun 19 05:11:08 2009 From: rmay at nethere.com (Bob May) Date: Thu, 18 Jun 2009 13:11:08 -0700 Subject: [ATM] imbeded movies References: <2DD76BE92BB644FC9C21745FC5B01346@piv555a133b59e> Message-ID: <006601c9f050$eb6cdd40$72ff1345@amd> The process is the same as to show a bigger image of the picture. Look on my website source on the main page and you will see how to do the basic thing. That is what I've been doing. There is also a video of a guy grinding a mirror in the plaster tool method of making a mirror but I don't remember whether it is from text or a photo. You talk of the Bath being easy to do, watch that video and you will understand why it really isn't that easy to build! Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From rmay at nethere.com Fri Jun 19 05:16:18 2009 From: rmay at nethere.com (Bob May) Date: Thu, 18 Jun 2009 13:16:18 -0700 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer References: <399241.27162.qm@web81906.mail.mud.yahoo.com><8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com> <001d01c9ef8d$676b9220$819a5545@amd> <6CAFB618A94D458499E36AA9DF6BD4F0@piv555a133b59e> Message-ID: <006901c9f051$a3f92080$72ff1345@amd> One of the things you have to remember, Vlad, is that we occasionally get requests as to how to build a Foucault tester and have seen some really "inventive" constructions of them by individuals that don't fully understand what they are doing. The Bath is a lot more difficult to understand and build than a Stellafance tester. In addition, somebody that is basically just building a telescope for the first time usually doesn't have the parts on hand like those of us that like to play with optics so they won't have any of the stuff that is needed. I get requests all of the time about what lenses of which catalog would be suitable for a camera lens. This despite the (hopefully) very simple plain instructions on my page concerning this sort of thing. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From baldjeff at comcast.net Fri Jun 19 05:19:43 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Thu, 18 Jun 2009 13:19:43 -0700 Subject: [ATM] Tahoe anyone? References: <122281.45284.qm@web51808.mail.re2.yahoo.com> Message-ID: <38B1BF4D6A864D10B0A94296E3295C1A@glendaspc> We'll be about 18 miles south of Tahoe as the crow flies at Peddler Hill, elevation 7000'. Weather forecast is excellent at this time. Bald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org ----- Original Message ----- From: "Dave Smith" To: "ATMLIST" Sent: Thursday, June 18, 2009 11:39 AM Subject: [ATM] Tahoe anyone? > Any ATMs in the Tahoe area? > I'm headed there (Incline Village) this weekend and will be taking my 16" > tridob for first light with the go-to system installed. > > Thanks, > dave > > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From chaosopher23 at yahoo.com Fri Jun 19 05:55:40 2009 From: chaosopher23 at yahoo.com (Kevin MIchael Zabbo) Date: Thu, 18 Jun 2009 13:55:40 -0700 (PDT) Subject: [ATM] silvering success Message-ID: <649599.57991.qm@web33004.mail.mud.yahoo.com> Can you get some silver nitrate reagent grade crystals? If so, you can go to the grocery store or hardware store and get distilled water, and produce as much silver nitrate compound in as high a molar concentration as you like. This is the path I will take when I silver my monster Cass. Keep us posted on that u-scope slide beam splitter, I might want to make one someday. Kevin --- On Mon, 6/1/09, Dominic-Luc Webb wrote: > From: Dominic-Luc Webb > Subject: [ATM] silvering success > To: "ATM Superheros" > Date: Monday, June 1, 2009, 11:52 AM > > I now spent some efffort on the silvering process. I used > considerably more dilute silver nitrate than described: > > http://www.atmsite.org/contrib/Coslo/silver/ > > That article apparently used pure anhydrous silver > nitrate. > Stock solution worked out to be 0.5 M. Final volume would > be 4 times more, so 0.125 M. What was available to me was > 0.1 M stock. I compensated by using very concentrated > NaOH and sugar. I heated the final mix in presence of the > microscope slides I wanted partially silvered. Goal is > 50:50 beam splitter. First effort was a bit too lightly > silvered, but expect to hit target today or tomorrow. I > will be improving the chemical preparation and then > post some details. > > First impression is that this goes for simple tasks like > making a rudimentary beam splitter. > > Dominic > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From stainless_steel at suddenlink.net Fri Jun 19 06:02:18 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 16:02:18 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <2FF94E4CDB5E43ACA74994141E9F4EE3@R101> References: <399241.27162.qm@web81906.mail.mud.yahoo.com><8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com><001d01c9ef8d$676b9220$819a5545@amd><6CAFB618A94D458499E36AA9DF6BD4F0@piv555a133b59e> <2FF94E4CDB5E43ACA74994141E9F4EE3@R101> Message-ID: <4B2172553B8D415B94C154B6E6B9BCC1@R101> Uh, that's what I said. D-LZ130 ----- 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 > > _______________________________________________ > 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 From stainless_steel at suddenlink.net Fri Jun 19 06:03:11 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 16:03:11 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <419993A90D1442BE8F92CA631C674536@D5GHLR11> References: <67456.29159.qm@web54507.mail.re2.yahoo.com> <1D09FD89BC994E6CB22FCA18FC630B07@R101> <419993A90D1442BE8F92CA631C674536@D5GHLR11> Message-ID: Yes. ----- Original Message ----- From: "Francis J. O'Reilly" To: "David Harbour" Cc: Sent: Thursday, June 18, 2009 12:35 PM Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > David, > > Didn't he do it sideways? > > Francis J. O'Reilly > ----- Original Message ----- > From: > To: "Dale Eason" ; > Sent: Thursday, June 18, 2009 12:50 PM > Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > > >> Thank you, Dale. >> >> It has not occurred to almost any amateur that one may use a SUBDIAMeTER >> FLAT for autocollimation. All one needs to do is have a flat that extends >> from the edge of the secondary to the edge of the primary. Please, does >> anyone know about this? HAS ANYONE EVER HEARD OF HOW RITCHEY USED >> SUBDIAMTER FLATS TO FIGURE THE 40"? >> >> D-LZ130 >> >> >> ----- Original Message ----- >> From: "Dale Eason" >> To: >> Sent: Wednesday, June 17, 2009 4:47 PM >> Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer >> >> >> >> The laser usually can be gotten for less than $10. The beam splitter is >> $15. >> >> Web cams work fine for the analysis if the proper lens is used. Setup is >> no harder than a Foucualt setup. >> >> I only ever made one mirror from start to finish. So I guess I'm a one >> time mirror maker and I found the Bath very usefull. I called it my poor >> mans large collimation flat. It was almost as easy to use during >> figuring >> as a large auto collimation flat is and a lot cheaper. I could test the >> figure once it had cooled in less than 5 minutes. >> >> Making and using one is about the same effort as making and using the >> Foucault test. As I have said before and I still stand by that >> statement. >> >> Most atm mirror makers have a camera or web cam already that will work. >> Including you Bob. Your video setup will work fine for with it. >> >> >> >> Dale Eason >> >> --- On Wed, 6/17/09, Bob May wrote: >> >>> From: Bob May >>> Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer >>> To: atm at atmlist.net >>> Date: Wednesday, June 17, 2009, 3:51 PM >>> 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 >>> >>> rmay at nethere.com >>> http: slash /nav.to slash bobmay >>> http: slash /bobmay dot astronomy.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: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: >> 06/18/09 >> 05:53:00 >> >> _______________________________________________ >> ATM mailing list http://www.atmlist.net/ > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: 06/18/09 05:53:00 From stainless_steel at suddenlink.net Fri Jun 19 06:05:40 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 16:05:40 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: <91A045A7AF6248F58F979FF9193DB5CD@piv555a133b59e> References: <399241.27162.qm@web81906.mail.mud.yahoo.com><8d3a545d0906161406i7499e3a9hcd964afefc982dad@mail.gmail.com><001d01c9ef8d$676b9220$819a5545@amd> <6CAFB618A94D458499E36AA9DF6BD4F0@piv555a133b59e> <2FF94E4CDB5E43ACA74994141E9F4EE3@R101> <91A045A7AF6248F58F979FF9193DB5CD@piv555a133b59e> Message-ID: Sell Stated. D-LZ130 ----- Original Message ----- From: "Vladimir Galogaza" To: Cc: "ATM List" Sent: Thursday, June 18, 2009 1:44 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, Foucault, and Null testing on the stars. > > True, > > And even without mirrors, by Kepler, Galileo, Ptolemy, Bruno to mention > some. > Even without Foucault (test) prior to his genial discovery of the famous > test. > > And null test a la Perkin Elmer was disgrace. > > Conclusion, it is not the test, it is the person using it which is to be > responsible for success or blame. > > Efficient interferometry requires computers and programs. Even Karl-Ludwig > Bath had none in 1973. > > Today we are happy to have all ingredients, why not use them? > Hubble, Foucault