From dlwebb at canit.se  Wed Apr  1 02:52:16 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Tue, 31 Mar 2009 19:52:16 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
Message-ID: <Pine.LNX.4.44.0903311941220.12291-100000@uno.canit.se>


Hoping someone can tell me what this tile tool material is.

I got it in California, USA years ago (Chabot) together
with the primary mirror glass I will use for my current
Mak-Cass project. I presume it was made locally. I have
modelling plaster here in Sweden that really does not
look, feel or behave quite same. This tool is very smooth
with pale off white color and quite hard and durable. It
does not crack or chip as easily as plaster I am used to.
Below are links to pics:

http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_1.jpg
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_2.jpg
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_3.jpg
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_4.jpg


Dominic


From rmay at nethere.com  Wed Apr  1 05:04:23 2009
From: rmay at nethere.com (Bob May)
Date: Tue, 31 Mar 2009 12:04:23 -0800
Subject: [ATM] Help With Spectrophotometer Optics Alignment
References: <000001c9b183$a2d574e0$e8805ea0$@sleeter@roadrunner.com>
Message-ID: <000a01c9b23b$e3e1a400$8f78fea9@amd>

Dave, you know that the thing worked in the past so it isn't that
type of a device.  If the input is a aperture, the lightpath is
different than if it is a slit.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From jkoptic at juno.com  Wed Apr  1 05:17:45 2009
From: jkoptic at juno.com (Jarvis Krumbein)
Date: Tue, 31 Mar 2009 13:17:45 -0700
Subject: [ATM] please ID this tile tool material
Message-ID: <20090331.131745.2500.0.jkoptic@juno.com>

Dominic, the tiles shown in your pictures are ordinary vitreous floor
tiles.  These are readily obtained at most building supply stores here in
the US.  They are also available as square tiles.  The most common size
of either tile is 1" and they come on a backing as sheets 1' X 2'.  These
tiles are hard through their entire thickness unlike the ordinary glazed
tiles and are ideal for tool making.

Jarvis Krumbein

On Tue, 31 Mar 2009 19:52:16 +0200 (MET DST) Dominic-Luc Webb
<dlwebb at canit.se> writes:
> 
> Hoping someone can tell me what this tile tool material is.
> 
> I got it in California, USA years ago (Chabot) together
> with the primary mirror glass I will use for my current
> Mak-Cass project. I presume it was made locally. I have
> modelling plaster here in Sweden that really does not
> look, feel or behave quite same. This tool is very smooth
> with pale off white color and quite hard and durable. It
> does not crack or chip as easily as plaster I am used to.
> Below are links to pics:
> 
>
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar20
09_1.jpg
>
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar20
09_2.jpg
>
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar20
09_3.jpg
>
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar20
09_4.jpg
> 
> 
> Dominic
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 

____________________________________________________________
Click here to choose from a huge selection of shipping supplies!
http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTNawza7Ei6BHzci98uUvKbzKL6hleofnTGJAZKaFP32Ce5wtPNvcU/

From rmay at nethere.com  Wed Apr  1 05:21:48 2009
From: rmay at nethere.com (Bob May)
Date: Tue, 31 Mar 2009 12:21:48 -0800
Subject: [ATM] please ID this tile tool material
References: <Pine.LNX.4.44.0903311941220.12291-100000@uno.canit.se>
Message-ID: <001501c9b23e$526f1d60$8f78fea9@amd>

Dominic, that is probably Hydrocal or Hydrostone.  The tiles are
the porcelin hex tiles used for floors and they come in mats.
The plaster that you've got is probably the typical plaster of
Paris and that needs to be protected from water or it dissolves
into a mush.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From broward32666 at yahoo.com  Wed Apr  1 05:25:23 2009
From: broward32666 at yahoo.com (Charles Broward)
Date: Tue, 31 Mar 2009 13:25:23 -0700 (PDT)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0903311941220.12291-100000@uno.canit.se>
References: <Pine.LNX.4.44.0903311941220.12291-100000@uno.canit.se>
Message-ID: <126937.81044.qm@web110814.mail.gq1.yahoo.com>

Hi,  It looks like it could be Hydrostone.  


Chuck

C.S.Broward
GhastlySky Observatory
Gainesville, Florida


WWW.Floridastars.org
ATM Coord, Alcor




________________________________
From: Dominic-Luc Webb <dlwebb at canit.se>
To: ATM Superheros <atm at atmlist.net>
Sent: Tuesday, March 31, 2009 1:52:16 PM
Subject: [ATM] please ID this tile tool material


Hoping someone can tell me what this tile tool material is.

I got it in California, USA years ago (Chabot) together
with the primary mirror glass I will use for my current
Mak-Cass project. I presume it was made locally. I have
modelling plaster here in Sweden that really does not
look, feel or behave quite same. This tool is very smooth
with pale off white color and quite hard and durable. It
does not crack or chip as easily as plaster I am used to.
Below are links to pics:

http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_1.jpg
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_2.jpg
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_3.jpg
http://www.canit.se/~dlwebb/catadioptric/dlw_12inch_tile_tool_USA_30mar2009_4.jpg


Dominic

_______________________________________________
ATM mailing list http://www.atmlist.net/



      

From hermit at outofoptions.org  Wed Apr  1 05:41:23 2009
From: hermit at outofoptions.org (hermit)
Date: Tue, 31 Mar 2009 16:41:23 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0903311941220.12291-100000@uno.canit.se>
References: <Pine.LNX.4.44.0903311941220.12291-100000@uno.canit.se>
Message-ID: <49D27FF3.5060005@outofoptions.org>

Dominic-Luc Webb wrote:
> Hoping someone can tell me what this tile tool material is.
>
>   

Just check to make sure the base is waterproof.  Doesn't matter after 
that what it is.  I think WillamBell used to sell those kind of tiles.  
The real issue are how hard are they?  I've used some that were way too 
soft.  Soft is good only if you don't want to change ROC much.  If you 
NEED to change ROC,  not good at all.

Ken Lowther

From neil at astronomy.ndo.co.uk  Wed Apr  1 06:35:13 2009
From: neil at astronomy.ndo.co.uk (Neil Booker)
Date: Tue, 31 Mar 2009 22:35:13 +0100
Subject: [ATM] casting Pyrex
References: <20090330.145606.2796.0.hrd9@juno.com>
Message-ID: <01b701c9b248$ead9c6e0$2d7afea9@laura>

Hi Horace and Everyone

Quick question on kilns (I've sent of for "Glass Notes: A Reference Manual
for the Glass Artist. By Henry Halem" that Thomas suggested but hasn't
arrived yet which is why I'm asking here)

Trying to do this cheaply, can I use the elements from old night storage
heaters or are they not up to the sort of temperatures involved in glass
work? Think I can get some cheaply but don't know how long they'll be
available.

Neil


From neil at astronomy.ndo.co.uk  Wed Apr  1 06:35:33 2009
From: neil at astronomy.ndo.co.uk (Neil Booker)
Date: Tue, 31 Mar 2009 22:35:33 +0100
Subject: [ATM] Help With Spectrophotometer Optics Alignment
References: <Pine.LNX.4.44.0903311022050.32082-100000@uno.canit.se>
Message-ID: <01b801c9b248$f041bfc0$2d7afea9@laura>

Hi
----- Original Message ----- 
From: "Dominic-Luc Webb"
To: "ATM Superheros" <atm at atmlist.net>
Sent: Tuesday, March 31, 2009 9:24 AM
Subject: Re: [ATM] Help With Spectrophotometer Optics Alignment


> On Tue, 31 Mar 2009, Dominic-Luc Webb wrote:
> 
> > , so not easy to determine of wavelength is calibrates.
> 
> Yuck, that sentence came out bad! Try:
> 
> ", so no easy way to use glass to calibrate wavelength."

You should see some of the texts I get from my sister :-(

Neil



From richard at foucault.co.uk  Wed Apr  1 07:11:56 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Tue, 31 Mar 2009 23:11:56 +0100
Subject: [ATM] casting Pyrex
In-Reply-To: <01b701c9b248$ead9c6e0$2d7afea9@laura>
References: <20090330.145606.2796.0.hrd9@juno.com>
	<01b701c9b248$ead9c6e0$2d7afea9@laura>
Message-ID: <19067115.20090331231156@foucault.co.uk>

Hello Neil,

Tuesday, March 31, 2009, 10:35:13 PM, you wrote:

> Trying to do this cheaply, can I use the elements from old night storage
> heaters

Definitely not Neil. They are fairly esoteric metal alloys, even Silicon
Carbide for the very high temperature furnaces.

-- 
Best regards,
 Richard in the UK


From thomas at moiler.com  Wed Apr  1 07:17:23 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Wed, 1 Apr 2009 08:17:23 +1000
Subject: [ATM] casting Pyrex
In-Reply-To: <01b701c9b248$ead9c6e0$2d7afea9@laura>
References: <20090330.145606.2796.0.hrd9@juno.com>
	<01b701c9b248$ead9c6e0$2d7afea9@laura>
Message-ID: <010701c9b24e$78e470c0$6aad5240$@com>

Don't skimp on the elements a good set from a reputable maker will save you
$$ in the medium term. I got some new Duralite Nichrome A1 of eBay (I don't
recall the vendor's handle any longer), but a search on kiln elements should
turn up a few possibilities.

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Neil Booker
Sent: Wednesday, 1 April 2009 7:35 AM
To: AMT LIST
Subject: Re: [ATM] casting Pyrex

Hi Horace and Everyone

Quick question on kilns (I've sent of for "Glass Notes: A Reference Manual
for the Glass Artist. By Henry Halem" that Thomas suggested but hasn't
arrived yet which is why I'm asking here)

Trying to do this cheaply, can I use the elements from old night storage
heaters or are they not up to the sort of temperatures involved in glass
work? Think I can get some cheaply but don't know how long they'll be
available.

Neil

_______________________________________________
ATM mailing list http://www.atmlist.net/


From dlwebb at canit.se  Wed Apr  1 16:19:44 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Wed, 1 Apr 2009 09:19:44 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <20090331.131745.2500.0.jkoptic@juno.com>
Message-ID: <Pine.LNX.4.44.0904010911220.2530-100000@uno.canit.se>

On Tue, 31 Mar 2009, Jarvis Krumbein wrote:

> Dominic, the tiles shown in your pictures are ordinary vitreous floor
> tiles.  These are readily obtained at most building supply stores here in
> the US.  They are also available as square tiles.  The most common size
> of either tile is 1" and they come on a backing as sheets 1' X 2'.  These
> tiles are hard through their entire thickness unlike the ordinary glazed
> tiles and are ideal for tool making.
>
> Jarvis Krumbein

On this side note, the black ones are replacements for tiles
that fell out late in grinding. It was not a big deal to
glue the new ones in with urethane glue. The hygrometer
(not calibrated) is there to check humidity. I find the
glue ends up much stronger if I put the tool in the sink
with some water to cover the bottom. Actual humidity was
about RH 90%. Otherwise, indoor RH was below 20%. Next day
I just used a grinding stone to make the new tiles conform
more closely to the ROC of the tool. I will bring this
12" F/5 primary down to about F/3.85 using this repaired
tool.

Dominic


From dlwebb at canit.se  Wed Apr  1 16:26:33 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Wed, 1 Apr 2009 09:26:33 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <49D27FF3.5060005@outofoptions.org>
Message-ID: <Pine.LNX.4.44.0904010920570.2530-100000@uno.canit.se>


On Tue, 31 Mar 2009, hermit wrote:

> Dominic-Luc Webb wrote:
> > Hoping someone can tell me what this tile tool material is.
> >
> >

> Just check to make sure the base is waterproof.  Doesn't matter after
> that what it is.  I think WillamBell used to sell those kind of tiles.
> The real issue are how hard are they?  I've used some that were way too
> soft.  Soft is good only if you don't want to change ROC much.  If you
> NEED to change ROC,  not good at all.
>
> Ken Lowther


Makes sense and not sure what to expect. I am no expert on
relative hardness of different tiles and thought about using
glass instead of those black tiles that are replacements for
the original white ones that broke off. Manually thinning
the black ones on my grinding stone seemed slow, so I
reckoned they were kind of hard. But after I glued the
black ones into the tool, I the experience was very different.
Once the tiles were immobilized and I worked them with the
same grinding stone, like what would be done for bevelling,
I ripped through those tiles real fast. I am already thinking
I really should have stuck with my original place to replace
the lost tiles with glass.

Dominic


From dlwebb at canit.se  Wed Apr  1 16:55:56 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Wed, 1 Apr 2009 09:55:56 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0904010911220.2530-100000@uno.canit.se>
Message-ID: <Pine.LNX.4.44.0904010927310.2530-100000@uno.canit.se>


OK, by most acounts my tool is hydrostone. I know it to
be stabile in water as I have tried leaving it in
water for extended period of time and water did not
change color. No big loss of meterial or tool hardness.
I did not check for swelling. Overall, it seems like
nice material. I wonder if it is one and same as this
Wiki:

http://en.wikipedia.org/wiki/The_Hydrostone

As for dental stone, I once inquired about this, but it
seemed like about the most expensive material one could
use. Here in Sweden I have been using concrete. In some
cases, I have embedded glass into the concrete. With
tool on top, small rocks can fall out, a few hard
enough to scratch. I can seal this obviously. Around
here, one can buy more concrete than can be carried
for about same price as a pizza.

Since I am heading to USA soon, I am thinking to pick up
some of this putative hydrostone, as I do like its
properties, but can't say I feel like this is required
material. Concrete is dirt cheap and goes.

Dominic








From neil at astronomy.ndo.co.uk  Wed Apr  1 18:51:44 2009
From: neil at astronomy.ndo.co.uk (Neil Booker)
Date: Wed, 1 Apr 2009 10:51:44 +0100
Subject: [ATM] casting Pyrex
References: <20090330.145606.2796.0.hrd9@juno.com>
	<01b701c9b248$ead9c6e0$2d7afea9@laura>
	<010701c9b24e$78e470c0$6aad5240$@com>
Message-ID: <006301c9b2b0$4d492fc0$de85fea9@laura>

Hi Thomas & Richard

Thanks. I guess less haste & more speed. I'll wait for the book to arrive
instead of trying to guess what's in it.

Neil


From thomas at moiler.com  Wed Apr  1 21:55:50 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Wed, 1 Apr 2009 22:55:50 +1000
Subject: [ATM] casting Pyrex
In-Reply-To: <006301c9b2b0$4d492fc0$de85fea9@laura>
References: <20090330.145606.2796.0.hrd9@juno.com>	<01b701c9b248$ead9c6e0$2d7afea9@laura>	<010701c9b24e$78e470c0$6aad5240$@com>
	<006301c9b2b0$4d492fc0$de85fea9@laura>
Message-ID: <023601c9b2c9$32a207a0$97e616e0$@com>

Hi Neil,

Probably a good idea that. <grin>

Some rules of thumb to get you started might not be a bad idea at this point
though....

You'll need about 1800W/cubic foot (CF) of kiln volume, if you can get more
than that per CF all the better.
Bank on a minimum of 4" of insulating fire brick (I'd add an inch or two
worth of ceramic fibre blanket to that).
A standard 1/8" wire diameter type K thermocouple will give you very long
service.

I hope the book gets to you soon, sounds like you need the info, I know the
hardest thing for me when I was building my kiln was the waiting, whether it
was for books or for materials/parts....

Oh yeah, here is a glass working yahoo group that you might find interesting
http://groups.yahoo.com/group/glassblowing_topics/ very helpful bunch of
people, and a huge body of knowledge which they share very freely.

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 


-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Neil Booker
Sent: Wednesday, 1 April 2009 7:52 PM
To: 'AMT LIST'
Subject: Re: [ATM] casting Pyrex

Hi Thomas & Richard

Thanks. I guess less haste & more speed. I'll wait for the book to arrive
instead of trying to guess what's in it.

Neil

_______________________________________________
ATM mailing list http://www.atmlist.net/


From dlwebb at canit.se  Thu Apr  2 01:47:19 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Wed, 1 Apr 2009 18:47:19 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0904010920570.2530-100000@uno.canit.se>
Message-ID: <Pine.LNX.4.44.0904011846220.9871-100000@uno.canit.se>


My friend gave a link to pottery place in Richmond, CA that
sells "hydrostone", 50 lbs for 31.90 USD. Sound like right
stuff?

http://claypeople.net/catalog.html

Dominic



From stainless_steel at suddenlink.net  Thu Apr  2 04:17:37 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Wed, 1 Apr 2009 14:17:37 -0500
Subject: [ATM] ATM: Explanation of recent absence-
Message-ID: <4D5886C7BEFD4AD284E969D1367256C1@R101>

Folks:

My landlord has been trouble shooting his one and only working computer with 
components out of mine; it has taken him a week or so to put my video card 
back in my machine. He now has mine back together, and I have enjoyed 
reading latest posts. Turns out my Landlord's high end video card pooped out 
on him. He now has my video card back in my machine, and I am back, as Arnie 
would say in one of his movies.