or Offner will not complain. > > Regards > Vladimir > > > -------------------------------------------------------------------------------- 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 From stainless_steel at suddenlink.net Fri Jun 19 06:10:35 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 16:10:35 -0500 Subject: [ATM] webcam 2d hartmann test and foucault image analyzer In-Reply-To: References: <67456.29159.qm@web54507.mail.re2.yahoo.com><1D09FD89BC994E6CB22FCA18FC630B07@R101> <419993A90D1442BE8F92CA631C674536@D5GHLR11> Message-ID: <4999CA38F10D46999830C37D1681605A@R101> They are gone, with everything else I own. At the college (Northwest Oklahoma College) they have built a dynamite solar observatory. On the door is one bronze plaque: "David Harbour Solar Observatory". On one wall inside, is a huge biography of me, complete with the only good 8 x 10 of me ever taken. That's where the mirrors went. They weere so good that they could get away with 3 reflections without any astigmatism. D-LZ130 ----- Original Message ----- From: "Scope Builder" To: "Francis J. O'Reilly" ; "David Harbour" Cc: Sent: Thursday, June 18, 2009 2:17 PM Subject: Re: [ATM] webcam 2d hartmann test and foucault image analyzer > Francis, > Just curious... Is this how you are planning to use your 7" flats? > Dave > > ----- Original Message ----- >> From: >>> It has not occurred to almost any amateur that one may use a SUBDIAMeTER >>> FLAT for autocollimation. All one needs to do is have a flat that >>> extends >>> from the edge of the secondary to the edge of the primary. Please, does >>> anyone know about this? HAS ANYONE EVER HEARD OF HOW RITCHEY USED >>> SUBDIAMTER FLATS TO FIGURE THE 40"? > -------------------------------------------------------------------------------- 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 From stainless_steel at suddenlink.net Fri Jun 19 06:12:55 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 16:12:55 -0500 Subject: [ATM] imbeded movies In-Reply-To: <2DD76BE92BB644FC9C21745FC5B01346@piv555a133b59e> References: <2DD76BE92BB644FC9C21745FC5B01346@piv555a133b59e> Message-ID: <65AF9DCCAE4B4916872F7DAF3BBD3E0C@R101> Vladimir: The message must be an html message. Not allowed on the list, but can send off list. D-LZ130 ----- Original Message ----- From: "Vladimir Galogaza" To: "ATM List" Cc: ; Sent: Thursday, June 18, 2009 2:45 PM Subject: [ATM] imbeded movies >I will appreciate receiving help on how to include video clips into text >messages. > I have seen many sites with text containing images which have triangle > icon > (like the one for "play" ) in the middle. Clicking on triangle starts the > video clip. > How is this done? > > Regards > Vladimir > _______________________________________________ > ATM mailing list http://www.atmlist.net/ -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.339 / Virus Database: 270.12.78/2185 - Release Date: 06/18/09 05:53:00 From b-hamburger at artinso.com Fri Jun 19 06:15:42 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Thu, 18 Jun 2009 23:15:42 +0200 Subject: [ATM] : Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl><20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> <20090616151934.29sfybj14w8o0g0g@mail.bbastrodesigns.com> Message-ID: <003301c9f059$f1c19100$d544b300$@com> > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Richard Schwartz > Sent: jueves, 18 de junio de 2009 17:18 > To: Nils Olof Carlin > Cc: > Subject: Re: [ATM] : Eric Mobsby > > "The human eye-brain is remarkably sensitive. Just because it can't > be measured doesn't mean that it's somehow inferior or invalid or to > be judged harshly." > > This is the basis of quack antiscience "vibrational medicine" such as > homeopathy, theraputic touch, naturopathy, accupuncture, > intercessionary prayer, aroma therapy, and ann that spooky stuff. Richard, And from someone (me) who for years has had over and over personal proof that this quack antiscience deserves neither quack nor anti, I can tell you that especially if it comes to quantifying instinctly curved surfaces, there is nothing to beat the eye. I have had ample experience in violin making where all surfaces are curved, that "exact" measuring with measuring devices would not even come close in exactness to what we call "Augenmass" in German. You will find that no experienced Violinmaker, sculptor, painter etc. will create his objects of art with the aid of rulers, compasses let alone electronic devices and yet they will display perfect proportions. I admit that we talk about very close tolerances in mirror making, but at the end of the day, the best mirrors are not made by the guy with the most advanced testing and measuring equipment, but by the artist who has, apart from experience, a distinct "feel" for what he is doing. I strongly believe that especially a not quantifiable test like the Ronchi will tell the intuitive maker all he needs to know about the glass in his hands. Berthold From stainless_steel at suddenlink.net Fri Jun 19 06:19:14 2009 From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net) Date: Thu, 18 Jun 2009 16:19:14 -0500 Subject: [ATM] A TM: Hairbrush Mirrors. Message-ID: I guess no one remembers Eric Mobsby's "Hair brush Mirrors", do they? I laid down a challenge, but no one took it up. Is everyone an amnesiac, on this list? D-LZ130 From richard1941 at gmail.com Fri Jun 19 09:01:49 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Thu, 18 Jun 2009 20:01:49 -0400 Subject: [ATM] A TM: Hairbrush Mirrors. In-Reply-To: References: Message-ID: Actually, something like a hairbrush might work with fused glass: a large number of small rods between two thin plates. I intent to try this when I get home. I know that something similar has worked for one of the other fuserz. Sent from my iPhone On Jun 18, 2009, at 17:19, wrote: > > > I guess no one remembers Eric Mobsby's "Hair brush Mirrors", do they? > > I laid down a challenge, but no one took it up. Is everyone an > amnesiac, on this list? > > D-LZ130 > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From burrjaw at earthlink.net Fri Jun 19 09:02:25 2009 From: burrjaw at earthlink.net (Jim Burrows) Date: Thu, 18 Jun 2009 17:02:25 -0700 Subject: [ATM] Q's for Mel Bartels re: Oversize pitch tool with turntable? In-Reply-To: <4A3998EE.5090802@gfphoto.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> Message-ID: At 2009-06-17 21:31 -0400, Gary Fuchs wrote: >I've been reading posts going back about twelve years (including >answers to my previous questions - thanks) and your site, and >probably missed it but was wondering if there is anything special to >know about polishing using your oversize pitch tool method with a 3 >RPM turntable? Right now it's a 9" f4.5 or so I'm getting ready to polish. This post's subject should be "Reactive Starlap". What you do is measure the mirror surface deviations before and after a starlap spell (this works very nicely on a turntable - I've been using a pottery wheel for figuring). Then you run a program that uses the three pieces of information - starlap shape, deviations before and after the spell - to calculate a new starlap shape that will get rid of the deviations assuming you use the same stroke. My experience with this is that is the calculated shape, which assumes a linear system, will quite often overshoot, so I have another program that interpolates between the two starlap shapes. -- Jim Burrows -- http://home.earthlink.net/~burrjaw -- mailto:burrjaw at earthlink.net -- Seattle N47.4723 W122.3662 (WGS84) From richard1941 at gmail.com Fri Jun 19 09:06:31 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Thu, 18 Jun 2009 20:06:31 -0400 Subject: [ATM] Ronchi Grating Question In-Reply-To: <2015F9C887DC45F39DABF13D249AE59A@dittda7685d135> References: <000f01c9ec78$3a205d40$a9fe1345@amd> <7F87286500D843538529A4E8A9ED6A6C@dittda7685d135> <2015F9C887DC45F39DABF13D249AE59A@dittda7685d135> Message-ID: For star testing use two grids with the focus between. What you see is a Moir? pattern that amplifies mirror (and grid) errors. Disclaimer: I have not yet done this! Sent from my iPhone On Jun 16, 2009, at 5:41, "Nils Olof Carlin" wrote: > Richard, > > yes, but why bother? A Ronchi grid may be helpful for detecting > zones or roughness (including a turned edge), but sweeping a > Foucault knife-edge across the field will give the same information > (and with no diffraction grating side-effects). But it is of > doubtful value for figuring. With diligence, you *can* extract zonal > information by measuring the positions of the bands, and process it > with SIXTESTS, but who does? It may show when you have polished to a > decent sphere, but "pattern-matching" by eye is bound to fail (for > an explanation, see Suiter's Star Testing...). > > A rough grid will appear "quite fuzzy" with diffuse lighting - but > even the best Ronchi bands look fuzzy, and who can tell the > difference without a good grid to compare with? > > Nils Olof > > > ----- Original Message ----- From: "Richard Schwartz" > > To: "Nils Olof Carlin" > Cc: "Bob May" ; > Sent: Tuesday, June 16, 2009 12:47 AM > Subject: Re: [ATM] Ronchi Grating Question > > >> There are two ways of ronchi testing. One way is to have a point >> source and put the grating in the light cone. The other way is to >> have an extended light source with the light passing twice through >> the grating. >> >> Sent from my iPhone >> >> On Jun 14, 2009, at 8:49, "Nils Olof Carlin" > > wrote: >> >>>> What the above actually says is that that 6 dot wide line will be >>>> extremely rough in its actual size and straightness. A Ronchi >>>> grating needs to have nice sharp straight edges to work well. >>> >>> >>> With the common method of illumination through the Ronchi grid, >>> using a fairly wide light source (such as a LED), what you see is >>> not the image of particular lines, but a composite image of many >>> lines superimposed, averaged both horizontally and vertically. By >>> averaging, the lines will look clear and straight, despite local >>> irregularities of each line (that would be revealed by using a >>> true point source of light). >>> >>> Nils Olof >>> _______________________________________________ >>> ATM mailing list http://www.atmlist.net/ > From richard1941 at gmail.com Fri Jun 19 09:35:14 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Thu, 18 Jun 2009 20:35:14 -0400 Subject: [ATM] de register In-Reply-To: References: Message-ID: Your testosterone level is too high and your skin is too thin for you to benefit from our experience. Perhaps you were frustrated by orthodox traditional methods when modern practice is much easier. Good luck to you anyway. Sent from my iPhone On Jun 17, 2009, at 2:36, "John & Joyce" wrote: > I wish to get out of the mailing list, I am not interested in chat > room talk that clogs up my email box everytime I go on line. Please > de -register me, I am no longer interested in the ATM site. John > Wall. > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Fri Jun 19 14:25:28 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Thu, 18 Jun 2009 22:25:28 -0700 Subject: [ATM] Q's for Mel Bartels re: Oversize pitch tool with turntable? In-Reply-To: <4A3998EE.5090802@gfphoto.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> Message-ID: <008201c9f09e$620b5a60$26220f20$@com> >>> I've been reading posts going back about twelve years (including answers to my previous questions - thanks) and your site, and probably missed it but was wondering if there is anything special to know about polishing using your oversize pitch tool method with a 3 RPM turntable? Right now it's a 9" f4.5 or so I'm getting ready to polish. <<< If it's a Draper/Hindle machine, which I've used up to 30 inches, then it works fine. The Elgin MOM type, I don't know, I haven't tried it. >>> You describe building up the plywood base with thin wood to form a convex surface - how carefully do you need to do that? <<< Just to help the pitch stay at roughly constant thickness from center to edge. Door skins are 3/32" thick, so that's my resolution. >>> Do you ever get any problems with moisture being released from the wood after the pitch is poured? I'm guessing not as I didn't see it mentioned and you specify high quality ply. <<< No. >>> For polishing out what stroke(s) do you use? And when you do say a 1/3W is that referenced to the center of the mirror? <<< Short strokes with just enough side swing to match edges. Mel Bartels From mbartels at bbastrodesigns.com Fri Jun 19 14:25:28 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Thu, 18 Jun 2009 22:25:28 -0700 Subject: [ATM] : Eric Mobsby In-Reply-To: References: <8A153C59EAF74BF9B0E0F7A6C43FD463@R101><0ADF4C4793994FE29190118274FBCC0D@D5GHLR11><1357820178.20090616140700@foucault.co.uk><4A37C60E.7337.00A0.0@waternet.nl><20090616133634.pd2553pecgkoo80o@mail.bbastrodesigns.com> <20090616151934.29sfybj14w8o0g0g@mail.bbastrodesigns.com> Message-ID: <008801c9f09e$67b76120$37262360$@com> >>> I would love to join one of your mirror making class, but I have of course no first-hand comments about your mirrors. BTW, just how do you match the Ronchi patterns? <<< There's always that trip to the Oregon Star Party in mid-August, half way around the world! We'd love to have you and you'd love all the home built atm stuff that shows up. AFATRT, I suppose the answer is, it's in the archives, and, very carefully. I start ~ .5 inch inside RoC and in .1 inch increments, compare until .5 inch outside RoC. I look for number of bands at various elevations across the mirror face, the degree and style of curvature, basically everything. It's best to discuss all the intricacies in person with a mirror that has problems! Mel Bartels From ncain at frontier.co.uk Fri Jun 19 18:15:34 2009 From: ncain at frontier.co.uk (Nicholas Cain) Date: Fri, 19 Jun 2009 10:15:34 +0100 Subject: [ATM] imbeded movies References: <2DD76BE92BB644FC9C21745FC5B01346@piv555a133b59e> Message-ID: <003801c9f0be$80ac2e70$510811ac@corp.frontier.co.uk> usually it's a youtube video - when you upload a video to youtube it'll give you some code you can paste into your site. There are other ways of doing it with commercial packages where you can keep the video on your own site, but why bother - using youtube means your readers use up their bandwidth instead of yours when they watch the clip (youtube's appalling image quality is perhaps one reason to hunt down alternatives) Nik ----- Original Message ----- From: "Vladimir Galogaza" To: "ATM List" Cc: ; Sent: Thursday, June 18, 2009 8:45 PM Subject: [ATM] imbeded movies >I will appreciate receiving help on how to include video clips into text >messages. > I have seen many sites with text containing images which have triangle > icon > (like the one for "play" ) in the middle. Clicking on triangle starts the > video clip. > How is this done? > > Regards > Vladimir > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From toliman at wave.co.nz Fri Jun 19 18:52:21 2009 From: toliman at wave.co.nz (Malcolm McDonald) Date: Fri, 19 Jun 2009 21:52:21 +1200 Subject: [ATM] Sealed Lead Battery References: <009a01c9ef96$84fe9720$4d45555b@mick433caf9c95><04F86341EC36433BBAD5EBF507633C15@Grandad> <001c01c9f04e$e807a420$72ff1345@amd> Message-ID: <92E2ACC4608844E58A482BB692E82B64@Grandad> Thanks for all the replies, and useful information, to my queri about Sealed Led Batteries. I have already completed the drive except for a little / lot of debugging, but when mounting the battery I realised that it would spend a lot of time upside down. I had ominous visions of all the electrolite draining off, leaving the plates sizzle up or the liquid to boil and explode, but I am now assured that all is well. Malcolm From vorblesnak at peak.org Mon Jun 22 00:37:09 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Sun, 21 Jun 2009 08:37:09 -0700 (PDT) Subject: [ATM] Some foam and glass reports Message-ID: <2424.69.59.200.230.1245598629.squirrel@webmail.peak.org> Bob reports he cannot get a figure on the blank I sent him. The glass is moving on the foam and the zones will not correct. I suspect it is the polyester foam adhesive I used to bond the glass to the glass foam. I have begun to polish the tessellated blank but I have also entered a very busy time at work and I have not been able to touch the thing for two weeks. Hopefully by the end of June I will have evenings available to polish and test. On the fused blank that I dropped .. The surfaces are still well polished and show an improving figure, but they have lost coherency across the break. It is almost like two mirrors. Does anyone want to comment on that? Could I polish in coherency? This is like the tessellated blank but done with just two pieces of glass. David David Toledo, OR 97391 From jhm.vangastel at ziggo.nl Mon Jun 22 00:42:52 2009 From: jhm.vangastel at ziggo.nl (Jan van Gastel) Date: Sun, 21 Jun 2009 17:42:52 +0200 Subject: [ATM] 20 inch f/3.6 telescope with Mike Lockwood mirror finished References: <446404.49074.qm@web54109.mail.re2.yahoo.com> Message-ID: My 20 inch f/3.6 computerized Dobsonian is finished. Information and pictures shown at http://members.ziggo.nl/jhm.vangastel/Astronomy/shorty/f3.6.htm . Jan http://members.ziggo.nl/jhm.vangastel/Astronomy/ From jeffrowe at austin.rr.com Mon Jun 22 01:52:43 2009 From: jeffrowe at austin.rr.com (Jeff Rowe) Date: Sun, 21 Jun 2009 11:52:43 -0500 Subject: [ATM] 20 inch f/3.6 telescope with Mike Lockwood mirror finished In-Reply-To: References: <446404.49074.qm@web54109.mail.re2.yahoo.com> Message-ID: <4A3E655B.2050305@austin.rr.com> Jan; Very nice!! Great work! Best JR Jan van Gastel wrote: > My 20 inch f/3.6 computerized Dobsonian is finished. Information and > pictures shown at > http://members.ziggo.nl/jhm.vangastel/Astronomy/shorty/f3.6.htm . > > Jan > http://members.ziggo.nl/jhm.vangastel/Astronomy/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From mbartels at bbastrodesigns.com Mon Jun 22 02:06:09 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Sun, 21 Jun 2009 10:06:09 -0700 Subject: [ATM] 20 inch f/3.6 telescope with Mike Lockwood mirror finished In-Reply-To: References: <446404.49074.qm@web54109.mail.re2.yahoo.com> Message-ID: <003001c9f292$9e0e3cd0$da2ab670$@com> Jan, you're getting taller all the time! Mel Bartels My 20 inch f/3.6 computerized Dobsonian is finished. Information and pictures shown at http://members.ziggo.nl/jhm.vangastel/Astronomy/shorty/f3.6.htm . Jan http://members.ziggo.nl/jhm.vangastel/Astronomy/ From b-hamburger at artinso.com Mon Jun 22 02:31:18 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Sun, 21 Jun 2009 