My landlord is hard on computers. He has five; all five are now deceased. He 
will ultimately kill off this one too.

PS.- The posts have been quite interesting lately; very good reading. Thank 
you all.

DLZ-130
(Davey) 


From rmay at nethere.com  Thu Apr  2 06:37:39 2009
From: rmay at nethere.com (Bob May)
Date: Wed, 1 Apr 2009 13:37:39 -0800
Subject: [ATM] please ID this tile tool material
References: <Pine.LNX.4.44.0904010927310.2530-100000@uno.canit.se>
Message-ID: <001401c9b312$18c4be60$8f78fea9@amd>

I don't know about what is available for plasters there in Sweden
but the stuff you want is the outside statue casting plaster.
That is what Hydrostone is usually used for.  Anybody that is
making outside statues should know what it is.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From colja at internode.on.net  Thu Apr  2 16:05:01 2009
From: colja at internode.on.net (Mike Colja)
Date: Thu, 2 Apr 2009 17:05:01 +1000
Subject: [ATM] please ID this tile tool material
In-Reply-To: <001401c9b312$18c4be60$8f78fea9@amd>
Message-ID: <7o2l9t$a5qgoi@ipmail04.adl2.internode.on.net>

Hydrostone is also used by dentists, and dental supply houses will sell it.
It is very nice to use, can be easily carved, but it does set very fast.
I have used it and had to cast layers to get the right thickness, but this 
Was no problem. I now use concrete (powder) only, no gravel or sand, and it
Has worked very well and is very cheap.

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Bob May
Sent: Thursday, 2 April 2009 7:38 AM
To: atm at atmlist.net
Subject: Re: [ATM] please ID this tile tool material

I don't know about what is available for plasters there in Sweden
but the stuff you want is the outside statue casting plaster.
That is what Hydrostone is usually used for.  Anybody that is
making outside statues should know what it is.
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 b-hamburger at ya.com  Thu Apr  2 17:43:51 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Thu, 2 Apr 2009 10:43:51 +0200
Subject: [ATM] please ID this tile tool material
In-Reply-To: <001401c9b312$18c4be60$8f78fea9@amd>
References: <Pine.LNX.4.44.0904010927310.2530-100000@uno.canit.se>
	<001401c9b312$18c4be60$8f78fea9@amd>
Message-ID: <02ff01c9b36f$26d07ff0$74717fd0$@com>

Hi,

Another remark about dental Stone:
I cannot remember the brand I used to use earlier and found one locally
called GC base stone. However it turns out to be tixotropic (becomes viscous
under pressure), so I did not buy it. A little research showed that quite a
few dental stones show that property, so I guess it would be advisable to
ask before you buy.

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 Bob May
> Sent: mi?rcoles, 01 de abril de 2009 23:38
> To: atm at atmlist.net
> Subject: Re: [ATM] please ID this tile tool material
> 
> I don't know about what is available for plasters there in Sweden
> but the stuff you want is the outside statue casting plaster.
> That is what Hydrostone is usually used for.  Anybody that is
> making outside statues should know what it is.
> 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 neil at astronomy.ndo.co.uk  Thu Apr  2 17:47:58 2009
From: neil at astronomy.ndo.co.uk (Neil Booker)
Date: Thu, 2 Apr 2009 09:47:58 +0100
Subject: [ATM] casting Pyrex
References: <20090330.145606.2796.0.hrd9@juno.com>	<01b701c9b248$ead9c6e0$2d7afea9@laura>	<010701c9b24e$78e470c0$6aad5240$@com>
	<006301c9b2b0$4d492fc0$de85fea9@laura>
	<023601c9b2c9$32a207a0$97e616e0$@com>
Message-ID: <00d001c9b370$40c178a0$ff69fea9@laura>

Hi Thomas

Thanks

Neil



From dlwebb at canit.se  Thu Apr  2 19:02:52 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Thu, 2 Apr 2009 12:02:52 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <02ff01c9b36f$26d07ff0$74717fd0$@com>
Message-ID: <Pine.LNX.4.44.0904021200100.19972-100000@uno.canit.se>

On Thu, 2 Apr 2009, Berthold Hamburger wrote:

> Hi,
>
> Another remark about dental Stone:
> I cannot remember the brand I used to use earlier and found one locally
> called GC base stone. However it turns out to be tixotropic (becomes viscous
> under pressure), so I did not buy it. A little research showed that quite a
> few dental stones show that property, so I guess it would be advisable to
> ask before you buy.
>
> Berthold

I thought this was common property. Are you saying this is
unique or more pronounced in dental stone? I wonder if
the unique manufacturing process using pressure to make
dental stone gypsum is related?

Dominic


From b-hamburger at ya.com  Thu Apr  2 19:35:36 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Thu, 2 Apr 2009 12:35:36 +0200
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0904021200100.19972-100000@uno.canit.se>
References: <02ff01c9b36f$26d07ff0$74717fd0$@com>
	<Pine.LNX.4.44.0904021200100.19972-100000@uno.canit.se>
Message-ID: <030a01c9b37e$d822f2b0$8868d810$@com>

Hi Dominic,

Apparently some dental stones advertise the tixotropic property and others don't. Since for dentistry tixotropic properties are a feature (to my understanding) and not a bug, I would imagine that those that don't mention it don't posses this property. In GC base stone you control viscosity by mixing with different quantities of water.

Anyway, I am in touch with 2 manufacturers whom I will ask about the technical properties of their product. One is Heraeus Kulzer and the other is Kerr. The first one is substantially cheaper and sells 25kg for aprox. 50? while the other costs around 90? for that quantity.

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 Dominic-Luc Webb
> Sent: jueves, 02 de abril de 2009 12:03
> To: ATM Superheros
> Subject: Re: [ATM] please ID this tile tool material
> 
> On Thu, 2 Apr 2009, Berthold Hamburger wrote:
> 
> > Hi,
> >
> > Another remark about dental Stone:
> > I cannot remember the brand I used to use earlier and found one locally
> > called GC base stone. However it turns out to be tixotropic (becomes
> viscous
> > under pressure), so I did not buy it. A little research showed that
> quite a
> > few dental stones show that property, so I guess it would be advisable
> to
> > ask before you buy.
> >
> > Berthold
> 
> I thought this was common property. Are you saying this is
> unique or more pronounced in dental stone? I wonder if
> the unique manufacturing process using pressure to make
> dental stone gypsum is related?
> 
> Dominic
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From rmay at nethere.com  Fri Apr  3 04:43:45 2009
From: rmay at nethere.com (Bob May)
Date: Thu, 2 Apr 2009 11:43:45 -0800
Subject: [ATM] please ID this tile tool material
References: <02ff01c9b36f$26d07ff0$74717fd0$@com><Pine.LNX.4.44.0904021200100.19972-100000@uno.canit.se>
	<030a01c9b37e$d822f2b0$8868d810$@com>
Message-ID: <000f01c9b3cb$56659280$8f78fea9@amd>

Didn't realize that plasters have that property!  Everything that
I've seen has always made up a nicce hard stone.  I even recently
cut a support for a mirror on my table saw to cut down on its
thickness for a box to hold the mirror.  Cut real nicely and just
like a soft stone of fair brittleness.  The piece cut off even
rang nicely like a bell when struck!
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From stainless_steel at suddenlink.net  Fri Apr  3 07:08:08 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Thu, 2 Apr 2009 17:08:08 -0500
Subject: [ATM] ATM: Re: Please ID this tile tool material-
Message-ID: <5A6860DBA6514E139059DDFB21534D88@R101>


As I mentioned in this august forum ages ago, I once read where an 
accomplisheed ATM said, in print in a regular publication: "Dental Stone is 
not dimensionally stable." Hence, my mostly silica based base for the hex 
tiles in this article:

http://www.atmsite.org/contrib/Harbour/Tool.html

DLZ-130


>Hi,

>Another remark about dental Stone:
>I cannot remember the brand I used to use earlier and found one locally
>called GC base stone. However it turns out to be tixotropic (becomes 
>viscous
>under pressure), so I did not buy it. A little research showed that quite a
>few dental stones show that property, so I guess it would be advisable to
>ask before you buy.

>Berthold

-- 
Berthold Hamburger - Cellist/Spain
Email: behambu at artinso.com
http://www.artinso.com
http://www.astro.artinso.com



From Mitch_Bisnauth at Cknainc.com  Fri Apr  3 22:36:50 2009
From: Mitch_Bisnauth at Cknainc.com (Mitch_Bisnauth at Cknainc.com)
Date: Fri, 3 Apr 2009 08:36:50 -0500
Subject: [ATM] Thixotropic Dental Stone
In-Reply-To: <5A6860DBA6514E139059DDFB21534D88@R101>
Message-ID: <OFF18EF434.14AECEF0-ON8625758D.004A49BF-8625758D.004AD9AC@Cknainc.com>

Is this thixothropia in its solid/cured state?

MitchB

From b-hamburger at ya.com  Fri Apr  3 23:14:57 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Fri, 3 Apr 2009 16:14:57 +0200
Subject: [ATM] Thixotropic Dental Stone
In-Reply-To: <OFF18EF434.14AECEF0-ON8625758D.004A49BF-8625758D.004AD9AC@Cknainc.com>
References: <5A6860DBA6514E139059DDFB21534D88@R101>
	<OFF18EF434.14AECEF0-ON8625758D.004A49BF-8625758D.004AD9AC@Cknainc.com>
Message-ID: <038b01c9b466$92388010$b6a98030$@com>

According to the manufacturer you decide upon the grade of thixothropia
during mixing, so I guess it refers to its solid state.

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 Mitch_Bisnauth at Cknainc.com
> Sent: viernes, 03 de abril de 2009 15:37
> To: ATM list; atm-bounces at atmlist.net
> Subject: [ATM] Thixotropic Dental Stone
> 
> Is this thixothropia in its solid/cured state?
> 
> MitchB
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From vladimir.galogaza1 at zg.t-com.hr  Sat Apr  4 04:03:40 2009
From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza)
Date: Fri, 3 Apr 2009 21:03:40 +0200
Subject: [ATM] Thixotropic Dental Stone
References: <OFF18EF434.14AECEF0-ON8625758D.004A49BF-8625758D.004AD9AC@Cknainc.com>
Message-ID: <A5D586EBBBC449E8A01DE821FD45EF62@piv555a133b59e>

Mitch,

>Is this thixothropia in its solid/cured state?

"Thyxotropic: Having the property of certain resins and paints that prevents 
them from running off vertical surfaces"

In case of substance like  plasters it is important that they can be applied
on vertical surfaces without running off quickly before they solidify.

Generally thyxotropic means that substance at rest behaves like solid, 
while
if agitated behaves like liquid. In case of plaster you can apply it like 
gel or viscous
liquid while after application and before cured,  it will stay on the 
surface until cured.
When cured it is not more thyxotropic but solid, like dental stone.
Saying that solid material is thyxotropic would be contradiction in meaning.

Substances are advertised as being thyxotropic when it is important for 
handling
during application, even if they never solidify and it is even not supposed 
that they do.

Regards
Vladimir.




From rmay at nethere.com  Sat Apr  4 05:14:28 2009
From: rmay at nethere.com (Bob May)
Date: Fri, 3 Apr 2009 12:14:28 -0800
Subject: [ATM] Thixotropic Dental Stone
References: <OFF18EF434.14AECEF0-ON8625758D.004A49BF-8625758D.004AD9AC@Cknainc.com>
	<A5D586EBBBC449E8A01DE821FD45EF62@piv555a133b59e>
Message-ID: <000c01c9b498$cb9a8560$8f78fea9@amd>

I guess that means that when I mix it thick and it stays in a
nice pile then it is and when I mix it like a soup, it isn't.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From holmmarkd at gmail.com  Sat Apr  4 07:35:15 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Fri, 03 Apr 2009 18:35:15 -0400
Subject: [ATM] Thixotropic Dental Stone
In-Reply-To: <000c01c9b498$cb9a8560$8f78fea9@amd>
References: <OFF18EF434.14AECEF0-ON8625758D.004A49BF-8625758D.004AD9AC@Cknainc.com>	<A5D586EBBBC449E8A01DE821FD45EF62@piv555a133b59e>
	<000c01c9b498$cb9a8560$8f78fea9@amd>
Message-ID: <49D68F23.6020901@gmail.com>

Honestly, guys, I don't think thixotropy is a property to worry about in 
tool materials.  If a material is thixotropic, you will have to push it 
a bit harder to get it into shape, and it will tend to hold that shape 
after you push it.  Since we are talking about making grinding tools, we 
are only trying to get a short cylinder with some embedded tiles, not a 
complex part with long runs.  If the plaster will run enough to go 
between the tiles and let us flatten off the back side reasonably, we 
are golden.  A whole lot of us have made perfectly good tools with 
dental stone of various grades and manufacturers, and with Hydrostone 
and Hydrocal.  The stuff works. Just get some and go.  If you have 
problems, then come back here and bitch at us.  Worry less, make more tools!

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From mokiman_210 at yahoo.com  Sat Apr  4 09:45:33 2009
From: mokiman_210 at yahoo.com (Curt Diggs)
Date: Fri, 3 Apr 2009 17:45:33 -0700 (PDT)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <mailman.1494.1238785073.6544.atm@atmlist.net>
References: <mailman.1494.1238785073.6544.atm@atmlist.net>
Message-ID: <887705.42783.qm@web50403.mail.re2.yahoo.com>

Hi, Dominic,

Here's?a link to the manufacturer's website (US Gypsum) that has all the properties of Hydro-Stone. It's all I use for tools. 

http://gypsumsolutions.com/application.asp?prod=20&app=Art+and+Statuary

As Bob said, its main use is exterior statuary so it's completely?waterproof (as far as I can tell). It need no sealing and holds small ceramic tiles very well.

Curt Diggs

------------------------------

Message: 13
Date: Wed, 1 Apr 2009 18:47:19 +0200 (MET DST)
From: Dominic-Luc Webb <dlwebb at canit.se>
Subject: Re: [ATM] please ID this tile tool material
To: ATM Superheros <atm at atmlist.net>
Message-ID: <Pine.LNX.4.44.0904011846220.9871-100000 at uno.canit.se>
Content-Type: TEXT/PLAIN; charset=US-ASCII


My friend gave a link to pottery place in Richmond, CA that
sells "hydrostone", 50 lbs for 31.90 USD. Sound like right
stuff?

http://claypeople.net/catalog.html

Dominic


      

From holmmarkd at gmail.com  Sat Apr  4 10:38:55 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Fri, 03 Apr 2009 21:38:55 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <887705.42783.qm@web50403.mail.re2.yahoo.com>
References: <mailman.1494.1238785073.6544.atm@atmlist.net>
	<887705.42783.qm@web50403.mail.re2.yahoo.com>
Message-ID: <49D6BA2F.6000707@gmail.com>

A point about plaster.  It applies even more to portland cement products 
such as "cement" and "concrete".  These things slowly absorb water 
and/or carbon dioxide from the air.  They will, in time, become 
useless.  So, for storage, bundle them inside good polyethylene bags, 
such as heavy duty trash bags and seal as best as you can.  Will get 
better shelf life that way.

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From shane at ct-astronomer.com  Sun Apr  5 12:57:42 2009
From: shane at ct-astronomer.com (Shane LaPierre)
Date: Sat, 4 Apr 2009 23:57:42 -0400
Subject: [ATM] Can anybody test an 8" flat I have?
Message-ID: <88E82EAB-91B8-4798-97E5-9B847A540899@ct-astronomer.com>

I have an 8" flat that I would like to test to see if it is flat  
enough to use... but I don't have another suitable flat to test  
against.  Just hoping somebody can do an interference test, and  
quantify the overall results.  I have good reason to believe it's a  
suitable flat for making a paraboloid, but I'm not building a rig  
around it until I know for sure.

Just let me know, and hopefully we can work out a suitable arrangement.