19:31:18 +0200 Subject: [ATM] 20 inch f/3.6 telescope with Mike Lockwood mirror finished In-Reply-To: <003001c9f292$9e0e3cd0$da2ab670$@com> References: <446404.49074.qm@web54109.mail.re2.yahoo.com> <003001c9f292$9e0e3cd0$da2ab670$@com> Message-ID: <00d401c9f296$178ecae0$46ac60a0$@com> Or his telescopes are getting shorter. Next you will have to bend down (30" F2?) Berthold > -----Original Message----- > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf > Of Mel Bartels > Sent: domingo, 21 de junio de 2009 19:06 > To: atm at atmlist.net; atm_free at yahoogroups.com; bigdob at yahoogroups.com > Subject: Re: [ATM] 20 inch f/3.6 telescope with Mike Lockwood mirror > finished > > Jan, you're getting taller all the time! Mel Bartels > > > > My 20 inch f/3.6 computerized Dobsonian is finished. Information and > pictures shown at > http://members.ziggo.nl/jhm.vangastel/Astronomy/shorty/f3.6.htm . > > Jan > http://members.ziggo.nl/jhm.vangastel/Astronomy/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From tstokes at pacbell.net Mon Jun 22 14:23:36 2009 From: tstokes at pacbell.net (Tom Stokes) Date: Sun, 21 Jun 2009 22:23:36 -0700 Subject: [ATM] 20 inch f/3.6 telescope with Mike Lockwood mirror finished References: <446404.49074.qm@web54109.mail.re2.yahoo.com> Message-ID: <53B564A0FFEE41DB91846883972ECF0C@tom> Your ground ring is too short. ----- Original Message ----- From: "Jan van Gastel" To: "Mike Lockwood" ; ; ; Sent: Sunday, June 21, 2009 8:42 AM Subject: [ATM] 20 inch f/3.6 telescope with Mike Lockwood mirror finished > My 20 inch f/3.6 computerized Dobsonian is finished. Information and > pictures shown at > http://members.ziggo.nl/jhm.vangastel/Astronomy/shorty/f3.6.htm . > > Jan > http://members.ziggo.nl/jhm.vangastel/Astronomy/ > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From dlwebb at canit.se Mon Jun 22 20:57:22 2009 From: dlwebb at canit.se (Dominic-Luc Webb) Date: Mon, 22 Jun 2009 13:57:22 +0200 (MET DST) Subject: [ATM] silvering success In-Reply-To: <649599.57991.qm@web33004.mail.mud.yahoo.com> Message-ID: On Thu, 18 Jun 2009, Kevin MIchael Zabbo wrote: > Can you get some silver nitrate reagent grade crystals? It exists commercially. Sigma Aldrich carries it for instance. > > Keep us posted on that u-scope slide beam splitter, I might > want to make one someday. > > Kevin The process, much like described in my last post on this thread, essentially worked. I think the trick here is to make sure you get good yield of AgO from the nitrate solution while keeping concentration high. It is not necessary to carry out the reactions to the final deposition in same solution. This might not even be desirable. I ended up precipitating out the AgO with NaOH pellets until no further precipitate could form and solution was clear. If it is dark, Ag2+ is still in solution. It is possible to filter or pour out solution when this goes to completion. Afterwards, ammonia, like concentration found in grocery store can be used to re-suspect AgO and bring Ag into the di-amine intermediate. I then added the microscope slides with tape on one side so silvering only occured on one side. Silvering reaction was then initiated with table sugar nearly as thick as syrup as reducing agent together with a couple drops of lemon juice. Container was a small tray and this was aggitated over hot water. The above worked, but has not been as efficient as expected. There is a lot of waste in this process. Only a small amount of the silver gets on the glass. A great deal stays in solution as a black end product. Maybe Ag can be re-precipitated as AgO with NaOH, but it would require a lot. I would have to take some guesses on what the end product is, could guess some azides are present that were not there in beginning, but think these usually break down. BTW... I seem to remember stories about azides damaging pipes, so much water needed. Also, the final mix can give some deep and permanent color to porcelain. Do not do this in a sink you care about. That ugly colored solution that splatters out while working could be permanent. Dominic From jlerch1 at tampabay.rr.com Mon Jun 22 22:11:28 2009 From: jlerch1 at tampabay.rr.com (James Lerch) Date: Mon, 22 Jun 2009 09:11:28 -0400 Subject: [ATM] silvering success In-Reply-To: References: Message-ID: <4A3F8300.5060405@tampabay.rr.com> Dominic-Luc Webb wrote: > BTW... I seem to remember stories about azides damaging > pipes, so much water needed. Also, the final mix can give > some deep and permanent color to porcelain. Do not do > this in a sink you care about. That ugly colored solution > that splatters out while working could be permanent. > > Dominic > Wow, talk about flash back to long forgotten memories. Yes that brown / black stain on your counters, sink, and what not, yea, it won't ever go away. You can make it disappear for a few days by cleaning with conc. nitric acid, but sunlight will make it re-appear. It cost me a set of kitchen counters, a sink, and a few dozen years worth of "Honey Do" favors from my wife.. BTW, instead of using sugar + citric acid as you reducing agent, try using Fructose. You can find it on the health food isle as a sugar substitute, at least here in the states. I have my version of the silvering recipe here, http://lerch.no-ip.com/atm/Silver.htm Also, building a vacuum chamber and coating your parts with aluminum will probably end up cheaper in the long run. Plus having a vacuum chamber proves handy every now and then for side projects!;-) Here is a link to a video of a canopy I coated on my RC Helicopter (*Avoid this hobby, it is a massive time and money black hole, but holy crap is it fun!) http://www.youtube.com/watch?v=MSWFZ3TbcgE http://www.youtube.com/watch?v=SyfbddhTH8k http://www.youtube.com/watch?v=DCCFcvxAOVo -- Take Care, James Lerch http://www.youtube.com/user/JlerchTampa (My helicopter crash videos and stuff) http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site) http://lerch.no-ip.com/ChangFa_Gen (My 15KW generator project) " Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. " From dlwebb at canit.se Mon Jun 22 23:16:41 2009 From: dlwebb at canit.se (Dominic-Luc Webb) Date: Mon, 22 Jun 2009 16:16:41 +0200 (MET DST) Subject: [ATM] silvering success In-Reply-To: <4A3F8300.5060405@tampabay.rr.com> Message-ID: On Mon, 22 Jun 2009, James Lerch wrote: > BTW, instead of using sugar + citric acid as you reducing agent, try > using Fructose. In the end there is little chemical difference to be had between a glucose-fructose dimer and monomeic fructose. Sucrose was cheap, handy and worked. Citric acid came from lemon tree in parking lot (free). > Also, building a vacuum chamber and coating your parts with aluminum > will probably end up cheaper in the long run. And probably better overall. The vacuum chamber is long, long delayed in my case. I did some work on one actually and even have expanded my life to include a garage with a bit of space to put it. I must say, my career has really dug in deep into this project. In present case, goal is simply a 50:50 beam splitter from microscope slide in which silvering proved quite adequate and suited time requirements. Have you ever made a beam splitter from glass in vacuum chamber? Any luck polishing away aluminum to reach a 50:50 split? Dominic From mjc5 at psu.edu Mon Jun 22 23:37:03 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 22 Jun 2009 10:37:03 -0400 Subject: [ATM] Some foam and glass reports In-Reply-To: <2424.69.59.200.230.1245598629.squirrel@webmail.peak.org> References: <2424.69.59.200.230.1245598629.squirrel@webmail.peak.org> Message-ID: <0ED1B4CA-946C-43F2-BB10-9F1766A9761F@psu.edu> On Jun 21, 2009, at 11:37 AM, vorblesnak at peak.org wrote: > > On the fused blank that I dropped .. The surfaces are still well > polished > and show an improving figure, but they have lost coherency across the > break. It is almost like two mirrors. Does anyone want to comment on > that? > Could I polish in coherency? This is like the tessellated blank but > done > with just two pieces of glass. I had wanted to ask about that sort of thing. When making a flat, it is pretty hard to keep the edges flat along with th e middle. Does any of that effect show up with the tessellated mirror? But as for the repaired foam mirror, it *is* two mirrors now. > -73 de Mike N3LI - From jlerch1 at tampabay.rr.com Tue Jun 23 00:03:04 2009 From: jlerch1 at tampabay.rr.com (James Lerch) Date: Mon, 22 Jun 2009 11:03:04 -0400 Subject: [ATM] silvering success In-Reply-To: References: Message-ID: <4A3F9D28.2060301@tampabay.rr.com> Dominic-Luc Webb wrote: > Have you ever made a beam splitter from glass in vacuum > chamber? Any luck polishing away aluminum to reach a 50:50 > split? > > There is a cheat. Instead of facing the glass directly at the evaporator, turn it at an angle of incidence. I've never intentionally made a beam splitter, but I've had several items that upon examinatin I realized would make a good beam splitter or two way mirror. For instance, if your wanting to coat a microscope slide, if its face on to the emitters it will get a 100% coating. If its Edge on to the emitters it will get near zero coating. In between the two is a spot where a 50% coating can be found. The sweet spot is more the 45 degrees because of the geometry of my emitters. If the split has to be EXACTLY 50%, then it could get tricky, but if 55/45 is good enough, then no problem.. I could probably re-write my near field evaporative simulator to solve for this, but it would probably be quicker to learn it via trial and error. -- Take Care, James Lerch http://www.youtube.com/user/JlerchTampa (My helicopter crash videos and stuff) http://lerch.no-ip.com/atm (My telescope construction,testing, and coating site) http://lerch.no-ip.com/ChangFa_Gen (My 15KW generator project) " Press on: nothing in the world can take the place of perseverance. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. " From dlwebb at canit.se Tue Jun 23 01:48:11 2009 From: dlwebb at canit.se (Dominic-Luc Webb) Date: Mon, 22 Jun 2009 18:48:11 +0200 (MET DST) Subject: [ATM] silvering success In-Reply-To: <4A3F9D28.2060301@tampabay.rr.com> Message-ID: > > Have you ever made a beam splitter from glass in vacuum > > chamber? Any luck polishing away aluminum to reach a 50:50 > > split? > > > > > > If the split has to be EXACTLY 50%, then it could get tricky, but if > 55/45 is good enough, then no problem.. > > I could probably re-write my near field evaporative simulator to solve > for this, but it would probably be quicker to learn it via trial and > error. > -- > Take Care, > James Lerch No need! If exactly 50:50 is needed, it can be accomplished from polishing on your common 100% full coated pieces. Testing can be done with a spectrophotometer in transmission mode, for instance, until 50:50 split is achieved. I can't imagine this precision is needed, but plan is to do this on some triangles and glue them together to get a cube. Dominic From paul.kulyk at gmail.com Tue Jun 23 03:11:45 2009 From: paul.kulyk at gmail.com (Paul Kulyk) Date: Mon, 22 Jun 2009 12:11:45 -0600 Subject: [ATM] Cement tile tool design Message-ID: 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 From mjc5 at psu.edu Tue Jun 23 04:08:59 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Mon, 22 Jun 2009 15:08:59 -0400 Subject: [ATM] Cement tile tool design In-Reply-To: References: Message-ID: On 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? > That, Paul, is one of the great questions of the universe. I epoxy my tiles, many others put 'em right in the tool. I believe both ways work, others disagree. 8^) -73 de Mike N3LI - From paul.kulyk at gmail.com Tue Jun 23 04:25:23 2009 From: paul.kulyk at gmail.com (Paul Kulyk) Date: Mon, 22 Jun 2009 13:25:23 -0600 Subject: [ATM] Cement tile tool design In-Reply-To: References: Message-ID: Thanks Mike. I should ask more specifically though. Is there any problem with doing something Bob May-style (http://bobmay.astronomy.net/mirrormaking/mkplaster.htm) with portland cement (no sand)? Has any one tried it? -- Paul On Mon, Jun 22, 2009 at 1:08 PM, Michael Coslo wrote: > > On 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? >> > > > That, Paul, is one of the great questions of the universe. I epoxy my tiles, > many others put 'em right in the tool. I believe both ways work, others > disagree. ?8^) > > > -73 de Mike N3LI - > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From jeffrowe at austin.rr.com Tue Jun 23 05:48:15 2009 From: jeffrowe at austin.rr.com (Jeff Rowe) Date: Mon, 22 Jun 2009 15:48:15 -0500 Subject: [ATM] silvering success In-Reply-To: References: Message-ID: <4A3FEE0F.7050702@austin.rr.com> Dominic-Luc; I imagine a great deal of precision will be required to make "adequate" triangles, (How out of true, can they be?). Could be wrong, what is the precision required in an off the shelf beam splitter? Just a thought. Best JR > >No need! If exactly 50:50 is needed, it can be accomplished >from polishing on your common 100% full coated pieces. >Testing can be done with a spectrophotometer in transmission >mode, for instance, until 50:50 split is achieved. I can't >imagine this precision is needed, but plan is to do this >on some triangles and glue them together to get a cube. > >Dominic > >_______________________________________________ >ATM mailing list http://www.atmlist.net/ > > > From alaskawolfjoe at hotmail.com Tue Jun 23 05:52:28 2009 From: alaskawolfjoe at hotmail.com (lance clarke) Date: Mon, 22 Jun 2009 16:52:28 -0400 Subject: [ATM] Cement tile tool design In-Reply-To: References: Message-ID: There is no concensus! I've done it both ways, and they both work well. When I epoxied the tiles on, I also epoxied the whole tool. When I made a tile tool directly on the tiles, it worked well too. In the end, I like both methods. Directly on the tiles is a bit faster. Lance > Date: Mon, 22 Jun 2009 12:11:45 -0600 > From: paul.kulyk at gmail.com > To: atm at atmlist.net > Subject: [ATM] Cement tile tool design > > 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/ _________________________________________________________________ Internet explorer 8 lets you browse the web faster. http://go.microsoft.com/?linkid=9655582 From rmay at nethere.com Tue Jun 23 06:03:26 2009 From: rmay at nethere.com (Bob May) Date: Mon, 22 Jun 2009 14:03:26 -0700 Subject: [ATM] Cement tile tool design References: Message-ID: <005301c9f37c$e3b42ca0$2a995545@amd> Peter DeBaan has done several cement tools and they have all worked well. Needless to say, he did them my way. The only problem that I've seen with cement is that it is sssoooo slow! I like to get my grinding under way quickly and usually don't wait long enough for the tool to fullly cure before grinding with the ol' 80 grit. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From b-hamburger at artinso.com Tue Jun 23 06:08:09 2009 From: b-hamburger at artinso.com (Berthold Hamburger) Date: Mon, 22 Jun 2009 23:08:09 +0200 Subject: [ATM] Cement tile tool design In-Reply-To: <005301c9f37c$e3b42ca0$2a995545@amd> References: <005301c9f37c$e3b42ca0$2a995545@amd> Message-ID: <013c01c9f37d$92e8ed50$b8bac7f0$@com> I have done both and would give preference to the direct pouring method for simplicity and speed. However, I make my tools with dental stone for the same reasons. Berthold -- Berthold Hamburger - Cellist/Spain Email: behambu at artinso.com http://www.artinso.com http://www.astro.artinso.com From baldjeff at comcast.net Tue Jun 23 06:21:16 2009 From: baldjeff at comcast.net (Jeff Baldwin) Date: Mon, 22 Jun 2009 14:21:16 -0700 Subject: [ATM] Cement tile tool design References: Message-ID: <11A7E73FC71346DCABD41574DB808A6E@glendaspc> Hey Paul: I am currently grinding my 24" f/3.6 with a 140# concrete tool. After casting the concrete to the mirror I thin-set the tiles onto the concrete. Afterwards I polyurethaned between the tiles and on the sides and back of the concretre to seal everything. I have done this numerous times and have experienced 1 failure in adhesion. That tile was easily replaced, but I could have just left it off and sealed the empty spot with urethane. So far this one is working perfectly. Bald Jeff and Glenda Baldwin Lathrop, CA www.stocktonastro.org >I am considering making a cement tile tool. What is the general > consensus on pouring the cement directly onto the tiles? Is it a > better idea to epoxy them on top of a hardened disk? > > Thanks, > Paul From richard1941 at gmail.com Tue Jun 23 08:54:52 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Mon, 22 Jun 2009 19:54:52 -0400 Subject: [ATM] need contact In-Reply-To: <005301c9f37c$e3b42ca0$2a995545@amd> References: <005301c9f37c$e3b42ca0$2a995545@amd> Message-ID: <5C853C5E-130E-4471-8271-311980293A96@gmail.com> I am trying to contact Gary Fuchs, as we are camping near him and would like to visit tomorrow. Can somebody please send his phone number to me off-list? Sent from my iPhone On Jun 22, 2009, at 17:03, "Bob May" wrote: > Peter DeBaan has done several cement tools and they have all > worked well. Needless to say, he did them my way. The only > problem that I've seen with cement is that it is sssoooo slow! I > like to get my grinding under way quickly and usually don't wait > long enough for the tool to fullly cure before grinding with the > ol' 80 grit. > Bob May > > rmay at nethere.com > http: slash /nav.to slash bobmay > http: slash /bobmay dot astronomy.net > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From gary at gfphoto.com Tue Jun 23 11:48:31 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Mon, 22 Jun 2009 22:48:31 -0400 Subject: [ATM] Q's for Mel Bartels re: Oversize pitch tool with turntable? In-Reply-To: <008201c9f09e$620b5a60$26220f20$@com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <008201c9f09e$620b5a60$26220f20$@com> Message-ID: <4A40427F.3010709@gfphoto.com> Thanks Mel, "If it's a Draper/Hindle machine" Just a plain 3 RPM turntable. (Could go faster but is set for 3) And a fixed post for the tool, or hand work. "Short strokes with just enough side swing to match edges. " So the mirror edge just touches the tool edge? Gary Fuchs Mel Bartels wrote: > I've been reading posts going back about twelve years (including answers > to my previous questions - thanks) and your site, and probably missed it > but was wondering if there is anything special to know about polishing > using your oversize pitch tool method with a 3 RPM turntable? Right now > it's a 9" f4.5 or so I'm getting ready to polish. > <<< > > > If it's a Draper/Hindle machine, which I've used up to 30 inches, then it > works fine. The Elgin MOM type, I don't know, I haven't tried it. > > > > You describe building up the plywood base with thin wood to form a > convex surface - how carefully do you need to do that? > <<< > > Just to help the pitch stay at roughly constant thickness from center to > edge. Door skins are 3/32" thick, so that's my resolution. > > > > Do you ever get any problems with moisture being released from the wood > after the pitch > is poured? I'm guessing not as I didn't see it mentioned and you specify > high quality ply. > <<< > > No. > > > For polishing out what stroke(s) do you use? And when you do say a 1/3W > is that referenced to the center of the mirror? > <<< > > Short strokes with just enough side swing to match edges. > > Mel Bartels > > > From gary at gfphoto.com Tue Jun 23 11:50:28 2009 From: gary at gfphoto.com (Gary Fuchs) Date: Mon, 22 Jun 2009 22:50:28 -0400 Subject: [ATM] Q's for Mel Bartels re: Oversize pitch tool with turntable? In-Reply-To: References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> Message-ID: <4A4042F4.60100@gfphoto.com> (Sorry Jim, I meant to send this to the list.) Jim, I'm not sure if you mean your post in reply to mine. In any case, could you explain more? Thanks, Gary Jim Burrows wrote: >