Thanks,
Shane LaPierre

From donald_clement at yahoo.com  Mon Apr  6 03:15:45 2009
From: donald_clement at yahoo.com (don clement)
Date: Sun, 5 Apr 2009 11:15:45 -0700 (PDT)
Subject: [ATM] sine generator (an IT perspective)
Message-ID: <840081.55836.qm@web34207.mail.mud.yahoo.com>


Yeah Vista works alright. I just a purchased a computational intensive program to run non-linear FEA analysis on a PC for optimizing my focuser design. Although the software is made to run with Vista as the OS, Solidworks advised me to run 64 bit XP instead. Also when looking for a PC with enough RAM and speed to run this software it is interesting that that Dell offers a PC with Vista OS but with a ?downgrade? to XP. XP is not only still supported and available but is actually recommended by a major software provider for use in place of Vista bloatware.

Don Clement
Running Springs, California 



--- On Wed, 12/10/08, stainless_steel at suddenlink.net <stainless_steel at suddenlink.net> wrote:

> From: stainless_steel at suddenlink.net <stainless_steel at suddenlink.net>
> Subject: Re: [ATM] sine generator (an IT perspective)
> To: donald_clement at yahoo.com, "ATM list" <atm at atmlist.net>
> Date: Wednesday, December 10, 2008, 6:42 AM

> Wait until the PC industry burns that
> bridge behind you. Then you will have to see how well or not
> so well, Vista works.
> 
> 
> ----- Original Message ----- From: "don clement" <donald_clement at yahoo.com>
> To: "ATM list" <atm at atmlist.net>
> Sent: Tuesday, December 09, 2008 4:44 PM
> Subject: Re: [ATM] sine generator (an IT perspective)
> 
> 
> > You forgot those that just don't want to put out the
> $$ needed to upgrade older application software that won't
> run on Vista. For me XP works just fine and isn't the
> hardware hog that Vista is. Also remember Fourier and
> transient waveforms are composed of a series of sinewaves.
> The real world isn't all periodic and regular...unless
> viewed as an infinte series of periodic sinewaves.
> > 
> > 
> > --- On Tue, 12/9/08, Scope Builder <scopebuilder at gmail.com>
> wrote:
> > 
> >> From: Scope Builder <scopebuilder at gmail.com>
> >> Subject: Re: [ATM] sine generator (an IT
> perspective)
> >> To: "ATM list" <atm at atmlist.net>
> >> Date: Tuesday, December 9, 2008, 6:43 AM
> >> Has anyone else ever noticed that it's primarily
> the
> >> same small group of
> >> people complaining about their software over and
> over?
> >> What's really going
> >> on?
> >> 
> >> I've got literally dozens of common ATM and
> astronomy
> >> software packages,
> >> from Figure XP to Stellarium and beyond, on my
> Windows
> >> Vista machine, and
> >> they run great.? AND I have Vista's Automatic
> Updates
> >> running every day,
> >> too.
> >> 
> >> Guess what???? They ran fine when I had
> Windows XP, too!
> >> 
> >> I'm also an IT director overseeing literally
> dozens and
> >> dozens of Windows
> >> Vista PC's that run flawlessly every day.?
> How is that
> >> we can get our
> >> machines to run fine, but the complainers can't?
> >> 
> >> I've found several things over the years that can
> hurt
> >> an operating system
> >> (even Windows Vista):
> >>? ???- Viruses, Trojans, Worms,
> Spyware, etc., etc., etc.
> >> (Mostly from
> >> non-use of anti-virus or other prevention
> software.)
> >>? ???- Installing freeware and
> other software of
> >> questionable design.
> >>? ???- Hardware levels below
> software requirements
> >>? ???- Unwillingness to install
> an adequate amount of memory
> >> in the PC.
> >>? ???- Unwillingness to keep an
> adequate amount of
> >> hard-drive space free.
> >>? ???- Wrong hardware drivers
> for pc hardware (or wrong
> >> version)
> >>? ???- Inadequately trained
> operators
> >> 
> >> Notice anything with this list?? The
> operating system
> >> itself isn't on it!!!
> >> 
> >> In the few Vista issues we've actually had, I've
> >> found errors that appeared
> >> to be operating system have resolved by fixing
> problems not
> >> associated with
> >> the operating system itself, mostly due to memory
> or virus
> >> type info.
> >> 
> >> This sounds more like they have inadequate memory
> >> installed, saturated
> >> hard-drive, poorly written code, or some incorrect
> driver
> >> version is
> >> installed in their machines, rather than it being
> a true
> >> Vista issue.
> >> 
> >> Think cars.? If you drop a brand-new high
> performance
> >> engine in a vehicle,
> >> then clog the fuel tank and take the air out of
> the tires,
> >> you're going to
> >> be in the repair shop all the time.? Just
> don't whine
> >> about the engine like
> >> an old welfare grandmother when it happens.
> >> 
> >> My 2 cents.
> >> 
> >> 
> >> ----- Original Message ----- >> Is it any
> wonder that I'm running Windoz 98SE?
> >>? It has proven to
> >> >> be a fair it more reliable than almost
> anything
> >> laeer.
> >> >> I'd suggest that anytime that you find a
> >> problem iwth Vista is to
> >> >> clean off the disk and reload Vista.
> >> >
> >> > There is some wisdom in that suggestion
> <name
> >> removed>! I have one
> >> > computer
> >> > running Vista at home, and every time it does
> another
> >> update, another
> >> > piece of software quits working. My favorite
> radio
> >> control software
> >> > was nuked by my latest update, so I think
> I'm
> >> going to have to go back
> >> > and reinstall the OS, then update to just
> before this
> >> point. Sheesh.
> >> 



      

From rmay at nethere.com  Mon Apr  6 07:59:18 2009
From: rmay at nethere.com (Bob May)
Date: Sun, 5 Apr 2009 15:59:18 -0700
Subject: [ATM] Can anybody test an 8" flat I have?
References: <88E82EAB-91B8-4798-97E5-9B847A540899@ct-astronomer.com>
Message-ID: <000201c9b642$6677e500$8f78fea9@amd>

I've got two 12" flats but, unfortunately, they are coated and
have 2" holes in the middle which makes for weak fringes.  I'm in
the San Diego area.
Another way to test is to grab a bigger sphere (a mirror that you
haven't parabolized yet) and get it to a good sphere.  Reflect
the light from the tester at a 45 degree angle through the flat
and see what the difference is.  Not much of a change from a
standard Foucault test but it works and works well.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Mon Apr  6 08:03:22 2009
From: rmay at nethere.com (Bob May)
Date: Sun, 5 Apr 2009 16:03:22 -0700
Subject: [ATM] sine generator (an IT perspective)
References: <840081.55836.qm@web34207.mail.mud.yahoo.com>
Message-ID: <000501c9b642$bd6b6a80$8f78fea9@amd>

The next version of windoz is available from the microcrud
website but it is 2.2GB of download!  It is supposed to be much
better than the blocked view.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From alaskawolfjoe at hotmail.com  Mon Apr  6 12:21:16 2009
From: alaskawolfjoe at hotmail.com (lance clarke)
Date: Sun, 5 Apr 2009 23:21:16 -0400
Subject: [ATM] mirror coaters in Canada
Message-ID: <COL113-W217416596F7D23E420437FA8840@phx.gbl>


A few weeks ago, there was a discussion of mirror coaters in Canada, and I listed AJ's, Moonward, and Francois St. Martin.  It has since come to my attention that Francois has changed his email from what I listed.

He now can be contacted at francoisstmartin at cooptel.qc.ca .  Apparently he is also soon going to be able to aluminize mirrors up to 24 inches. (Good news, as I'm working on an 18"!).

 

While I'm on the subject, I just saw that Stellafane just received a donation of a vacuum coater.  Anyone know what size it will accomodate?

 

Lance

_________________________________________________________________
Experience all of the new features, and Reconnect with your life.
http://go.microsoft.com/?linkid=9650730

From dlwebb at canit.se  Mon Apr  6 17:41:02 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Mon, 6 Apr 2009 10:41:02 +0200 (MET DST)
Subject: [ATM] sine generator (an IT perspective)
In-Reply-To: <840081.55836.qm@web34207.mail.mud.yahoo.com>
Message-ID: <Pine.LNX.4.44.0904061033480.1600-100000@uno.canit.se>

On Sun, 5 Apr 2009, don clement wrote:

>
> I just a purchased a computational intensive program to
> run non-linear FEA analysis on a PC for optimizing my
> focuser design.
>
> Don Clement
> Running Springs, California


Hi Don,

Side-tracking here, does this mean you are going to improve
on your famous Clement focuser? I wonder what is the next
generation?

Dominic


From truckeratm at sbcglobal.net  Mon Apr  6 20:44:59 2009
From: truckeratm at sbcglobal.net (Jerry Hillman)
Date: Mon, 6 Apr 2009 04:44:59 -0700 (PDT)
Subject: [ATM] Woodworking help needed
Message-ID: <545698.71564.qm@web180101.mail.gq1.yahoo.com>


To all the Master Woodworkers on the list,
I have seen some of the absolutely beautiful work some of you have done. I need a little help.
I just acquired a 6" planer/jointer from my step-dad. Amoung other things I want to use this to build a nice telescope mount for my 10" and my 15". I have gradually been getting the tools together to start a woodworking business since I can no longer drive a truck, or drive at all.
I have cleaned this tool, removed all the rust from the table and fence, removed, cleaned, and sharpened the blades and put it all back together according to the owners manual instructions. It is made by Craftsman so that tells something else about it. It creates wedges when I run boards through it. What is wrong?
Jerry B

From thomas at moiler.com  Mon Apr  6 20:51:58 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Mon, 6 Apr 2009 21:51:58 +1000
Subject: [ATM] Woodworking help needed
In-Reply-To: <545698.71564.qm@web180101.mail.gq1.yahoo.com>
References: <545698.71564.qm@web180101.mail.gq1.yahoo.com>
Message-ID: <021301c9b6ae$18d46ff0$4a7d4fd0$@com>

Two possible faults, one the blades are not aligned properly (and there may
be a way to do this without removing them) on the drum, the other is the
table maybe out of wack to the blade drum axis.

There are probably more possible things to look for, but I can't of any of
the top of my head right now.

When you mounted the blades were there some bolts that "didn't" seem to
actually hold the blades in place but were right close to the blades? If so
these are the ones to look at first.

Good luck with the new venture!

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Jerry Hillman
Sent: Monday, 6 April 2009 9:45 PM
To: atm at atmlist.net
Subject: [ATM] Woodworking help needed


To all the Master Woodworkers on the list,
I have seen some of the absolutely beautiful work some of you have done. I
need a little help.
I just acquired a 6" planer/jointer from my step-dad. Amoung other things I
want to use this to build a nice telescope mount for my 10" and my 15". I
have gradually been getting the tools together to start a woodworking
business since I can no longer drive a truck, or drive at all.
I have cleaned this tool, removed all the rust from the table and fence,
removed, cleaned, and sharpened the blades and put it all back together
according to the owners manual instructions. It is made by Craftsman so that
tells something else about it. It creates wedges when I run boards through
it. What is wrong?
Jerry B
_______________________________________________
ATM mailing list http://www.atmlist.net/


From richard at foucault.co.uk  Mon Apr  6 21:49:59 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Mon, 6 Apr 2009 13:49:59 +0100
Subject: [ATM] Woodworking help needed
In-Reply-To: <545698.71564.qm@web180101.mail.gq1.yahoo.com>
References: <545698.71564.qm@web180101.mail.gq1.yahoo.com>
Message-ID: <767237519.20090406134959@foucault.co.uk>

Hello Jerry,

Monday, April 6, 2009, 12:44:59 PM, you wrote:

> I just acquired a 6" planer/jointer from my step-dad.
> ...
> It creates wedges when I run boards through it. What is wrong?

I agree with Thomas, it does sound like blade alignment.

Do you have a good straight edge or can you borrow one?. A good 3 ft
straight edge is essential to setting up a jointer. Isolate the power.
Wind the table up so that input and output tables are level then lay
the straight edge along the table each side of the blade. Test across
the full width that the input and output tables are completely
parallel. Now rotate the blade holder by hand until a blade is at the
peak of its cutting height. Set one end the blade so it just touches
the straight edge, then do the same at the other end of the blade.
Check that the blade can just touch the straight edge across the full
width of the table. Rotating the blade holder slightly can help with
this, but try to do it in reverse direction to avoid damaging the
straight edge. Repeat this for the other blade(s). If the thickness
scale can be adjusted, now is a good time to set it to zero. Last job
is to set the fence square to the table, checking for square along its
length. Make absolutely certain that the blades are tight before
putting it back into use.

Just to be sure we are talking about the same thing, to me a jointer
is open and you manually push the wood onto the table and over the top
of the blades to flatten one face of the wood. A planer-thicknesser is
closed and you push the wood over an adjustable table and *under* the
blades to plane the good to a given thickness. I am assuming you mean
the jointer.

-- 
Best regards,
 Richard in the UK


From rsackett00 at yahoo.com  Mon Apr  6 21:55:27 2009
From: rsackett00 at yahoo.com (Ross Sackett)
Date: Mon, 6 Apr 2009 05:55:27 -0700 (PDT)
Subject: [ATM] Woodworking help needed
Message-ID: <393445.84488.qm@web59206.mail.re1.yahoo.com>


Jerry,

Which way are the boards wedged?  If there is a change in thickness along the length of the board, it is probably snipe and you need to adjust the level of your infeed and outfeed tables.  If the variation is side to side across the width then you need to make sure the blades are parallel to each other and to the tables--you might need to adjust the blades or just adjust/shim the tables.  There are descriptions of these processes online.

Ross

--- On Mon, 4/6/09, Jerry Hillman <truckeratm at sbcglobal.net> wrote:

> From: Jerry Hillman <truckeratm at sbcglobal.net>
> Subject: [ATM] Woodworking help needed
> To: atm at atmlist.net
> Date: Monday, April 6, 2009, 6:44 AM
> 
> To all the Master Woodworkers on the list,
> I have seen some of the absolutely beautiful work some of
> you have done. I need a little help.
> I just acquired a 6" planer/jointer from my step-dad.
> Amoung other things I want to use this to build a nice
> telescope mount for my 10" and my 15". I have gradually been
> getting the tools together to start a woodworking business
> since I can no longer drive a truck, or drive at all.
> I have cleaned this tool, removed all the rust from the
> table and fence, removed, cleaned, and sharpened the blades
> and put it all back together according to the owners manual
> instructions. It is made by Craftsman so that tells
> something else about it. It creates wedges when I run boards
> through it. What is wrong?
> Jerry B
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 

From dlwebb at canit.se  Mon Apr  6 22:08:30 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Mon, 6 Apr 2009 15:08:30 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <7o2l9t$a5qgoi@ipmail04.adl2.internode.on.net>
Message-ID: <Pine.LNX.4.44.0904061505001.21387-100000@uno.canit.se>


On Thu, 2 Apr 2009, Mike Colja wrote:

> Was no problem. I now use concrete (powder) only, no gravel or sand, and it
> Has worked very well and is very cheap.

Hmmm... concrete without gravel or sand. Is this not refered to
as "cement"? Does this harden OK on its own without sand? Do
you use additives, like water-proofing, binding agents, etc?


Dominic


From richard at foucault.co.uk  Tue Apr  7 00:24:15 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Mon, 6 Apr 2009 16:24:15 +0100
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0904061505001.21387-100000@uno.canit.se>
References: <7o2l9t$a5qgoi@ipmail04.adl2.internode.on.net>
	<Pine.LNX.4.44.0904061505001.21387-100000@uno.canit.se>
Message-ID: <1403544071.20090406162415@foucault.co.uk>

Hello Dominic-Luc,

Monday, April 6, 2009, 2:08:30 PM, you wrote:

> Hmmm... concrete without gravel or sand. Is this not refered to
> as "cement"? Does this harden OK on its own without sand? Do
> you use additives, like water-proofing, binding agents, etc?

Concrete = portland cement + water + sand + aggregate
Cement = portland cement + water + sand
Grout = portland cement + water

Portland cement will harden even in the bag due to humidity. It should
always be used fresh, preferably still warm from the mill :)

-- 
Best regards,
 Richard in the UK


From dlwebb at canit.se  Tue Apr  7 01:28:09 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Mon, 6 Apr 2009 18:28:09 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <1403544071.20090406162415@foucault.co.uk>
Message-ID: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>


On Mon, 6 Apr 2009, Richard in the UK wrote:

> Concrete = portland cement + water + sand + aggregate
> Cement = portland cement + water + sand
> Grout = portland cement + water
>
> Portland cement will harden even in the bag due to humidity. It should
> always be used fresh, preferably still warm from the mill :)
>
> --
> Best regards,
>  Richard in the UK

Could you be mixing (pardon the pun) cement and grout?
>From Wikipedia:

"Grout is generally composed of a mixture of water, cement,
sand and sometimes fine gravel (if it is being used to fill
the cores of cement blocks)."