At > 2009-06-17 21:31 -0400, Gary Fuchs wrote: > >> I've been reading posts going back about twelve years (including >> answers to my previous questions - thanks) and your site, and >> probably missed it but was wondering if there is anything special to >> know about polishing using your oversize pitch tool method with a 3 >> RPM turntable? Right now it's a 9" f4.5 or so I'm getting ready to >> polish. > > This post's subject should be "Reactive Starlap". What you do is > measure the mirror surface deviations before and after a starlap spell > (this works very nicely on a turntable - I've been using a pottery > wheel for figuring). Then you run a program that uses the three > pieces of information - starlap shape, deviations before and after the > spell - to calculate a new starlap shape that will get rid of the > deviations assuming you use the same stroke. > > My experience with this is that is the calculated shape, which assumes > a linear system, will quite often overshoot, so I have another program > that interpolates between the two starlap shapes. > > -- Jim Burrows > -- http://home.earthlink.net/~burrjaw > -- mailto:burrjaw at earthlink.net > -- Seattle N47.4723 W122.3662 (WGS84) > > >
> From vorblesnak at peak.org Tue Jun 23 12:29:21 2009 From: vorblesnak at peak.org (vorblesnak at peak.org) Date: Mon, 22 Jun 2009 20:29:21 -0700 (PDT) Subject: [ATM] Tessellated polish, a picture Message-ID: <4014.69.59.200.230.1245727761.squirrel@webmail.peak.org> I have about three hours into the polish. It gives a good clean solar disk, I can see some detail of my face and shirt when I stand with the sun shining on me, but this is weird .. http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/Tessellated%20Polish.JPG Other than the fact that I cannot hold a camera steady. In general it is polishing more or less routinely, center out. But the middle of the hexes .. On the bigger picture in one of the upper left hexes you can just see two lines from the ronchi tester. I don't think I will see one continuous ronchi pattern. I think each hex will have it's own. David Davis Toledo, OR 97391 From atmpob at yahoo.com Tue Jun 23 14:33:05 2009 From: atmpob at yahoo.com (Dale Eason) Date: Mon, 22 Jun 2009 22:33:05 -0700 (PDT) Subject: [ATM] Tessellated polish, a picture Message-ID: <884354.28678.qm@web54501.mail.re2.yahoo.com> Cool. Maybe we can use it to simulate how a fly sees stars. This is pure speculation on my part. Could it be similar to the twyman effect. Where stress is releaved by polishing. In this case the fronts and backs have different stress. Since the back of each hex is not anchored to its neighbors then each hex is warping in a more or less spherical shape. That is the edges are either rising or falling slightly compared to the middle of each hex. Dale Eason --- On Mon, 6/22/09, vorblesnak at peak.org wrote: > From: vorblesnak at peak.org > Subject: [ATM] Tessellated polish, a picture > To: atm at atmlist.net > Date: Monday, June 22, 2009, 10:29 PM > I have about three hours into the > polish. It gives a good clean solar > disk, I can see some detail of my face and shirt when I > stand with the sun > shining on me, but this is weird .. > > http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/Tessellated%20Polish.JPG > > Other than the fact that I cannot hold a camera steady. In > general it is > polishing more or less routinely, center out. But the > middle of the hexes > .. > > On the bigger picture in one of the upper left hexes you > can just see two > lines from the ronchi tester. I don't think I will see one > continuous > ronchi pattern. I think each hex will have it's own. > > David Davis > Toledo, OR 97391 > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From dlwebb at canit.se Tue Jun 23 19:05:12 2009 From: dlwebb at canit.se (Dominic-Luc Webb) Date: Tue, 23 Jun 2009 12:05:12 +0200 (MET DST) Subject: [ATM] silvering success In-Reply-To: <4A3FEE0F.7050702@austin.rr.com> Message-ID: On Mon, 22 Jun 2009, Jeff Rowe wrote: > Dominic-Luc; > I imagine a great deal of precision will be required to make "adequate" > triangles, (How out of true, can they be?). Could be wrong, what is the > precision required in an off the shelf beam splitter? Just a thought. > Best > JR > > >mode, for instance, until 50:50 split is achieved. I can't > >imagine this precision is needed, but plan is to do this > >on some triangles and glue them together to get a cube. > > > >Dominic For clarity, precision in % transmission (e.g., 50:50 vs 49.5:50.5, etc) for the silvering of the microscope slide is issue I brought up. Precision in angles and flatness of sides of two triangles (that you bring up) to get a cube is separate issue. I assume precision of those parameters to be critical, but do-able with manual ATM labor. I'm still learning myself. Silvering was first step and this was sucessful. I do not have much info on making the triangles, so feel free to offer suggestions/references. I have my own simplistic ideas about making and testing. I have heard of a trick of grinding both pieces against a thick iron beam with a 90 degree angle. Dominic From vladimir.galogaza1 at zg.t-com.hr Tue Jun 23 20:51:56 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Tue, 23 Jun 2009 13:51:56 +0200 Subject: [ATM] silvering success References: Message-ID: It was suggested to polish aluminum coating in order to get specified transmission (split ratio), for example 50:50. my experience with aluminum coating is such that I doubt that such procedure is possible. Unprotected Al is so soft that controlled uniform removal without scratches of uncontrolled transmission are difficult to imagine. Protected Al (with SiO) is different problem. SiO will protect Al from contact with polishing agent until SiO is not removed, and then we have case 1, unprotected Al. Since this is a pure speculation from me, based on experienc in handling (cleaning) coated and uncoated mirrors (not polishing), I would like to know if anybody attempted this polishing procedure and what was the result. Regards Vladimir. From mjc5 at psu.edu Tue Jun 23 21:12:17 2009 From: mjc5 at psu.edu (Michael Coslo) Date: Tue, 23 Jun 2009 08:12:17 -0400 Subject: [ATM] silvering success In-Reply-To: References: Message-ID: <1ECFB888-9475-4A9E-8B08-E1F766CD922E@psu.edu> On Jun 23, 2009, at 7:51 AM, Vladimir Galogaza wrote: > It was suggested to polish aluminum coating in order to get > specified transmission (split ratio), for example 50:50. > > my experience with aluminum coating is such that I doubt that > such procedure is possible. I have polished off the Al coating on a mirror before. If you don't have an overcoating, if you have perfect contact from the start, and if you have exquisite control over your technique, coupled with a good bit of luck.... 8^) I wasn't trying for just taking enough Al off to affect light reflection/transmission, but the coating did not come off evenly. I'd be more inclined to think that the way to get an Al coating with a degree of transparency, would be to work at getting the coating process under good control, and get the glass coming out of the chamber at the proper transmission/reflection ratio from the start. -73 de Mike N3LI - From s.c.koehler at gmail.com Tue Jun 23 22:41:14 2009 From: s.c.koehler at gmail.com (Stephen Koehler) Date: Tue, 23 Jun 2009 08:41:14 -0500 Subject: [ATM] Tessellated polish, a picture In-Reply-To: <4014.69.59.200.230.1245727761.squirrel@webmail.peak.org> References: <4014.69.59.200.230.1245727761.squirrel@webmail.peak.org> Message-ID: <8d3a545d0906230641n93b951yb24885becae522cf@mail.gmail.com> David, On the bigger picture in one of the upper left hexes you can just see two > lines from the ronchi tester. I don't think I will see one continuous > ronchi pattern. I think each hex will have it's own. You had better see one ronchi pattern that spans all the hexes, or it won't function very well as a telescope mirror. In particular, the Ronchi pattern needs to transition smoothly across all the boundaries, or you will have the equivalent of many huge "zones" all over your mirror. If you want a mirror that performs at all well, it needs to have no worse than about 1/4 P-V error over the entire surface. Having 1/4 wave P-V error on each individual hex isn't sufficient. -- Steve Koehler From burrjaw at earthlink.net Wed Jun 24 08:42:06 2009 From: burrjaw at earthlink.net (Jim Burrows) Date: Tue, 23 Jun 2009 16:42:06 -0700 Subject: [ATM] Starlaps (was Re: Q's for Mel Bartels re: Oversize pitch tool with turntable?) In-Reply-To: <4A4042F4.60100@gfphoto.