Portland cement is the most common cement, which I take to mean
there are others.

I have seen sand refered to as fine aggregate and gravel as
aggregate (I presume crushed granite or some such).

Dominic


From richard at foucault.co.uk  Tue Apr  7 01:46:13 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Mon, 6 Apr 2009 17:46:13 +0100
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
References: <1403544071.20090406162415@foucault.co.uk>
	<Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
Message-ID: <1184829206.20090406174613@foucault.co.uk>

Hello Dominic-Luc,

Monday, April 6, 2009, 5:28:09 PM, you wrote:

> Could you be mixing (pardon the pun) cement and grout?
>>From Wikipedia:

No, I never heard of sand in grout. Cement sand and water is cement,
period. "Just because it is on Wikipedia doesn't mean it's right"

-- 
Best regards,
 Richard in the UK


From mjc5 at psu.edu  Tue Apr  7 02:08:27 2009
From: mjc5 at psu.edu (Michael Coslo)
Date: Mon, 06 Apr 2009 13:08:27 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <1184829206.20090406174613@foucault.co.uk>
References: <1403544071.20090406162415@foucault.co.uk>
	<Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<1184829206.20090406174613@foucault.co.uk>
Message-ID: <D9CED295-8316-4929-ACC9-2F50E99F4324@psu.edu>


On Apr 6, 2009, at 12:46 PM, Richard in the UK wrote:

> Hello Dominic-Luc,
>
> Monday, April 6, 2009, 5:28:09 PM, you wrote:
>
>> Could you be mixing (pardon the pun) cement and grout?
>>> From Wikipedia:
>
> No, I never heard of sand in grout. Cement sand and water is cement,
> period. "Just because it is on Wikipedia doesn't mean it's right"


My wife works in the flooring industry, and according to her, grout is  
grout. If there is sand in it, it is called (ohh I feel like I'm  
making a dumb joke here) Sanded grout.



-73 de Mike N3LI -



From TPolk at decatur-al.gov  Tue Apr  7 02:44:51 2009
From: TPolk at decatur-al.gov (Polk, Tom)
Date: Mon, 6 Apr 2009 12:44:51 -0500
Subject: [ATM] please ID this tile tool material
In-Reply-To: <1184829206.20090406174613@foucault.co.uk>
References: <1403544071.20090406162415@foucault.co.uk><Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<1184829206.20090406174613@foucault.co.uk>
Message-ID: <398213C674F7554AB0F55401DF29FBD101F8BAA2@ziggy.decatur-al.net>

Hello,

Cement sand and water = mortar
At least in my part of the world.

Cement is the bonding agent for concrete, grout, mortar.

See "Design and Control of Concrete Mixtures" pub. Portland Cement
Assoc., or just go to Wikipedia for basic information. 

For tool use (our use), just remember to use (at least) 33% cement for
usable strength. Use masonry or "sharps" sand instead of "play-box"
sand.

I may be straying off topic, sorry. 


Tom Polk

*SNIP*

No, I never heard of sand in grout. >>This will depend on the
application. I see it in anchor bolt grout.<<
Cement sand and water is cement, period. >>Look at your sentence. Cement
is an ingredient in a variety mixes.<<
"Just because it is on Wikipedia doesn't mean it's right" >>Do you have
on a flameproof suit?<<



From rmay at nethere.com  Tue Apr  7 05:05:14 2009
From: rmay at nethere.com (Bob May)
Date: Mon, 6 Apr 2009 13:05:14 -0700
Subject: [ATM] Woodworking help needed
References: <545698.71564.qm@web180101.mail.gq1.yahoo.com>
Message-ID: <001601c9b6f3$00ee5fa0$8f78fea9@amd>

The first suspect is that the blades aren't in correctly.  There
is a little magnetic tool that will assist in putting the blades
in right.
Second is that the is a tilt in the two tables.
Third, there is a tilt in the fence (end cuts not being square).
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Tue Apr  7 05:11:12 2009
From: rmay at nethere.com (Bob May)
Date: Mon, 6 Apr 2009 13:11:12 -0700
Subject: [ATM] please ID this tile tool material
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
Message-ID: <002501c9b6f3$d5ca8fa0$8f78fea9@amd>

We're running into regional phraseology here.  Some call it
cement, others call it sand and cement (or something else like
that) and so forth.
What you want if you're going to use cement is the stuff with no
sand in it, just the stuff that does the chemical reaction to
make stone.
I've used some of the stuff but don't really like it as it seems
to be a bit soft and flaky.  The mix with the sand in it
definitely does not work!  The sand comes off and you'd have to
use some of Richard's Secret Sauce to seal it to keep the sand
from falling off and I'd not use it for grinding for that reason.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From TPolk at decatur-al.gov  Tue Apr  7 05:33:30 2009
From: TPolk at decatur-al.gov (Polk, Tom)
Date: Mon, 6 Apr 2009 15:33:30 -0500
Subject: [ATM] please ID this tile tool material
In-Reply-To: <002501c9b6f3$d5ca8fa0$8f78fea9@amd>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
Message-ID: <398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>

I agree, trade names are regional.

Without something to bind with, 100% cement is no good. One part cement,
two parts sharp sand mixed as lean as possible with water (but a
cohesive mixture). Allow to hydrate (keep moist) about 28 days for good
compressive strength. Oven dry it ~150-175F. Epoxy seal it. Epoxy the
tiles. A cheap tool is born.

There are many suitable materials to make a tile tool with. Recently I
used a 6" tool to hog and fine grind an 8" f/6 to f/4.0. The 6" tool was
a 0.375" thick piece of A36 steel and the tiles were held with pitch.
The pitch was very hard and poured thin (~1/16"). Placed in cool water.
The channels were not fully cut to the steel. It took about ~45 minutes
to have a tile tool up and running on the Mirror-Matic.

Tom Polk

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf
Of Bob May
Sent: Monday, April 06, 2009 3:11 PM
To: atm at atmlist.net
Subject: Re: [ATM] please ID this tile tool material

We're running into regional phraseology here.  Some call it
cement, others call it sand and cement (or something else like
that) and so forth.
What you want if you're going to use cement is the stuff with no
sand in it, just the stuff that does the chemical reaction to
make stone.
I've used some of the stuff but don't really like it as it seems
to be a bit soft and flaky.  The mix with the sand in it
definitely does not work!  The sand comes off and you'd have to
use some of Richard's Secret Sauce to seal it to keep the sand
from falling off and I'd not use it for grinding for that reason.
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 kmreid1 at shaw.ca  Tue Apr  7 06:08:50 2009
From: kmreid1 at shaw.ca (KR)
Date: Mon, 6 Apr 2009 14:08:50 -0700
Subject: [ATM] please ID this tile tool material
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
Message-ID: <C3A557D10668466C9131416571597961@Holly>


----- Original Message ----- 
From: "Polk, Tom" <TPolk at decatur-al.gov>
To: <atm at atmlist.net>
Sent: Monday, April 06, 2009 1:33 PM
Subject: Re: [ATM] please ID this tile tool material


>I agree, trade names are regional.
Portland cement with minimal water (no addatives) ; good for 18 months 
before developing cracks. Some suggest fiberglass filler for longer life. 
Keep it wet for a few days.
KR 


From truckeratm at sbcglobal.net  Tue Apr  7 06:48:02 2009
From: truckeratm at sbcglobal.net (Jerry Hillman)
Date: Mon, 6 Apr 2009 14:48:02 -0700 (PDT)
Subject: [ATM]  Planer/jointer working
Message-ID: <398005.82814.qm@web180110.mail.gq1.yahoo.com>


Hi Guys,
Thanks for your input.  It took all day, but the jointer will now do what it it supposed to do.  I did not get the blades set correctly the first time, but they were only off less than the thickness of a sheet of paper.  I reset them. They are not off now.
The bigger problem was debris buildup on the underneath side of the infeed table. Until I get my workshop built this fall I am working at a disadvantage. I don't have good lighting in my current shop. This will be corrected but I had to crawl under the jointer with a shop light to level it. That is when I found such stuff as mud dobber (black wasp) nests and a lot of old sawdust and sap built up in the mechanisms.
I removed the infeed table, cleaned it and reinstalled it.  It has been a challenge due to the design but I got it perfectly level. Okay, within .001" or so. Less than the thickness of a sheet of paper which is .003". 
I ran two pieces of rough sawn red oak through it, both flat and edge.  Now both pieces fit together perfectly. Edge to edge when held up to the sun I see no light leaking through.  Face to face they make a sucking sound when I pull them apart. It also is not making wedges.  Measurments before and after show the same amount is being taken off edge to edge and end to end.
Thank you for your help.  I may contact you again when I start setting up my thickness planer. I have never used one and I can find no information on this one.  It is a United 15"  made by Newcorp.  The only other info I have from the name plate is it is a model number 407. Imported from Taiwan.  Newport was out of Las Vegas, NV.  The date on the motor ID plate is 1984. It is a 2 hp.
Thanks again,
Jerry B.

From jamescrombie at jamescrombie.com  Tue Apr  7 06:59:04 2009
From: jamescrombie at jamescrombie.com (James P Crombie)
Date: Mon, 06 Apr 2009 17:59:04 -0400
Subject: [ATM] Woodworking help needed
In-Reply-To: <545698.71564.qm@web180101.mail.gq1.yahoo.com>
References: <545698.71564.qm@web180101.mail.gq1.yahoo.com>
Message-ID: <49DA7B28.4050204@jamescrombie.com>

Jerry Hillman wrote:
> To all the Master Woodworkers on the list,
> I have seen some of the absolutely beautiful work some of you have done. I need a little help.
> I just acquired a 6" planer/jointer from my step-dad. Amoung other things I want to use this to build a nice telescope mount for my 10" and my 15". I have gradually been getting the tools together to start a woodworking business since I can no longer drive a truck, or drive at all.
> I have cleaned this tool, removed all the rust from the table and fence, removed, cleaned, and sharpened the blades and put it all back together according to the owners manual instructions. It is made by Craftsman so that tells something else about it. It creates wedges when I run boards through it. What is wrong?
> Jerry B
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>
>
>   
There a couple of web pages on setting up a jointer.  Here are a few of them

http://www.woodworkweb.com/index.php?option=com_content&task=view&id=64&Itemid=37

this has a video about half way down
http://www.newwoodworker.com/usejntr.html

http://woodgears.ca/jointer/knives.html

From wkitty42 at windstream.net  Tue Apr  7 08:18:44 2009
From: wkitty42 at windstream.net (waldo kitty)
Date: Mon, 06 Apr 2009 19:18:44 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <1184829206.20090406174613@foucault.co.uk>
References: <1403544071.20090406162415@foucault.co.uk>	<Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<1184829206.20090406174613@foucault.co.uk>
Message-ID: <49DA8DD4.401@windstream.net>

Richard in the UK wrote:
> Hello Dominic-Luc,
> 
> Monday, April 6, 2009, 5:28:09 PM, you wrote:
> 
>> Could you be mixing (pardon the pun) cement and grout?
>> >From Wikipedia:
> 
> No, I never heard of sand in grout.

me either... to me, grout is almost the same as plaster with the obvious (lack 
of) water absorbing properties...

-- 
NOTE: NEW EMAIL ADDRESS!!

        _\/
       (@@)                      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 camkit at mweb.co.za  Tue Apr  7 09:25:54 2009
From: camkit at mweb.co.za (chris forder)
Date: Tue, 07 Apr 2009 02:25:54 +0200
Subject: [ATM] please ID this tile tool material
Message-ID: <49DA9D92.2010609@mweb.co.za>

I use grout (cement & water) to make my tools. I cast them on the mirror 
surface - using cling wrap as a separator, and, after they have 
solidified, I put them in water for a few weeks. When it finally cures, 
it rings like china. I have had some of these tools for up to 10 years 
and have had no deterioration. Once dry, I paint the surface with resin, 
allow to dry and then resin the tiles onto the pre curved surface (or 
use it for the pitch lap foundation if I am making a polishing tool).

Chris
Cape Town


From b-hamburger at ya.com  Tue Apr  7 17:09:53 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Tue, 7 Apr 2009 10:09:53 +0200
Subject: [ATM] ATM: Re: Please ID this tile tool material-
In-Reply-To: <5A6860DBA6514E139059DDFB21534D88@R101>
References: <5A6860DBA6514E139059DDFB21534D88@R101>
Message-ID: <00a801c9b758$3ce27950$b6a76bf0$@com>

To confuse matters a Little more, there is a big variety of dental plasters, stones, model stones etc. Have a look at http://www.protechno.es/en/productos.php?f=1&t=4

The good news is there is also a big difference in price. I just ordered Durguix model stone and paid for a 20kg bucket 30? while "dental plaster" would sell for twice the price. More so, I expect the stone to be harder and more apt to our application.

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 stainless_steel at suddenlink.net
> Sent: viernes, 03 de abril de 2009 0:08
> To: ATM list
> Subject: [ATM] ATM: Re: Please ID this tile tool material-
> 
> 
> As I mentioned in this august forum ages ago, I once read where an
> accomplisheed ATM said, in print in a regular publication: "Dental Stone
> is
> not dimensionally stable." Hence, my mostly silica based base for the hex
> tiles in this article:
> 
> http://www.atmsite.org/contrib/Harbour/Tool.html
> 
> DLZ-130
> 
> 
> >Hi,
> 
> >Another remark about dental Stone:
> >I cannot remember the brand I used to use earlier and found one locally
> >called GC base stone. However it turns out to be tixotropic (becomes
> >viscous
> >under pressure), so I did not buy it. A little research showed that quite
> a
> >few dental stones show that property, so I guess it would be advisable to
> >ask before you buy.
> 
> >Berthold
> 
> --
> Berthold Hamburger - Cellist/Spain
> Email: behambu at artinso.com
> http://www.artinso.com
> http://www.astro.artinso.com
> 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From nilsolof.carlin at telia.com  Tue Apr  7 19:00:39 2009
From: nilsolof.carlin at telia.com (Nils Olof Carlin)
Date: Tue, 7 Apr 2009 12:00:39 +0200 (CEST)
Subject: [ATM] please ID this tile tool material
Message-ID: <17585428.167621239098439089.JavaMail.defaultUser@defaultHost>

Dominic,

for the very few tools I have made, I used a mixture of the powder 
(called "Portland cement" on the bag) and water, with no other 
additives. It has worked for me (and at least one still in existence 
after several years has not cracked). Luckily, I have not had to worry 
about the correct addressing of the mixture ;-) . When hardened, it is 
about as soft/hard as limestone - and I could cut shallow channels 
between the tiles with a dremel-like grinder, it helped greatly with 
the even distribution of carbo.


 But maybe I will try some quicker stuff next time (if one).

Nils Olof

From stainless_steel at suddenlink.net  Tue Apr  7 22:44:15 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Tue, 7 Apr 2009 08:44:15 -0500
Subject: [ATM] ATM: Re: Please ID this tile tool material-
Message-ID: <30F6CC3960C14C8A9B0E34BD98A39BE3@R101>

Tom has described essentially what I have described in detail here:

http://www.atmsite.org/contrib/Harbour/Tool.html

I made many of these, never had a piece of sand fall out on the workpieces.

Easy to make; avoid mistakes by reading the article (I have learned how to 
avoid the mistakes I made at first in the construction of this rypew of tool 
for finishing already curve generated mirrors- almost exclusively all twelve 
and half inch blanks-)

Even tho epoxy will work, if you epoxy the tiles on the tool, if you finish 
your mirror in a timely way, it is dimensionally unstable over time, and not 
necessary for attaching the tiles. Read my method in the article. I had a 
tool and the fine ground blank I used it on to fine grind it again- 15 years 
later, the tool still fit perfectly flush with the curve on the mirror.

DLZ-130


>I agree, trade names are regional.

>Without something to bind with, 100% cement is no good. One part cement,
>two parts sharp sand mixed as lean as possible with water (but a
>cohesive mixture). Allow to hydrate (keep moist) about 28 days for good
>compressive strength. Oven dry it ~150-175F. Epoxy seal it. Epoxy the
>tiles. A cheap tool is born.