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <4A4042F4.60100@gfphoto.com> Message-ID: At 2009-06-22 22:50 -0400, Gary Fuchs wrote: >I'm not sure if you mean your post in reply to mine. In any case, could >you explain more? Tex, p. 94, sez, "If we deliberately inactivate a portion of the polishing lap,... we alter the action on the mirror correspondingly." Further on he says, "...the results are quite unpredictable; it is difficult to control fully the effect produced...". I call the deformed lap a "starlap", and what I've done is to quantify the action. To get a first look at starlap design, download http://home.earthlink.net/~burrjaw/public/starlap.zip (Win32, 2004-01-18, 243 kb) I'll repeat the former post which talks about further improvements in starlap design: >This post's subject should be "Reactive Starlap". What you do is >measure the mirror surface deviations before and after a starlap >spell (this works very nicely on a turntable - I've been using a >pottery wheel for figuring). Then you run a program that uses the >three pieces of information - starlap shape, deviations before and >after the spell - to calculate a new starlap shape that will get rid >of the deviations assuming you use the same stroke. -- Jim Burrows -- http://home.earthlink.net/~burrjaw -- mailto:burrjaw at earthlink.net -- Seattle N47.4723 W122.3662 (WGS84) From mbartels at bbastrodesigns.com Wed Jun 24 10:08:16 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Tue, 23 Jun 2009 18:08:16 -0700 Subject: [ATM] Starlaps (was Re: Q's for Mel Bartels re: Oversize pitch tool with turntable?) In-Reply-To: References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <4A4042F4.60100@gfphoto.com> Message-ID: <006901c9f468$47ccccb0$d7666610$@com> >>> Tex, p. 94, sez, "If we deliberately inactivate a portion of the polishing lap,... we alter the action on the mirror correspondingly." Further on he says, "...the results are quite unpredictable; it is difficult to control fully the effect produced...". I call the deformed lap a "starlap", and what I've done is to quantify the action. To get a first look at starlap design, download <<< I've gotten pretty good at predicting the effects. I parabolized my most recent mirror, a 13 inch f/3.0 twelve times, most of those using various types of deformed laps. I kept the stroke constant but varied the lap in order to control the figure. It's a combination of area-pressure and edge-sweeps. Mel Bartels From mbartels at bbastrodesigns.com Wed Jun 24 12:03:48 2009 From: mbartels at bbastrodesigns.com (Mel Bartels) Date: Tue, 23 Jun 2009 20:03:48 -0700 Subject: [ATM] Q's for Mel Bartels re: Oversize pitch tool with turntable? In-Reply-To: <4A40427F.3010709@gfphoto.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <008201c9f09e$620b5a60$26220f20$@com> <4A40427F.3010709@gfphoto.com> Message-ID: <007c01c9f478$6b3184b0$41948e10$@com> On the side to side swing, yes. That way the mirror goes from lap edge to lap edge when the lap is oversized. Mel Bartels -----Original Message----- From: Gary Fuchs [mailto:gary at gfphoto.com] Sent: Monday, June 22, 2009 7:49 PM To: Mel Bartels; 'ATM list' Subject: Re: Re: [ATM] Q's for Mel Bartels re: Oversize pitch tool with turntable? Thanks Mel, "If it's a Draper/Hindle machine" Just a plain 3 RPM turntable. (Could go faster but is set for 3) And a fixed post for the tool, or hand work. "Short strokes with just enough side swing to match edges. " So the mirror edge just touches the tool edge? Gary Fuchs Mel Bartels wrote: > I've been reading posts going back about twelve years (including answers > to my previous questions - thanks) and your site, and probably missed it > but was wondering if there is anything special to know about polishing > using your oversize pitch tool method with a 3 RPM turntable? Right now > it's a 9" f4.5 or so I'm getting ready to polish. > <<< > > > If it's a Draper/Hindle machine, which I've used up to 30 inches, then it > works fine. The Elgin MOM type, I don't know, I haven't tried it. > > > > You describe building up the plywood base with thin wood to form a > convex surface - how carefully do you need to do that? > <<< > > Just to help the pitch stay at roughly constant thickness from center to > edge. Door skins are 3/32" thick, so that's my resolution. > > > > Do you ever get any problems with moisture being released from the wood > after the pitch > is poured? I'm guessing not as I didn't see it mentioned and you specify > high quality ply. > <<< > > No. > > > For polishing out what stroke(s) do you use? And when you do say a 1/3W > is that referenced to the center of the mirror? > <<< > > Short strokes with just enough side swing to match edges. > > Mel Bartels > > > From vladimir.galogaza1 at zg.t-com.hr Wed Jun 24 18:37:37 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Wed, 24 Jun 2009 11:37:37 +0200 Subject: [ATM] Starlaps (was Re: Q's for Mel Bartels re: Oversize pitchtool with turntable?) References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <4A4042F4.60100@gfphoto.com> <006901c9f468$47ccccb0$d7666610$@com> Message-ID: Jim wrote: > Then you run a program that uses the >three pieces of information - starlap shape, deviations before and >after the spell - to calculate a new starlap shape that will get rid >of the deviations assuming you use the same stroke. And Mel responds with: >I've gotten pretty good at predicting the effects. I parabolized my most >recent mirror, a 13 inch f/3.0 twelve times, most of those using various >types of deformed laps. I kept the stroke constant but varied the lap in >order to control the figure. >It's a combination of area-pressure and edge-sweeps. An Excellent example of how the ATM action, based on usage of extraordinary amount of talent, experience and intuition, can be replaced by usage of a program based on understanding of the mechanism of the underlying process and thus making usage of potent procedures (starlaps, as in this example), available to every, even novice, ATM. Regards Vladimir. From fabio_falchi at yahoo.it Wed Jun 24 19:26:25 2009 From: fabio_falchi at yahoo.it (Fabio Falchi) Date: Wed, 24 Jun 2009 12:26:25 +0200 Subject: [ATM] heat and motors In-Reply-To: References: Message-ID: <5C97DEAF94C045ACB6C7CBCBF8356EAA@PCStudio> In the process of designing my altaz 80 cm dobson, I'm wondering if the goto and tracking motors will produce heat and, consequently, raising air currents. If we need to keep the mirror temperature as close as possible to the ambient one, then we cannot produce air currents with motors that are under the open frame mirror box. Any feedback? Best, Fabio Falchi From richard1941 at gmail.com Thu Jun 25 02:17:17 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Wed, 24 Jun 2009 13:17:17 -0400 Subject: [ATM] Starlaps (was Re: Q's for Mel Bartels re: Oversize pitch tool with turntable?) In-Reply-To: <006901c9f468$47ccccb0$d7666610$@com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <4A4042F4.60100@gfphoto.com> <006901c9f468$47ccccb0$d7666610$@com> Message-ID: <5A9E8CFF-4B75-48F5-9A42-3DC7ED9AC7B9@gmail.com> It Berry or Tex says it, it must be true and Mel must be a fraud an a liar. Unless... Sent from my iPhone On Jun 23, 2009, at 21:08, "Mel Bartels" wrote: >>>> > Tex, p. 94, sez, "If we deliberately inactivate a portion of the > polishing lap,... we alter the action on the mirror > correspondingly." Further on he says, "...the results are quite > unpredictable; it is difficult to control fully the effect > produced...". I call the deformed lap a "starlap", and what I've > done is to quantify the action. To get a first look at starlap > design, download > <<< > > > I've gotten pretty good at predicting the effects. I parabolized my > most > recent mirror, a 13 inch f/3.0 twelve times, most of those using > various > types of deformed laps. I kept the stroke constant but varied the > lap in > order to control the figure. > > It's a combination of area-pressure and edge-sweeps. > > Mel Bartels > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From mbartels at bbastrodesigns.com Thu Jun 25 03:46:42 2009 From: mbartels at bbastrodesigns.com (mbartels at bbastrodesigns.com) Date: Wed, 24 Jun 2009 12:46:42 -0600 Subject: [ATM] Starlaps (was Re: Q's for Mel Bartels re: Oversize pitchtool with turntable?) In-Reply-To: References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <4A4042F4.60100@gfphoto.com> <006901c9f468$47ccccb0$d7666610$@com> Message-ID: <20090624124642.t8n097duwwok0w4w@mail.bbastrodesigns.com> My point is that, as advanced and significant that Jim Burrows' software application that dimensions the deformed lap is, it unfortunately was not predictive enough for me. So I went back to the basic question, which is, "Can one predict the effect of deformed laps?". The answer is effectively yes, at least in my