>There are many suitable materials to make a tile tool with. Recently I
>used a 6" tool to hog and fine grind an 8" f/6 to f/4.0. The 6" tool was
>a 0.375" thick piece of A36 steel and the tiles were held with pitch.
>The pitch was very hard and poured thin (~1/16"). Placed in cool water.
>The channels were not fully cut to the steel. It took about ~45 minutes
>to have a tile tool up and running on the Mirror-Matic.

>Tom Polk



From rmay at nethere.com  Wed Apr  8 06:19:14 2009
From: rmay at nethere.com (Bob May)
Date: Tue, 7 Apr 2009 14:19:14 -0700
Subject: [ATM] please ID this tile tool material
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
Message-ID: <000b01c9b7c6$81cbe240$8f78fea9@amd>

Cheapest tool that I've done is Hydrocal (price on that is about
the same as cement) and glass for the tiles.  $30 for a 90lb. bag
of Hydrocal and a bumch of glass from the back of a glass shop of
1/4" thickness and some time cutting it up and making the tool.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From b-hamburger at ya.com  Wed Apr  8 06:27:29 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Tue, 7 Apr 2009 23:27:29 +0200
Subject: [ATM] please ID this tile tool material
In-Reply-To: <000b01c9b7c6$81cbe240$8f78fea9@amd>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
Message-ID: <002c01c9b7c7$a8767440$f9635cc0$@com>

Hi,

I have a general question regarding the hole tool issue and ask you to bear
with me, as this has certainly popped up many times over the years.

The issue is, that I have been absent from ATM for some years. I did my last
mirror 12 years ago and at that time general wisdom dictated that you would
cast the tool and then epoxy the tiles on. That's how I ever did it.

However, I am under the impression that now most people just cast the tool
around the tiles and I am wondering how that came to be? Clearly grinding
the tiles down will also grind off plaster which in turn will scratch your
glass. At least that is what I would imagine. As a matter of fact, I used to
seal my dental plaster tools to avoid having plaster come off.

Could someone enlighten me briefly about that "new" technique?

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 Bob May
> Sent: martes, 07 de abril de 2009 23:19
> To: atm at atmlist.net
> Subject: Re: [ATM] please ID this tile tool material
> 
> Cheapest tool that I've done is Hydrocal (price on that is about
> the same as cement) and glass for the tiles.  $30 for a 90lb. bag
> of Hydrocal and a bumch of glass from the back of a glass shop of
> 1/4" thickness and some time cutting it up and making the tool.
> 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 Apr  8 06:42:27 2009
From: atmpob at yahoo.com (Dale Eason)
Date: Tue, 7 Apr 2009 14:42:27 -0700 (PDT)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <002c01c9b7c7$a8767440$f9635cc0$@com>
Message-ID: <708206.53211.qm@web54502.mail.re2.yahoo.com>



http://gotgrit.com/make_tool1.php

--- On Tue, 4/7/09, Berthold Hamburger <b-hamburger at ya.com> wrote:

> From: Berthold Hamburger <b-hamburger at ya.com>
> Subject: Re: [ATM] please ID this tile tool material
> To: atm at atmlist.net
> Date: Tuesday, April 7, 2009, 4:27 PM
> Hi,
> 
> I have a general question regarding the hole tool issue and
> ask you to bear
> with me, as this has certainly popped up many times over
> the years.
> 
> The issue is, that I have been absent from ATM for some
> years. I did my last
> mirror 12 years ago and at that time general wisdom
> dictated that you would
> cast the tool and then epoxy the tiles on. That's how I
> ever did it.
> 
> However, I am under the impression that now most people
> just cast the tool
> around the tiles and I am wondering how that came to be?
> Clearly grinding
> the tiles down will also grind off plaster which in turn
> will scratch your
> glass. At least that is what I would imagine. As a matter
> of fact, I used to
> seal my dental plaster tools to avoid having plaster come
> off.
> 
> Could someone enlighten me briefly about that
> "new" technique?
> 
> 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 Bob May
> > Sent: martes, 07 de abril de 2009 23:19
> > To: atm at atmlist.net
> > Subject: Re: [ATM] please ID this tile tool material
> > 
> > Cheapest tool that I've done is Hydrocal (price on
> that is about
> > the same as cement) and glass for the tiles.  $30 for
> a 90lb. bag
> > of Hydrocal and a bumch of glass from the back of a
> glass shop of
> > 1/4" thickness and some time cutting it up and
> making the tool.
> > 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 holmmarkd at gmail.com  Wed Apr  8 10:31:46 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Tue, 07 Apr 2009 21:31:46 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <002c01c9b7c7$a8767440$f9635cc0$@com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
Message-ID: <49DBFE82.2090300@gmail.com>

Part of the answer is using a water resistant grade of plaster.  This is 
the main reason we push dental stone and Hydrostone.  They are also 
stronger than most other plasters.  With a water resistant plaster, you 
don't need to seal to protect the plaster.

The other part of the answer is to use mats of tile.  These are 
manufactured for the convenience of the tile layer.  He/she can place a 
square foot of tile at a time, instead of a square inch.  In our case, 
not only does the mat space the tiles, it also holds them in position 
while we pour the plaster on their back.  We want the plaster to flow 
down between the tiles in order to set around them and grip them firmly 
in place.  A couple of healthy bangs of the stack against the table top 
are usually recommended to help make sure the plaster gets between the 
tiles.

Another trick is to poke through the plaster with a thin implement to 
make sure the tiles are not floating up.  A very clever atm suggested 
that bamboo teriyaki skewers found at grocery stores work very well for 
this job and won't risk scratching glass.

There is no problem from scratching using true plaster products.  The 
plaster is much softer than both glass, and the abrasive, so it just 
grinds to dust and doesn't cause any scratches.  To a certain extent, 
the tool is self channeling, because the plaster wears faster than the 
tiles.  The plaster between the tiles will always wear a bit deeper than 
the tiles themselves, even without specific intervention.

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From dlwebb at canit.se  Wed Apr  8 19:00:40 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Wed, 8 Apr 2009 12:00:40 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <002c01c9b7c7$a8767440$f9635cc0$@com>
Message-ID: <Pine.LNX.4.44.0904081144590.6311-100000@uno.canit.se>

On Tue, 7 Apr 2009, Berthold Hamburger wrote:

> the tiles down will also grind off plaster which in turn will scratch your
> glass. At least that is what I would imagine. As a matter of fact, I used to
> seal my dental plaster tools to avoid having plaster come off.
>
> Could someone enlighten me briefly about that "new" technique?
>
> Berthold

I would immediately get scolded by several people at least for
some of my practices that have worked extremely well in my
hands. Have a look at the tile tool I used for my 310 mm
F/1.55 mirror. That mirror has not a single scratch or pit
that I can find anywhere on the entire surface.

This concrete tool is made from common concrete with sand
and gravel. Thin plastic was placed over mirror surface,
tiles set in position and concrete poured with no effort
to create channels. Mirror surface saw direct contact with
both concrete and tile during all stages of grinding. Lots
of rocks and sand, even big chips on edges, no channels,
and no scratches:

http://www.canit.se/~dlwebb/catadioptric/310schmidt/grindtool.jpg
http://www.canit.se/~dlwebb/catadioptric/310schmidt/grindtool_edge.jpg

Dominic



From mjc5 at psu.edu  Wed Apr  8 22:31:30 2009
From: mjc5 at psu.edu (Michael Coslo)
Date: Wed, 08 Apr 2009 09:31:30 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <Pine.LNX.4.44.0904081144590.6311-100000@uno.canit.se>
References: <Pine.LNX.4.44.0904081144590.6311-100000@uno.canit.se>
Message-ID: <E6B7CBC5-B1EC-402B-859C-EBBA8BC8A31A@psu.edu>


On Apr 8, 2009, at 6:00 AM, Dominic-Luc Webb wrote:

> On Tue, 7 Apr 2009, Berthold Hamburger wrote:
>
>> the tiles down will also grind off plaster which in turn will  
>> scratch your
>> glass. At least that is what I would imagine. As a matter of fact,  
>> I used to
>> seal my dental plaster tools to avoid having plaster come off.
>>
>> Could someone enlighten me briefly about that "new" technique?
>>
>> Berthold
>
> I would immediately get scolded by several people at least for
> some of my practices that have worked extremely well in my
> hands. Have a look at the tile tool I used for my 310 mm
> F/1.55 mirror. That mirror has not a single scratch or pit
> that I can find anywhere on the entire surface.
>
> This concrete tool is made from common concrete with sand
> and gravel. Thin plastic was placed over mirror surface,
> tiles set in position and concrete poured with no effort
> to create channels. Mirror surface saw direct contact with
> both concrete and tile during all stages of grinding. Lots
> of rocks and sand, even big chips on edges, no channels,
> and no scratches:


I'm with you there.

I have a tool - a 12 inch stepping stone, made of concrete, with metal  
washers epoxied to it. It probably represents the bottom end of the  
expense scale, I think it cost less than ten dollars to make. On the  
other end of that scale, my first mirror, a 12.5 inch, had a tool made  
of another 12.5 inch blank, possibly representing the other end of the  
expense spectrum. I wouldn't have used the other blank, but when I  
bought them, the mirror was partially ground already. Another is  
porcelain tiles on a plaster and wood base, with some of Richard's  
famous sauce.

I look at grinding tools as a minor art forms, not to get too spun up  
about. Everyone has something that will work - more or less.

My only concerns have been the use of flat tiles after hogging out  
with another tool. It seems to me that in that case, you almost have  
to do a casting with the tiles in place. Since you'll have these nice  
new tiles which are flat, when in fact you want them to have some  
radius to them. Seems to me that if you just lay them on a flat tool,  
it will be pretty rough going for a bit until the tool gets seated.  
Even a tool where the tiles are cast into the plaster, where the angle  
can be approximated, will be grinding on the corners of the tiles for  
a good bit.

Which is why my favorite of the three tools I mentioned was the  
porcelain tile on plaster and wood base. It was used the whole way  
through, from hogging to fine grinding, with none of the hassle of  
seating a new tool. Those hard tiles were excellent. Tough as nails,  
and they worked a trick. Not a chip or scratch during the whole grind.  
Intangible was that it simply felt nice and smooth from start to  
finish.  Only thing I would note is that you have to be very careful,  
as the tiles eventually get extremely sharp edges. They don't hurt the  
mirror, but cut fingers like a scalpel.


-73 de Mike N3LI -



From dlwebb at canit.se  Wed Apr  8 23:11:55 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Wed, 8 Apr 2009 16:11:55 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <E6B7CBC5-B1EC-402B-859C-EBBA8BC8A31A@psu.edu>
Message-ID: <Pine.LNX.4.44.0904081555530.21521-100000@uno.canit.se>

On Wed, 8 Apr 2009, Michael Coslo wrote:
>
> I look at grinding tools as a minor art forms, not to get too spun up
> about. Everyone has something that will work - more or less.
>


Ahh right, so you were the one with the metal washers. I have
seen pics of one such tool. I guess it was yours? Art is
exactly what this is to me and I have some real beauties!
Most of my tool creations (just can't conceive of calling
these inventions) have no particular technical worth more
than pushing down the price of a tool to ridiculous lows. By
any standard of mirror making norms, I have repeatedly and
without remorse slapped the face of ATM decency. Miraculously,
most of my fine art has worked great no matter what I have
done.

I have a lot of "undocumented" tools, and suspect I am not
alone. At some point we really should think about a tool
art exhibit, presumably online. Collectively, we could
probably fill a museum.

Dominic


From pdebaan at hotmail.com  Thu Apr  9 01:45:41 2009
From: pdebaan at hotmail.com (Peter De Baan)
Date: Wed, 8 Apr 2009 16:45:41 +0000
Subject: [ATM] please ID this tile tool material
In-Reply-To: <E6B7CBC5-B1EC-402B-859C-EBBA8BC8A31A@psu.edu>
References: <Pine.LNX.4.44.0904081144590.6311-100000@uno.canit.se>
	<E6B7CBC5-B1EC-402B-859C-EBBA8BC8A31A@psu.edu>
Message-ID: <BLU137-W14E324E3911BD53504FAB3B2820@phx.gbl>



 


> I look at grinding tools as a minor art forms, not to get too spun up 
> about. Everyone has something that will work - more or less.
 
> Which is why my favorite of the three tools I mentioned was the 
> porcelain tile on plaster and wood base. It was used the whole way 
> through, from hogging to fine grinding, with none of the hassle of 
> seating a new tool. Those hard tiles were excellent. Tough as nails, 
> and they worked a trick. Not a chip or scratch during the whole grind. 
> Intangible was that it simply felt nice and smooth from start to 
> finish. Only thing I would note is that you have to be very careful, 
> as the tiles eventually get extremely sharp edges. They don't hurt the 
> mirror, but cut fingers like a scalpel.
> -73 de Mike N3LI -

 

Everyone has something that will work - more or less.

To avoid the danger of cutting your fingers in the tile edge, and shorten 

your hogging time: hold off on making your tile tool, until you are done

with hogging, do the hogging with a simple steel/galvanised pipe cap of

2 to 3" diameter (which hardly wear down and can be used over and over)

and grind with the same grit as the tile tool but much faster (weigh it down

with 5 lb) and less tiresome and no finger cutting danger 

 

Peter

 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


_________________________________________________________________
Quick access to your favorite MSN content and Windows Live with Internet Explorer 8. 
http://ie8.msn.com/microsoft/internet-explorer-8/en-us/ie8.aspx?ocid=B037MSN55C0701A

From rmay at nethere.com  Thu Apr  9 05:44:23 2009
From: rmay at nethere.com (Bob May)
Date: Wed, 8 Apr 2009 13:44:23 -0700
Subject: [ATM] please ID this tile tool material
References: <Pine.LNX.4.44.0904081144590.6311-100000@uno.canit.se>
	<E6B7CBC5-B1EC-402B-859C-EBBA8BC8A31A@psu.edu>
Message-ID: <001201c9b88a$cddd4d80$8f78fea9@amd>

I find that metal of any kind grinds too slowly (the metal, not
the glass) to convorm to the shape of the mirror.
As to grinding with "flat tiles", I'll start a slumped glass at
320 grit and three wets get a full curve of the mirror on the
tile tool with no problems.  The differnce between a flat and the
mirror curvature is very small for a 1" tile.
Epoxy isn't really needed as the plaster does a decent job of
holding the tiles (or glass) without any problems.  The basic
intent here is to make a tool in short order and start using it.
If you do plan on using glass for the tiles, either cut the glass
for the tiles with a tile saw or, when cracking them, put the
glass down so that the wide part is away from the mirror so it is
well held in the plaster.  As far as I am concerned, if it takes
more than a half hour to make a tool and start grinding again, it
has taken too long!
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Thu Apr  9 05:51:53 2009
From: rmay at nethere.com (Bob May)
Date: Wed, 8 Apr 2009 13:51:53 -0700
Subject: [ATM] please ID this tile tool material
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
Message-ID: <001901c9b88b$e2ccb040$8f78fea9@amd>

I'm afraid that I'm one of the persons putting forth the tile
tool idea.
I'm CHEAP!
The idea of usiong another piece of glass to grind a mirror is
just a big waste of material.  I'd rather use it to make another
mirror.
Got the idea of using floor tiles from somebody else and promptly
started thinking of how inexpensive that it could become.  The
idea of using epoxy (what kind was my first question and the boat
epoxy paint didn't come to mind) seemed to be a waste of
expensive 5 minute epoxy so I just put the tiles in the plaster.
The other thing was that I had a source of a fair bit of dental
stone so that is what I used in the beginning.  25lb. of dental
stone makes a fair number of tools to the point where the tiles
were actually the more expensive part of the tool.  Lately, floor
tiles have become hard to find locally so I've started using
thick glass from anywhere.
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 Apr  9 06:07:19 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Wed, 8 Apr 2009 16:07:19 -0500
Subject: [ATM] ATM: Re: Can someone ID this too material?
Message-ID: <092BCBCB3DDF4D41B89ADF7E7B493643@R101>

Berthold,

I address that issue in detail in my article, as I said. Go here to see how 
I ensure that the tiles do not come off:

http://www.atmsite.org/contrib/Harbour/Tool.html

(the channels are waxed; the wax serves four purposes: it seals the sand 
away from the bottom of the channels;  the wax is excavated to a one thirty 
secondth of an inch, to help with slurry distribution;  it helps hold the 
tiles on; it traps a rogue grit if one gets in there despite your best 
efforts to keep it off the tool)- yes, the tiles are emplaced before the mix 
is poured onto the tool. Read about it in detail at the atm site. The tiles 
are gripped to halfway up. If you are starting from flat, and hogging out, 
they will indeed wear down near the edge before you can finish; in this 
case, you are forced to re-tile, and have to use epoxy. In that case, you 
will want to finish in a timely way. Don't put the mirror and tool up for an 
extended period of time, as epoxy is not dimensionally stable, and the tiles 
will migrate, unevenly, upwards.

This is not hearsay. I learned this the hard way.

DLZ-130

>Hi,

>I have a general question regarding the hole tool issue and ask you to bear
>with me, as this has certainly popped up many times over the years.
>The issue is, that I have been absent from ATM for some years. I did my 
>last
>mirror 12 years ago and at that time general wisdom dictated that you would
>cast the tool and then epoxy the tiles on. That's how I ever did it.

>However, I am under the impression that now most people just cast the tool
>around the tiles and I am wondering how that came to be? Clearly grinding
>the tiles down will also grind off plaster which in turn will scratch your
>glass. At least that is what I would imagine. As a matter of fact, I used 
>to
>seal my dental plaster tools to avoid having plaster come off.

>Could someone enlighten me briefly about that "new" technique?

>Berthold


From holmmarkd at gmail.com  Thu Apr  9 09:35:10 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Wed, 08 Apr 2009 20:35:10 -0400
Subject: [ATM] My take on the whole tool thing. was Re: please ID this tile
 tool material
In-Reply-To: <001901c9b88b$e2ccb040$8f78fea9@amd>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<001901c9b88b$e2ccb040$8f78fea9@amd>
Message-ID: <49DD42BE.8020000@gmail.com>

I've been following these tool making discussions / arguments for 
several years now on this list, and have come to a few conclusions:

1.  There are several methods that work.

2.  The best tool construction does depend a bit on what you are going 
to do with the tool:  metal facing is probably best for roughing hard 
glass, etc.

3. Bob May has the most convincing case for the "best" way to make a 
tool for fine grinding a pre-roughed blank.  Bob's method is quite 
similar to that described by Richard Schwartz and quite similar to the 
method outlined at gotgrit.com.  Many very active (read: have made a 
bunch of mirrors) atm's use this method or slight variations on it.

4. Historically, the tile-epoxy-plaster tool came first.  It does work, 
but takes more time and money. Bob is right.  Epoxy is expensive.  The 
big time waster is that the plaster has to dry before epoxy will stick.  
As Bob pointedly reminds us, tile-in-stone tools can go from a pile of 
raw materials to fine grinding in under an hour.  You don't even get an 
excuse for a coffee break.  I don't think anybody beats that yet.

5. There may be parts of the world where dental stone or a Hydrostone 
like product are not available.  For those places, portland cement based 
products are more likely to be available, and will work.  There are also 
guys that won't buy anything that can't be bought at the local home 
center.  (Real reason: they can't stay away from the displays of 
gigantic, brushed stainless steel gas grills and turbocharged lawn 
tractors.)  For them, portland cement is the only available option.  I'd 
recommend Dave Harbour's methods for a cement based tool, just because I 
know he is an awfully practical fellow who only passes on tried and true 
knowledge.

6. Although portland cement based products appear to work out fine, I'll 
still recommend dental stone / Hydrostone as the first choice.  Among 
other things, on the few occasions I have worked portland cement 
products by hand, I have taken off a fair amount of skin.  That stuff is 
too alkaline for my hands.  Dental stone is chemically gentle to my 
skin, but sticks tenaciously to the hair on the back of my hands.  Ouch!

7.  I'd avoid anything involving wood or a wood product (except as a 
form).  This isn't the place for it.

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From dlwebb at canit.se  Thu Apr  9 16:58:03 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Thu, 9 Apr 2009 09:58:03 +0200 (MET DST)
Subject: [ATM] please ID this tile tool material
In-Reply-To: <001201c9b88a$cddd4d80$8f78fea9@amd>
Message-ID: <Pine.LNX.4.44.0904090941120.16007-100000@uno.canit.se>

On Wed, 8 Apr 2009, Bob May wrote:

> well held in the plaster.  As far as I am concerned, if it takes
> more than a half hour to make a tool and start grinding again, it
> has taken too long!
> Bob May

This is where my concrete tools might lose to other materials,
if there are other choices. Not so in my case, but as per my
initial posting, I did once obtain what is now clearly a
hydrostone tool. I got that when in California. I should make
clear that I rather like this hydrostone material, but normally
use concrete with success. I will buy some hydrostone next
trip to USA (May or June???), due to interest, not necessity.

Dominic


From b-hamburger at ya.com  Thu Apr  9 18:50:23 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Thu, 9 Apr 2009 11:50:23 +0200
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <49DD42BE.8020000@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
Message-ID: <009d01c9b8f8$9bdf6980$d39e3c80$@com>

Thank you all for the good comments. I just received a new supply of dental
stone and will put it all in  practice!

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 Mark Holm
> Sent: jueves, 09 de abril de 2009 2:35
> To: atm at atmlist.net
> Subject: [ATM] My take on the whole tool thing. was Re: please ID this
> tile tool material
> 
> I've been following these tool making discussions / arguments for
> several years now on this list, and have come to a few conclusions:
> 
> 1.  There are several methods that work.
> 
> 2.  The best tool construction does depend a bit on what you are going
> to do with the tool:  metal facing is probably best for roughing hard
> glass, etc.
> 
> 3. Bob May has the most convincing case for the "best" way to make a
> tool for fine grinding a pre-roughed blank.  Bob's method is quite
> similar to that described by Richard Schwartz and quite similar to the
> method outlined at gotgrit.com.  Many very active (read: have made a
> bunch of mirrors) atm's use this method or slight variations on it.
> 
> 4. Historically, the tile-epoxy-plaster tool came first.  It does work,
> but takes more time and money. Bob is right.  Epoxy is expensive.  The
> big time waster is that the plaster has to dry before epoxy will stick.
> As Bob pointedly reminds us, tile-in-stone tools can go from a pile of
> raw materials to fine grinding in under an hour.  You don't even get an
> excuse for a coffee break.  I don't think anybody beats that yet.
> 
> 5. There may be parts of the world where dental stone or a Hydrostone
> like product are not available.  For those places, portland cement based
> products are more likely to be available, and will work.  There are also
> guys that won't buy anything that can't be bought at the local home
> center.  (Real reason: they can't stay away from the displays of
> gigantic, brushed stainless steel gas grills and turbocharged lawn
> tractors.)  For them, portland cement is the only available option.  I'd
> recommend Dave Harbour's methods for a cement based tool, just because I
> know he is an awfully practical fellow who only passes on tried and true
> knowledge.
> 
> 6. Although portland cement based products appear to work out fine, I'll
> still recommend dental stone / Hydrostone as the first choice.  Among
> other things, on the few occasions I have worked portland cement
> products by hand, I have taken off a fair amount of skin.  That stuff is
> too alkaline for my hands.  Dental stone is chemically gentle to my
> skin, but sticks tenaciously to the hair on the back of my hands.  Ouch!
> 
> 7.  I'd avoid anything involving wood or a wood product (except as a
> form).  This isn't the place for it.
> 
> --
> Mark Holm
> markholm at verizon.net
> holmmarkd at gmail.com
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From richard at foucault.co.uk  Thu Apr  9 18:50:45 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Thu, 9 Apr 2009 10:50:45 +0100
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <49DD42BE.8020000@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<001901c9b88b$e2ccb040$8f78fea9@amd> <49DD42BE.8020000@gmail.com>
Message-ID: <639227953.20090409105045@foucault.co.uk>

Hello Mark,

Thursday, April 9, 2009, 1:35:10 AM, you wrote:

> 5. There may be parts of the world where dental stone or a Hydrostone 
> like product are not available.

In the case of Hydrostone I think that will be anywhere other than the
USA. The economies of those sorts of products just don't lend
themselves to export. It would be very useful for those of us that
live in the ROW if people could try to use generic names (like dental
plaster) rather than trade names (like Hydrostone).

BTW, is Bob's method written up anywhere please?

-- 
Best regards,
 Richard in the UK


From b-hamburger at ya.com  Thu Apr  9 19:19:50 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Thu, 9 Apr 2009 12:19:50 +0200
Subject: [ATM] My take on the whole tool thing. was Re: please ID
	this	tile tool material
In-Reply-To: <639227953.20090409105045@foucault.co.uk>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
	<639227953.20090409105045@foucault.co.uk>
Message-ID: <009e01c9b8fc$ba83a9b0$2f8afd10$@com>

If you live in Europe you can have a look for example at
http://www.protechno.es/en/productos.php?f=1 and then look for a local
distributor. There are however many brands available and can usually found
at dental supply mailorder outlets.

Berthold

-- 
Berthold Hamburger - Cellist/Spain
Email: behambu at artinso.com
http://www.artinso.com
http://www.astro.artinso.com


> -----Original Message-----
> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf
> Of Richard in the UK
> Sent: jueves, 09 de abril de 2009 11:51
> To: Mark Holm
> Subject: Re: [ATM] My take on the whole tool thing. was Re: please ID
> this tile tool material
> 
> Hello Mark,
> 
> Thursday, April 9, 2009, 1:35:10 AM, you wrote:
> 
> > 5. There may be parts of the world where dental stone or a Hydrostone
> > like product are not available.
> 
> In the case of Hydrostone I think that will be anywhere other than the
> USA. The economies of those sorts of products just don't lend
> themselves to export. It would be very useful for those of us that
> live in the ROW if people could try to use generic names (like dental
> plaster) rather than trade names (like Hydrostone).
> 
> BTW, is Bob's method written up anywhere please?
> 
> --
> Best regards,
>  Richard in the UK
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From dlwebb at canit.se  Thu Apr  9 19:37:57 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Thu, 9 Apr 2009 12:37:57 +0200 (MET DST)
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <639227953.20090409105045@foucault.co.uk>
Message-ID: <Pine.LNX.4.44.0904091216340.11479-100000@uno.canit.se>

On Thu, 9 Apr 2009, Richard in the UK wrote:

> live in the ROW if people could try to use generic names (like dental
> plaster) rather than trade names (like Hydrostone).

Please note that Hydrostone is sold separately and
distinguished from dental plaster according to physical
properties, like consistency. Specifically, please see
page 54-55 of the Claypeople catalog:

http://claypeople.net/images/claypeoplecatalog.pdf


Clearly we can use either and should specify what the
trade names are. When I posted, I didn't know what
material my tool was. Then I learned it is likely
Hydrostone. Then I learned Hydrostone is type of plaster,
similar to dental plaster. Then I learned people who are
specialists in plaster discern between hydrostone and
dental stone.

I suppose we could have called it plaster, but as I
initially posted, my tool does not look or feel like
usual plaster (including dental plaster), and seems
generally superior. The point of my post was actually
to be very specific, not generic.


Dominic


From richard at foucault.co.uk  Thu Apr  9 19:50:15 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Thu, 9 Apr 2009 11:50:15 +0100
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <Pine.LNX.4.44.0904091216340.11479-100000@uno.canit.se>
References: <639227953.20090409105045@foucault.co.uk>
	<Pine.LNX.4.44.0904091216340.11479-100000@uno.canit.se>
Message-ID: <75161501.20090409115015@foucault.co.uk>

Hello Dominic-Luc,

Thursday, April 9, 2009, 11:37:57 AM, you wrote:

> Please note that Hydrostone is sold separately and
> distinguished from dental plaster according to physical
> properties, like consistency.

Sure it is, but what relevance is it to you in Sweden and me in the
UK, as it is not available?

-- 
Best regards,
 Richard in the UK


From dlwebb at canit.se  Thu Apr  9 19:58:55 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Thu, 9 Apr 2009 12:58:55 +0200 (MET DST)
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <75161501.20090409115015@foucault.co.uk>
Message-ID: <Pine.LNX.4.44.0904091257500.19077-100000@uno.canit.se>

On Thu, 9 Apr 2009, Richard in the UK wrote:
>
> Sure it is, but what relevance is it to you in Sweden...
> --
> Best regards,
>  Richard in the UK


Understood. I am buying some next month in the States.

Dominic


From richard at foucault.co.uk  Thu Apr  9 20:46:31 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Thu, 9 Apr 2009 12:46:31 +0100
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <Pine.LNX.4.44.0904091257500.19077-100000@uno.canit.se>
References: <75161501.20090409115015@foucault.co.uk>
	<Pine.LNX.4.44.0904091257500.19077-100000@uno.canit.se>
Message-ID: <1656458916.20090409124631@foucault.co.uk>

Hello Dominic-Luc,

Thursday, April 9, 2009, 11:58:55 AM, you wrote:

> I am buying some next month in the States.

Why not use a local equivalent product?

-- 
Best regards,
 Richard in the UK


From dlwebb at canit.se  Thu Apr  9 21:01:08 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Thu, 9 Apr 2009 14:01:08 +0200 (MET DST)
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <1656458916.20090409124631@foucault.co.uk>
Message-ID: <Pine.LNX.4.44.0904091353050.29059-100000@uno.canit.se>

On Thu, 9 Apr 2009, Richard in the UK wrote:

> > I am buying some next month in the States.
>
> Why not use a local equivalent product?

Now that I know what it is, that is indeed possible. My
understanding is that "Hydrostone" is currently product
name of the large international company, USG (US Gypsum).
USG had offices throughout EU just a few years ago,
including very near my home near Stockholm.

Dominic


From mjc5 at psu.edu  Thu Apr  9 21:12:12 2009
From: mjc5 at psu.edu (Michael Coslo)
Date: Thu, 09 Apr 2009 08:12:12 -0400
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <49DD42BE.8020000@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<001901c9b88b$e2ccb040$8f78fea9@amd> <49DD42BE.8020000@gmail.com>
Message-ID: <A70954BB-6D06-4C23-A661-4430F49164BD@psu.edu>


On Apr 8, 2009, at 8:35 PM, Mark Holm wrote:
>
> 6. Although portland cement based products appear to work out fine,  
> I'll still recommend dental stone / Hydrostone as the first choice.   
> Among other things, on the few occasions I have worked portland  
> cement products by hand, I have taken off a fair amount of skin.   
> That stuff is too alkaline for my hands.  Dental stone is chemically  
> gentle to my skin, but sticks tenaciously to the hair on the back of  
> my hands.  Ouch!
>
> 7.  I'd avoid anything involving wood or a wood product (except as a  
> form).  This isn't the place for it.

Hi Mark,

I have to respectfully disagree about the wood part. I'll guess that  
your dislike is about the wood and wetness aspect. But a wood form  
backing a plaster tool makes for a very nice tool platform. Wood,  
especially plywood,  has properties that complement those of plaster,  
or other cured stonelike materials. It would also keep the portland  
cement away from your skin.



  side note - portland cement is really, really caustic and is a great  
way to mess up your skin in general. Wear gloves.

-73 de Mike N3LI -



From mjc5 at psu.edu  Fri Apr 10 00:43:14 2009
From: mjc5 at psu.edu (Michael Coslo)
Date: Thu, 09 Apr 2009 11:43:14 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <001901c9b88b$e2ccb040$8f78fea9@amd>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<001901c9b88b$e2ccb040$8f78fea9@amd>
Message-ID: <88E57575-631F-4519-A3F5-210C7BA4BABD@psu.edu>


On Apr 8, 2009, at 4:51 PM, Bob May wrote:

> I'm afraid that I'm one of the persons putting forth the tile
> tool idea.
> I'm CHEAP!
> The idea of usiong another piece of glass to grind a mirror is
> just a big waste of material.  I'd rather use it to make another
> mirror.

No argument there, Bob. When I used another blank to do my mirror, it  
was already hogged with the glass blank. So I figured I might as well  
use it. Along the way I learned a lot about why a solid tool isn't as  
good an idea as channelled ones.

What is a PITA has been taking that hump off the blank!


>
> Got the idea of using floor tiles from somebody else and promptly
> started thinking of how inexpensive that it could become.  The
> idea of using epoxy (what kind was my first question and the boat
> epoxy paint didn't come to mind) seemed to be a waste of
> expensive 5 minute epoxy so I just put the tiles in the plaster.
> The other thing was that I had a source of a fair bit of dental
> stone so that is what I used in the beginning.  25lb. of dental
> stone makes a fair number of tools to the point where the tiles
> were actually the more expensive part of the tool.  Lately, floor
> tiles have become hard to find locally so I've started using
> thick glass from anywhere.

I'm lucky in that my wife works in the flooring industry, so anytime a  
porcelain sample is discarded I get a new set of tiles gratis.

It's all good!