one example. BTW, even the Mirror Lab complains that predicting figure changes based on the lap and stroke is difficult. Mel Bartels Quoting Vladimir Galogaza : > Jim wrote: >> Then you run a program that uses the three pieces of information - >> starlap shape, deviations before and after the spell - to calculate >> a new starlap shape that will get rid of the deviations assuming >> you use the same stroke. > > And Mel responds with: >> I've gotten pretty good at predicting the effects. I parabolized my most >> recent mirror, a 13 inch f/3.0 twelve times, most of those using various >> types of deformed laps. I kept the stroke constant but varied the lap in >> order to control the figure. >> It's a combination of area-pressure and edge-sweeps. > > An Excellent example of how the ATM action, based on usage of > extraordinary amount of talent, experience and intuition, can be > replaced by usage of a program based on understanding of the mechanism > of the underlying process and thus making > usage of potent procedures (starlaps, as in this example), available to > every, even novice, ATM. > > Regards > Vladimir. > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From rmay at nethere.com Thu Jun 25 05:40:57 2009 From: rmay at nethere.com (Bob May) Date: Wed, 24 Jun 2009 13:40:57 -0700 Subject: [ATM] heat and motors References: <5C97DEAF94C045ACB6C7CBCBF8356EAA@PCStudio> Message-ID: <002a01c9f50c$163737e0$47fe1345@amd> The motors won't be under the optical path so there should be no real problem with heat rising. In any case, a shroud over the rods holding the upper cange will help in keeping any heat flows as well as light out of the optical path. Remember that the elevation motor is going to be on one side of the system and the azimuth motor can be put at the back side of the box. Bob May rmay at nethere.com http: slash /nav.to slash bobmay http: slash /bobmay dot astronomy.net From toolontop at yahoo.com Fri Jun 26 02:44:24 2009 From: toolontop at yahoo.com (Mark Cowan) Date: Thu, 25 Jun 2009 10:44:24 -0700 (PDT) Subject: [ATM] Tessellated polish, a picture Message-ID: <683815.13915.qm@web112416.mail.gq1.yahoo.com> Hi David, Say, what are we looking at here, in terms of scale? And what is the construction? Sorry if I missed this before, but what you're showing here looks like beaucoup print through to me. If the edges are free in each section, what are you using for support for the assembly? Best, Mark --- On Mon, 6/22/09, vorblesnak at peak.org wrote: > From: vorblesnak at peak.org > Subject: [ATM] Tessellated polish, a picture > To: atm at atmlist.net > Date: Monday, June 22, 2009, 8:29 PM > I have about three hours into the > polish. It gives a good clean solar > disk, I can see some detail of my face and shirt when I > stand with the sun > shining on me, but this is weird .. > > http://www.atmlist.net/contrib/vorblesnak-at-peak-dot-org/Tessellated%20Blank/Tessellated%20Polish.JPG > > Other than the fact that I cannot hold a camera steady. In > general it is > polishing more or less routinely, center out. But the > middle of the hexes > .. > > On the bigger picture in one of the upper left hexes you > can just see two > lines from the ronchi tester. I don't think I will see one > continuous > ronchi pattern. I think each hex will have it's own. > > David Davis > Toledo, OR 97391 > > > > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From burrjaw at earthlink.net Fri Jun 26 08:48:14 2009 From: burrjaw at earthlink.net (Jim Burrows) Date: Thu, 25 Jun 2009 16:48:14 -0700 Subject: [ATM] Starlaps (was Re: Q's for Mel Bartels Oversize pitchtool with turntable?) In-Reply-To: <20090624124642.t8n097duwwok0w4w@mail.bbastrodesigns.com> References: <8CBBCB72C00E96E-884-1317@webmail-me03.sysops.aol.com> <1D11C9A894B348F9BA87F91996B7F7EA@R101> <003b01c9eec0$4b5baac0$5d9a5545@amd> <280961FF-56B4-4DEC-B04A-A7BA74D58F4C@gmail.com> <001201c9eef4$272ef6f0$758ce4d0$@com> <4A3998EE.5090802@gfphoto.com> <4A4042F4.60100@gfphoto.com> <006901c9f468$47ccccb0$d7666610$@com> <20090624124642.t8n097duwwok0w4w@mail.bbastrodesigns.com> Message-ID: At 2009-06-24 12:46 -0600, Mel wrote: >My point is that, as advanced and significant that Jim Burrows' >software application that dimensions the deformed lap is, it >unfortunately was not predictive enough for me. > >So I went back to the basic question, which is, "Can one predict the >effect of deformed laps?". The answer is effectively yes, at least in >my one example. > >BTW, even the Mirror Lab complains that predicting figure changes >based on the lap and stroke is difficult. I agree. The original starlap (starlap.zip) computation assumed a specific stroke (full lap, 1/3 stroke, even pressure). There's a LOT more variables to quantify the action (temperature, lap hardness, turntable, etc., etc.) - that's why I wrote a follow-up program to use the information about what happened with a particular lap and stroke to calculate what lap have the desired effect assuming the same stroke. I haven't zipped up the program yet - sounds like maybe I'm getting enough interest to proceed... -- Jim Burrows -- http://home.earthlink.net/~burrjaw -- mailto:burrjaw at earthlink.net -- Seattle N47.4723 W122.3662 (WGS84) From dragmila at eunet.yu Fri Jun 26 12:39:14 2009 From: dragmila at eunet.yu (Dragan Miladinovic) Date: Fri, 26 Jun 2009 05:39:14 +0200 Subject: [ATM] appeal for support Message-ID: <002801c9f60f$d35b7b20$780df0d5@Miladinovic> Hi all, First I would like to apologize, for this off topic issue, but we are in a serious need of help. Due to the economic crisis, government of Serbia plans to stop provision of funds for Petnica, the largest science education institution for gifted children in Eastern Europe. Without that money, Petnica is judged to death. Astronomy is one of the most interesting fields of expertise of Petnica, and a lot of Petnica's participants were ATM'ers too.We need your help, ATM'ers, astronomy societies are welcome.Please join the petition to stop Petnica's end. More information are available at www.savepetnica.com From richard1941 at gmail.com Fri Jun 26 21:20:33 2009 From: richard1941 at gmail.com (Richard Schwartz) Date: Fri, 26 Jun 2009 08:20:33 -0400 Subject: [ATM] Richard's Travels In-Reply-To: <002801c9f60f$d35b7b20$780df0d5@Miladinovic> References: <002801c9f60f$d35b7b20$780df0d5@Miladinovic> Message-ID: <43AE0A0C-6FFC-438A-AA67-E8D8AA605EE1@gmail.com> I am in Washington DC today. If any telescope makers would like to get together, please e-mail me. Richard (from California) Sent from my iPhone On Jun 25, 2009, at 23:39, "Dragan Miladinovic" wrote: > Hi all, > First I would like to apologize, for this off topic issue, but we > are in a serious need of help. Due to the economic crisis, > government of Serbia plans to stop provision of funds for Petnica, > the largest science education institution for gifted children in > Eastern Europe. Without that money, Petnica is judged to death. > Astronomy is one of the most interesting fields of expertise of > Petnica, and a lot of Petnica's participants were ATM'ers too.We > need your help, ATM'ers, astronomy societies are welcome.Please join > the petition to stop Petnica's end. More information are available > at www.savepetnica.com > _______________________________________________ > ATM mailing list http://www.atmlist.net/ From gfbrandenburg at yahoo.com Fri Jun 26 23:06:46 2009 From: gfbrandenburg at yahoo.com (Guy Brandenburg) Date: Fri, 26 Jun 2009 07:06:46 -0700 (PDT) Subject: [ATM] Richard's Travels Message-ID: <299008.58224.qm@web111514.mail.gq1.yahoo.com> Richard, Every Friday night we have a telescope-making workshop at the Chevy Chase Community Center in northwest DC, at the intersection of McKinley Street and Connecticut Avenue, about 2 blocks from the Maryland Line (Western Avenue), from about 7 pm to 10 pm. Please do drop by tonight! 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, 6/26/09, Richard Schwartz wrote: > From: Richard Schwartz > Subject: [ATM] Richard's Travels > To: "Dragan Miladinovic" > Cc: "" > Date: Friday, June 26, 2009, 8:20 AM > I am in Washington DC today.? If > any telescope makers would like to get together, please > e-mail me. > > Richard (from California) > > Sent from my iPhone > > On Jun 25, 2009, at 23:39, "Dragan Miladinovic" > wrote: > > > Hi all, > > First I would like to apologize, for this off topic > issue, but we are in a serious need of? help. Due to > the economic crisis, government of Serbia plans to stop > provision of funds for Petnica, the largest science > education institution for gifted children in Eastern Europe. > Without that money, Petnica is judged to death. > > Astronomy is one of the most interesting fields of > expertise of Petnica, and a lot of Petnica's participants > were ATM'ers too.We need your help, ATM'ers, astronomy > societies are welcome.Please join the petition to stop > Petnica's end. More information are available at > www.savepetnica.com > > _______________________________________________ > > ATM mailing list http://www.atmlist.net/ > _______________________________________________ > ATM mailing list http://www.atmlist.net/ > From vladimir.galogaza1 at zg.t-com.hr Sat Jun 27 00:08:34 2009 From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza) Date: Fri, 26 Jun 2009 17:08:34 +0200 Subject: [A