-73 de Mike N3LI -



From pdebaan at hotmail.com  Fri Apr 10 01:16:49 2009
From: pdebaan at hotmail.com (Peter De Baan)
Date: Thu, 9 Apr 2009 16:16:49 +0000
Subject: [ATM] please ID this tile tool material
In-Reply-To: <88E57575-631F-4519-A3F5-210C7BA4BABD@psu.edu>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<001901c9b88b$e2ccb040$8f78fea9@amd> 
	<88E57575-631F-4519-A3F5-210C7BA4BABD@psu.edu>
Message-ID: <BLU137-W109A53560FC0A1BAEFA8C8B2830@phx.gbl>




> Date: Thu, 9 Apr 2009 11:43:14 -0400
> From: mjc5 at psu.edu
> To: atm at atmlist.net
> Subject: Re: [ATM] please ID this tile tool material
> 
> 
> On Apr 8, 2009, at 4:51 PM, Bob May wrote:
> 
> > I'm afraid that I'm one of the persons putting forth the tile
> > tool idea.
> > I'm CHEAP!
> > The idea of usiong another piece of glass to grind a mirror is
> > just a big waste of material.  I'd rather use it to make another
> > mirror.
> 
> No argument there, Bob. When I used another blank to do my mirror, it  
> was already hogged with the glass blank. So I figured I might as well  
> use it. Along the way I learned a lot about why a solid tool isn't as  
> good an idea as channelled ones
> What is a PITA has been taking that hump off the blank!


Sorry for taking off the hump, if you leave the hump and instead 
grind the flat back you have half the work and have like a slumped 
mirror with added rigidety, you only need a ring support while working it
Peter 



> 

> 
> >
> > Got the idea of using floor tiles from somebody else and promptly
> > started thinking of how inexpensive that it could become.  The
> > idea of using epoxy (what kind was my first question and the boat
> > epoxy paint didn't come to mind) seemed to be a waste of
> > expensive 5 minute epoxy so I just put the tiles in the plaster.
> > The other thing was that I had a source of a fair bit of dental
> > stone so that is what I used in the beginning.  25lb. of dental
> > stone makes a fair number of tools to the point where the tiles
> > were actually the more expensive part of the tool.  Lately, floor
> > tiles have become hard to find locally so I've started using
> > thick glass from anywhere.
> 
> I'm lucky in that my wife works in the flooring industry, so anytime a  
> porcelain sample is discarded I get a new set of tiles gratis.
> 
> It's all good!
> 
> -73 de Mike N3LI -
> 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/

_________________________________________________________________
Rediscover Hotmail?: Get quick friend updates right in your inbox. 
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From mikell at optonline.net  Fri Apr 10 03:21:06 2009
From: mikell at optonline.net (Michael Lindner)
Date: Thu, 09 Apr 2009 14:21:06 -0400
Subject: [ATM] please ID this tile tool material
In-Reply-To: <002c01c9b7c7$a8767440$f9635cc0$@com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
Message-ID: <49DE3C92.3080706@optonline.net>

Berthold Hamburger wrote:
> However, I am under the impression that now most people just cast the tool
> around the tiles and I am wondering how that came to be? Clearly grinding
> the tiles down will also grind off plaster which in turn will scratch your
> glass. At least that is what I would imagine.

Welcome back to the hobby! I enjoyed (and freely borrowed from) your 
earlier projects, and look forward to doing so in the future.

I have *only* made tools by casting tiles embedded in dental plaster. 
Yes the plaster grinds away, and no I have never gotten scratches. It is 
my understanding that the plaster is softer than the glass (here comes a 
long thread :-) ). I do try to keep channels between the tiles, but 
there is still exposed plaster to be ground away. Not sure what would 
happen with  a tool that had sand in it, but since other members say the 
y use this, I'm sure they will chime in.

Clear skies,
-- 
Michael Lindner
http://www.starastronomy.org *** http://home.att.net/~mikel
http://www.atmsite.org *** http://www.atmlist.net

From jack.swaton at starryhost.com  Fri Apr 10 04:08:24 2009
From: jack.swaton at starryhost.com (Jack Swaton @ Starry Host)
Date: Thu, 9 Apr 2009 12:08:24 -0700
Subject: [ATM] Focal Point Spot
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd><398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd><002c01c9b7c7$a8767440$f9635cc0$@com>
	<49DE3C92.3080706@optonline.net> 
Message-ID: <56A6FDB0DBC14656B028D826926D9F53@MRBNOTEBOOK>

Where is the focal point of a path of light? For instance, if I were to
build a refractor (or newt for that matter) and I were to trace the rays
from the outside edge of the objective down to the converged focal point
(say 500mm), what does that converged point represent?  Is that they top of
the eyepiece? Is that some point inside the focuser? Is it some point inside
the eyepiece?

I'd like to build a folded refractor, but the question is relevant to a
number of projects.

Thanks,
Jack Swaton
www.StarryHost.com



From mikell at optonline.net  Fri Apr 10 04:34:46 2009
From: mikell at optonline.net (Michael Lindner)
Date: Thu, 09 Apr 2009 15:34:46 -0400
Subject: [ATM] Focal Point Spot
In-Reply-To: <56A6FDB0DBC14656B028D826926D9F53@MRBNOTEBOOK>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<49DE3C92.3080706@optonline.net>
	<56A6FDB0DBC14656B028D826926D9F53@MRBNOTEBOOK>
Message-ID: <49DE4DD6.9060603@optonline.net>

Jack Swaton @ Starry Host wrote:
> Where is the focal point of a path of light? For instance, if I were to
> build a refractor (or newt for that matter) and I were to trace the rays
> from the outside edge of the objective down to the converged focal point
> (say 500mm), what does that converged point represent?  Is that they top of
> the eyepiece? Is that some point inside the focuser? Is it some point inside
> the eyepiece?

That converged point is where an actual image is formed of what the 
telescope is pointed at. The position of the focal plane varies with the 
distance from the scope to the object (which is why we need a focuser).

If you mean "what part of the scope is that?" The answer is that the 
field stop of the eyepiece must be there for the image to be in focus. 
The field stop is the opening inside the barrel of the eyepiece, and is 
in different positions on different eyepieces (another reason to need a 
focuser).

For the purposes of designing a scope, I believe the rule of thumb is to 
plan for the focal point to be 1/4" above the top of the focuser 
drawtube when the focuser is racked all the way in.

Hope that helps. Clear skies
-- 
Michael Lindner
http://www.starastronomy.org *** http://home.att.net/~mikel
http://www.atmsite.org *** http://www.atmlist.net

From al at sgi.com  Fri Apr 10 04:44:38 2009
From: al at sgi.com (Alexis Cousein)
Date: Thu, 09 Apr 2009 21:44:38 +0200
Subject: [ATM] Focal Point Spot
In-Reply-To: <49DE4DD6.9060603@optonline.net>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>	<000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<49DE3C92.3080706@optonline.net>	<56A6FDB0DBC14656B028D826926D9F53@MRBNOTEBOOK>
	<49DE4DD6.9060603@optonline.net>
Message-ID: <49DE5026.5080201@sgi.com>

Michael Lindner wrote:
> 
> For the purposes of designing a scope, I believe the rule of thumb is to 
> plan for the focal point to be 1/4" above the top of the focuser 
> drawtube when the focuser is racked all the way in.
> 
That gets you into trouble with some combinations with barlows (notably
the TMB barlow), Speers-Waler eyepieces and a Paracorr (on Newts)
(as it expects the focal plane 18mm higher than its shoulder). 10mm
is already very aggressive, and 1/4" is really, really aggressive.

From al at sgi.com  Fri Apr 10 04:49:59 2009
From: al at sgi.com (Alexis Cousein)
Date: Thu, 09 Apr 2009 21:49:59 +0200
Subject: [ATM] Focal Point Spot
In-Reply-To: <49DE5026.5080201@sgi.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>	<000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<49DE3C92.3080706@optonline.net>	<56A6FDB0DBC14656B028D826926D9F53@MRBNOTEBOOK>	<49DE4DD6.9060603@optonline.net>
	<49DE5026.5080201@sgi.com>
Message-ID: <49DE5167.3060009@sgi.com>

Alexis Cousein wrote:
> That gets you into trouble with some combinations with barlows (notably
> the TMB barlow), Speers-Waler eyepieces and a Paracorr (on Newts)
> (as it expects the focal plane 18mm higher than its shoulder). 10mm
> is already very aggressive, and 1/4" is really, really aggressive.

Especially if it's a 2" focuser - the 2"-1.25" adpater from e.g. TeleVue
is 9mm high, so don't count on being able to focus most 1.25" eyepieces
except cheaper Pl?ssls and Televue 1.25" eyepieces (Tak LEs and Pentax XW
eyepieces will *not* focus).

From al at sgi.com  Fri Apr 10 05:37:44 2009
From: al at sgi.com (Alexis Cousein)
Date: Thu, 09 Apr 2009 22:37:44 +0200
Subject: [ATM] [offlist] Focal Point Spot
In-Reply-To: <a06230902c6040495b6c0@[72.234.152.196]>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>	<49DE3C92.3080706@optonline.net>
	<56A6FDB0DBC14656B028D826926D9F53@MRBNOTEBOOK>
	<49DE4DD6.9060603@optonline.net>	<49DE5026.5080201@sgi.com>
	<49DE5167.3060009@sgi.com> <a06230902c6040495b6c0@[72.234.152.196]>
Message-ID: <49DE5C98.60403@sgi.com>

Stan Truitt wrote:
> 
> [offlist]
> 
> 
> *Aloha Alexis,*
> 
> 
>> Alexis Cousein wrote:
>>> That gets you into trouble with some combinations with barlows (notably
>>> the TMB barlow), Speers-Waler eyepieces and a Paracorr (on Newts)
>>> (as it expects the focal plane 18mm higher than its shoulder). 10mm
>>> is already very aggressive, and 1/4" is really, really aggressive.
>>
>> Especially if it's a 2" focuser - the 2"-1.25" adpater from e.g. TeleVue
>> is 9mm high, so don't count on being able to focus most 1.25" eyepieces
>> except cheaper Pl?ssls and Televue 1.25" eyepieces (Tak LEs and Pentax XW
>> eyepieces will *not* focus).
> 
> 
> *Thanks for the very handy datapoints!*
> *
> *
> *I'm at the point of cutting my truss tubes to length.*
> *Having those uncertanties quantified is a splendid help.*
> *

If you're looking at using a Paracorr, 22-25mm outside of the racked in focuser
is usually what you want.

From rmay at nethere.com  Fri Apr 10 07:38:00 2009
From: rmay at nethere.com (Bob May)
Date: Thu, 9 Apr 2009 15:38:00 -0700
Subject: [ATM] My take on the whole tool thing. was Re: please ID
	thistile tool material
References: <Pine.LNX.4.44.0904091216340.11479-100000@uno.canit.se>
Message-ID: <001801c9b963$d769b620$8f78fea9@amd>

Guess part of the problem is language and regional.  We
provincials tend to call anything that is mixed with water and
isn't cement probably is plaster.  Being that there are hundreds
of different plaster type stones and so forth, assumptions are
often made.  Add in brand names and things get to be more fun!
The truth is that without a chemical anylsis of the stuff, you
really won't know exactly what it is.  What makes it more fun is
where did it come from?  Somebody could have bought something
from the states (you're often over here yourself) or it could be
something from the EU.
Have fun!
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Fri Apr 10 07:43:42 2009
From: rmay at nethere.com (Bob May)
Date: Thu, 9 Apr 2009 15:43:42 -0700
Subject: [ATM] My take on the whole tool thing. was Re: please
	IDthis	tile tool material
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd><49DD42BE.8020000@gmail.com><639227953.20090409105045@foucault.co.uk>
	<009e01c9b8fc$ba83a9b0$2f8afd10$@com>
Message-ID: <002501c9b964$a2c72c80$8f78fea9@amd>

One of the nice things about dental stone is that it is available
worldwide and is of a known good quality for the job.  Oftentimes
people can and have gotten what they need from their dentist for
free even!  Other stone materials may or may not be the right
kind of stuff and won't work as well.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Fri Apr 10 07:44:59 2009
From: rmay at nethere.com (Bob May)
Date: Thu, 9 Apr 2009 15:44:59 -0700
Subject: [ATM] My take on the whole tool thing. was Re: please ID
	thistile tool material
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd><398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd><002c01c9b7c7$a8767440$f9635cc0$@com><001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
	<639227953.20090409105045@foucault.co.uk>
Message-ID: <002801c9b964$d08c65e0$8f78fea9@amd>

As Mark said, Gotgrit is one place, then you might also want to
take a run through my website and read the article on mirror
grinding.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Fri Apr 10 07:52:46 2009
From: rmay at nethere.com (Bob May)
Date: Thu, 9 Apr 2009 15:52:46 -0700
Subject: [ATM] My take on the whole tool thing. was Re: please ID
	thistile tool material
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd><398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd><002c01c9b7c7$a8767440$f9635cc0$@com><001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
	<A70954BB-6D06-4C23-A661-4430F49164BD@psu.edu>
Message-ID: <004301c9b965$e94f65e0$8f78fea9@amd>

Wood has one big problem when being used for a tool.  It changes
size according to water and, even worse, the dimensional change
isn't even in all directions.  Add to that that you really don't
want to use two different materials with large differences in
expansion or you will end up with tools that bend a lot with temp
and/or water.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From holmmarkd at gmail.com  Fri Apr 10 08:12:37 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Thu, 09 Apr 2009 19:12:37 -0400
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <639227953.20090409105045@foucault.co.uk>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
	<639227953.20090409105045@foucault.co.uk>
Message-ID: <49DE80E5.2000403@gmail.com>

Richard in the UK wrote:
>  It would be very useful for those of us that
> live in the ROW if people could try to use generic names (like dental
> plaster) rather than trade names (like Hydrostone).
>
>   
The closest I can get to a generic name is to say that Hydrostone is a gypsum based cement, intended for casting statuary and architectural details.  In the US, some people decorate their yards or gardens with inexpensive statues.  Subjects include deer, oversized mushrooms, oversized frogs, cherubs, vases, bird baths, etc.  Roman Catholics sometimes have a small shrine with a statue of the Virgin Mary.  Also, buildings often have "fake", i.e. non-structural, details such as classical style columns, pediments, etc.  Since carved marble is expensive, cast Hydrostone, and related products are more often found in commercial buildings.  This is the sort of statuary Hydrostone is intended for, and if similar products are made in your locale, then a similar product is very likely in use.

Hydrostone is actually a mix of gypsum (plaster) and a small amount of portland cement, so it is really a hybrid product.  Both the plaster promoters and "cement" promoters can get behind it!



-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From russjocoy at hotmail.com  Fri Apr 10 09:10:37 2009
From: russjocoy at hotmail.com (Russell Jocoy)
Date: Thu, 9 Apr 2009 20:10:37 -0400
Subject: [ATM] Mirror Grinding tool material.
Message-ID: <COL116-W2EE52C6C5814F997224B0B8800@phx.gbl>


    I agree with Mark Holmes on his sumation of this link that has gone on forever.

These many ideas, and different material's have been gone over on this list many times.

Choose your medium, your material, and find out what work's best for you... None are wrong, but different. The Majority looks at not only the medium, but the time it takes to make the 'TOOL"....It all depend's on your time and money..this is another factor..

  Don't have alot of time.....Dental stone or Hydrocal with the tiles embeded...

      Got plenty of time, Make a work of art with Epoxy and sealing any thing that may possibly flack off of your creation....worry worry.   Many have been through this process,

and many will follow....You will never kill the surface, since you started at a grit close to sand on the beach...don't be afraid...this surface you are trying to create is more dense than your skull, or bone... Experiment, relax, grind, fine grind, polish, and worry about the scratch that looks like the grand canyon when you are polished out looking through a Foucault test..Damnit...I see nothing....Russ

_________________________________________________________________
Quick access to your favorite MSN content and Windows Live with Internet Explorer 8. 
http://ie8.msn.com/microsoft/internet-explorer-8/en-us/ie8.aspx?ocid=B037MSN55C0701A

From mokiman_210 at yahoo.com  Fri Apr 10 10:07:42 2009
From: mokiman_210 at yahoo.com (Curt Diggs)
Date: Thu, 9 Apr 2009 18:07:42 -0700 (PDT)
Subject: [ATM] My take on the whole tool thing. was Re: please ID this tile
	tool material
In-Reply-To: <mailman.67.1239316529.4635.atm@atmlist.net>
References: <mailman.67.1239316529.4635.atm@atmlist.net>
Message-ID: <958799.48290.qm@web50411.mail.re2.yahoo.com>

------------------------------

>Message: 2
>Date: Wed, 08 Apr 2009 20:35:10 -0400
>From: Mark Holm <holmmarkd at gmail.com>
>Subject: [ATM] My take on the whole tool thing. was Re: please ID this
>??? tile tool material
>To: atm at atmlist.net
>Message-ID: <49DD42BE.8020000 at gmail.com>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>I've been following these tool making discussions / arguments for 
>several years now on this list, and have come to a few conclusions:
>
>1.? There are several methods that work.

<snip>

I've made a bunch of tile tools for fine grinding for myself and a couple of other ATMers in the last several years, all using Hydrostone and tile mats. I'm finally near the end of the 90lb bag I bought three or four years ago (can't really remember). It's just dead easy to make a tool with this method and you can be grinding away within two hours or less after making the pour. 

With all respect to Dave Harbour and his well explained method of making a tile tool, simpler is better. I did it a couple of times David's way including the waxing and it works fine. After a couple of mirrors I decided to simplify the process. I cut the tile mat slightly smaller than the mirror and lay it on the mirror face up after covering the mirror with thin plastic wrap to protect it. If you dampen the mirror surface slightly the Saran wrap sticks like glue and its easy to get the bubbles out. I wrap a piece of thin aluminum flashing around the mirror with the flashing cut to the right width to get the thickness of tool I want with the ends secured with duct tape. Mix the Hydrostone to thickness of very thick cream (add 'stone to water, not the reverse) and then pour it directly into the mould. USe a small stick to work the bubbles out of the mix but a few don't hurt anything.

Wait about fifteen minutes and the stone will start to harden. Once the center is hard, I?remove the flashing and pull the tool off the mirror. While the 'stone is still a bit soft I take a wire brush and go?at the tile surface like a madman, brushing and removing some of the 'stone from between the tiles. Once I'm done I let it cure an hour or so then it's ready to use. The tiles usually seat fully to the mirror within a few wets. You can wax the tool per Dave's instructions?if you want to but I stopped doing?that?after I saw no difference in the grinding. The stone wears faster than the tiles and there's always a channel between the tiles. I've yet to have any problems with scratching from previous grits or from the Hydrostone. 

I use either a steel pipe coupling or a steel floor flange for rough grinding, depending on the size of the blank. They work very fast and once you learn to use them, you can get a reasonably spherical surface even when rough grinding.

Curt


      

From holmmarkd at gmail.com  Fri Apr 10 10:12:26 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Thu, 09 Apr 2009 21:12:26 -0400
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <49DE80E5.2000403@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
	<639227953.20090409105045@foucault.co.uk>
	<49DE80E5.2000403@gmail.com>
Message-ID: <49DE9CFA.8090301@gmail.com>

My command of languages other than English is too weak for me to web 
search for Hydrostone equivalents on the continent, but here are some UK 
leads:

http://www.theplasterwarehouse.co.uk/      These folks make stuff of 
plaster, similar to the sorts of things made from Hydrostone.  They have 
to have a raw material source.

http://www.ornateplaster.com/     Ditto.

http://www.architecturalmouldings.co.uk/     Ditto.

These folks supply:  
http://www.maragon.co.uk/arts-and-crafts.html#Init     From their web 
site, "For the US Gypsum products Hydrostone, Ultracal 30 and Hydrocal, 
the UK equivalents are Crystacast, Crystacal R and Herculite No.2 
respectively. "   They also have  "Cassini's outdoor casting Plaster.  
An extremely versatile water- and weather-resistant plaster for 
statuary, water-features, garden ornaments, etc".  Cassini's appears to 
set faster than Crystacast or Hydrostone, more like dental stone in that 
regard.


-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From thomas at moiler.com  Fri Apr 10 10:12:26 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Fri, 10 Apr 2009 11:12:26 +1000
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <49DE80E5.2000403@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>	<49DD42BE.8020000@gmail.com>	<639227953.20090409105045@foucault.co.uk>
	<49DE80E5.2000403@gmail.com>
Message-ID: <01c601c9b979$6a86cb90$3f9462b0$@com>

Well that answers the question that was simmering at the back of my mind!

I was wondering what would happen if I mixed some Portland cement into my
usual PoP (can't get the hydrostone type products here at all). 

So next tool I make will be a 50/50 mix of the two, and as I machine grind
now I don't have to worry about eh alkalinity of the result either!

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Mark Holm
Sent: Friday, 10 April 2009 9:13 AM
To: ATM List
Subject: Re: [ATM] My take on the whole tool thing. was Re: please ID this
tile tool material

The closest I can get to a generic name is to say that Hydrostone is a
gypsum based cement, intended for casting statuary and architectural
details.  In the US, some people decorate their yards or gardens with
inexpensive statues.  Subjects include deer, oversized mushrooms, oversized
frogs, cherubs, vases, bird baths, etc.  Roman Catholics sometimes have a
small shrine with a statue of the Virgin Mary.  Also, buildings often have
"fake", i.e. non-structural, details such as classical style columns,
pediments, etc.  Since carved marble is expensive, cast Hydrostone, and
related products are more often found in commercial buildings.  This is the
sort of statuary Hydrostone is intended for, and if similar products are
made in your locale, then a similar product is very likely in use.

Hydrostone is actually a mix of gypsum (plaster) and a small amount of
portland cement, so it is really a hybrid product.  Both the plaster
promoters and "cement" promoters can get behind it!




From holmmarkd at gmail.com  Fri Apr 10 10:20:27 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Thu, 09 Apr 2009 21:20:27 -0400
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <01c601c9b979$6a86cb90$3f9462b0$@com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>	<49DD42BE.8020000@gmail.com>	<639227953.20090409105045@foucault.co.uk>
	<49DE80E5.2000403@gmail.com> <01c601c9b979$6a86cb90$3f9462b0$@com>
Message-ID: <49DE9EDB.40204@gmail.com>

Thomas Janstrom wrote:
>  
> So next tool I make will be a 50/50 mix of the two, and as I machine grind
> now I don't have to worry about eh alkalinity of the result either!
>
>   
According to the USG material safety data sheet, the portland cement 
content of Hydrostone is not more than 5% by weight.  Don't know if 
simple mixing will work.  They might calcine it together.

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From mjc5 at psu.edu  Fri Apr 10 11:40:11 2009
From: mjc5 at psu.edu (Mike Coslo)
Date: Thu, 09 Apr 2009 21:40:11 -0500
Subject: [ATM] My take on the whole tool thing. was Re: please
 ID	thistile tool material
In-Reply-To: <004301c9b965$e94f65e0$8f78fea9@amd>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd><398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd><002c01c9b7c7$a8767440$f9635cc0$@com><001901c9b88b$e2ccb040$8f78fea9@amd>	<49DD42BE.8020000@gmail.com>	<A70954BB-6D06-4C23-A661-4430F49164BD@psu.edu>
	<004301c9b965$e94f65e0$8f78fea9@amd>
Message-ID: <49DEB18B.2010702@psu.edu>

Bob May wrote:
> Wood has one big problem when being used for a tool.  It changes
> size according to water and, even worse, the dimensional change
> isn't even in all directions.  Add to that that you really don't
> want to use two different materials with large differences in
> expansion or you will end up with tools that bend a lot with temp
> and/or water.

The really great thing is that while I used some really awful methods to 
hog and grind my mirror, like wood backing, plaster of Paris, and the 
same tool for both hogging out the mirror and rough through fine 
grinding, I'm happy to report that the resulting mirror did not suffer 
at all from my poor practices! 8^)

	- 73 de Mike N3LI -


From holmmarkd at gmail.com  Fri Apr 10 11:12:55 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Thu, 09 Apr 2009 22:12:55 -0400
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <49DE9CFA.8090301@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
	<639227953.20090409105045@foucault.co.uk>
	<49DE80E5.2000403@gmail.com> <49DE9CFA.8090301@gmail.com>
Message-ID: <49DEAB27.7030801@gmail.com>

Crystacast appears to be made by  BPB Formula  which has offices in the 
UK, France, Germany, Spain and Hungary.

Here is a product sheet    
http://www.bpbformula.com/PDF/EN/CRYSTACAST-ENGLISH.PDF

BPB Formula also makes Dental Stone   
http://www.bpbformula.com/en/content-3-21.aspx


Hate to say this, but, if I could find it from the suburbs of 
Pittsburgh, PA here in the good old US of A, you could have too.

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From hermit at outofoptions.org  Fri Apr 10 12:36:12 2009
From: hermit at outofoptions.org (hermit)
Date: Thu, 09 Apr 2009 23:36:12 -0400
Subject: [ATM] ATM materials and knowledge useful in other areas.
Message-ID: <49DEBEAC.1000103@outofoptions.org>

Years ago I salvaged a 12 inch woofer out of the trash cuz someone 
ditched both when only one was bad.  My son decided he wanted it.  When 
looking for a design, he found several that use a sono-tube.  Cut some 
circles from MDF from an old project and all he had to buy was a sub 
woofer amp and some batting to line the tube.

Now this just came to the atm-owner list:

i'm going to use the instructions on this page to make my own drums out 
of fiberglass
http://www.atmsite.org/contrib/Kohut/fgtube/

drums as in rock out on a drum set drums. why, because fiberglass drums 
are expensive to buy and rare

I wasn't going to mention the sub-woofer enclosures, but this email came 
in and I though, why not?  It might be fun to know if anyone else has 
been able to use crossover knowledge in other projects as long as it 
doesn't get out of hand.   I would not have thought of either of these 
myself.  Probably just not an area of interest for me.

Ken Lowther

From thomas at moiler.com  Fri Apr 10 13:59:42 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Fri, 10 Apr 2009 14:59:42 +1000
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <49DE9EDB.40204@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>	<49DD42BE.8020000@gmail.com>	<639227953.20090409105045@foucault.co.uk>
	<49DE80E5.2000403@gmail.com> <01c601c9b979$6a86cb90$3f9462b0$@com>
	<49DE9EDB.40204@gmail.com>
Message-ID: <028901c9b999$2a0d2850$7e2778f0$@com>

Hmmm, does make the result easier on the skin too. I wonder just how they
mix it. 

I guess I'll have to do some experiments to see what I get at various ratios
in so far as water resistance. I'm quite happy with the stability of PoP is
it's given a coat or two of paint prior to use and a couple of follow up
coats as you progress through the grits (don't need to do it every grit
change, it's more to seal the surface than prevent contamination).

Well that little side project will have to keep for a bit, I have a 16"
mirror to finish before I head off to the US on holidays next month....

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 


-----Original Message-----
From: Mark Holm [mailto:holmmarkd at gmail.com] 
Sent: Friday, 10 April 2009 11:20 AM
To: thomas at moiler.com
Cc: atm at atmlist.net
Subject: Re: [ATM] My take on the whole tool thing. was Re: please ID this
tile tool material

Thomas Janstrom wrote:
>  
> So next tool I make will be a 50/50 mix of the two, and as I machine grind
> now I don't have to worry about eh alkalinity of the result either!
>
>   
According to the USG material safety data sheet, the portland cement 
content of Hydrostone is not more than 5% by weight.  Don't know if 
simple mixing will work.  They might calcine it together.

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com



From b-hamburger at ya.com  Fri Apr 10 17:11:53 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Fri, 10 Apr 2009 10:11:53 +0200
Subject: [ATM] please ID this tile tool material
In-Reply-To: <49DE3C92.3080706@optonline.net>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se>
	<002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net>
	<000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<49DE3C92.3080706@optonline.net>
Message-ID: <000c01c9b9b4$031c7be0$095573a0$@com>

Hi Michael,

Right now it is more likely, I will borrow from you guys ;-). However, I am
glad to hear that some of my (small) accomplishments have been used
elsewhere too! 
I am looking forward to participating again more actively in the ATM world
and right now I am enjoying reading the list especially as it is just as
friendly, clean and informative as it was 10 years ago!

Best wishes

Berthold

-- 
Berthold Hamburger - Cellist/Spain
Email: behambu at artinso.com
http://www.artinso.com
http://www.astro.artinso.com

> -----Original Message-----
> From: Michael Lindner [mailto:mikell at optonline.net]
> Sent: jueves, 09 de abril de 2009 20:21
> To: Berthold Hamburger
> Cc: atm at atmlist.net
> Subject: Re: [ATM] please ID this tile tool material
> 
> Berthold Hamburger wrote:
> > However, I am under the impression that now most people just cast the
> tool
> > around the tiles and I am wondering how that came to be? Clearly
> grinding
> > the tiles down will also grind off plaster which in turn will scratch
> your
> > glass. At least that is what I would imagine.
> 
> Welcome back to the hobby! I enjoyed (and freely borrowed from) your
> earlier projects, and look forward to doing so in the future.
> 
> I have *only* made tools by casting tiles embedded in dental plaster.
> Yes the plaster grinds away, and no I have never gotten scratches. It is
> my understanding that the plaster is softer than the glass (here comes a
> long thread :-) ). I do try to keep channels between the tiles, but
> there is still exposed plaster to be ground away. Not sure what would
> happen with  a tool that had sand in it, but since other members say the
> y use this, I'm sure they will chime in.
> 
> Clear skies,
> --
> Michael Lindner
> http://www.starastronomy.org *** http://home.att.net/~mikel
> http://www.atmsite.org *** http://www.atmlist.net


From richard at foucault.co.uk  Fri Apr 10 19:43:44 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Fri, 10 Apr 2009 11:43:44 +0100
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <49DEAB27.7030801@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>
	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>
	<002c01c9b7c7$a8767440$f9635cc0$@com>
	<001901c9b88b$e2ccb040$8f78fea9@amd> <49DD42BE.8020000@gmail.com>
	<639227953.20090409105045@foucault.co.uk>
	<49DE80E5.2000403@gmail.com> <49DE9CFA.8090301@gmail.com>
	<49DEAB27.7030801@gmail.com>
Message-ID: <1371395541.20090410114344@foucault.co.uk>

Hello Mark,

Friday, April 10, 2009, 3:12:55 AM, you wrote:

> Crystacast appears to be made by  BPB Formula  which has offices in the
> UK, France, Germany, Spain and Hungary.

> Here is a product sheet    
> http://www.bpbformula.com/PDF/EN/CRYSTACAST-ENGLISH.PDF

> BPB Formula also makes Dental Stone   
> http://www.bpbformula.com/en/content-3-21.aspx


> Hate to say this, but, if I could find it from the suburbs of 
> Pittsburgh, PA here in the good old US of A, you could have too.


Who was saying they couldn't find dental stone in Europe then Mark?

-- 
Best regards,
 Richard in the UK


From stainless_steel at suddenlink.net  Fri Apr 10 23:59:51 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Fri, 10 Apr 2009 09:59:51 -0500
Subject: [ATM] ATM: Re: Focal point spot-
Message-ID: <DFF5D37F41BB4E4D8C334B1641880F78@R101>

Jack,

Many amateurs do not have a clear concept that the focal plane is not a 
point; this is the case only for a single star in the field of view. The 
focal PLANE us what you want to find; to this, you would add the focal 
length of your longest eyepiece (longest focal length eyepiece)- a very 
lucid discussion of the concept off the way an image is built up in the 
focal plane can be found in my treatise, here:

http://www.atmsite.org/contrib/Harbour/Foucault.html

I have included this discussion of the focal plane, and the mechanics of how 
an image is formed across the entire focal plane because beginners often 
have the erroneous notion, due to incomple illustrations in books, that 
there is only a focal POINT. This is, of course, an entirely erroneous 
concept.

LZ-130
(Davey)

>Where is the focal point of a path of light? For instance, if I were to
>build a refractor (or newt for that matter) and I were to trace the rays
>from the outside edge of the objective down to the converged focal point
>(say 500mm), what does that converged point represent?  Is that they top of
>the eyepiece? Is that some point inside the focuser? Is it some point 
>inside
>the eyepiece?

>I'd like to build a folded refractor, but the question is relevant to a
>number of projects.

>Thanks,
>Jack Swaton
www.StarryHost.com



From al at sgi.com  Sat Apr 11 00:08:42 2009
From: al at sgi.com (Alexis Cousein)
Date: Fri, 10 Apr 2009 17:08:42 +0200
Subject: [ATM] ATM: Re: Focal point spot-
In-Reply-To: <DFF5D37F41BB4E4D8C334B1641880F78@R101>
References: <DFF5D37F41BB4E4D8C334B1641880F78@R101>
Message-ID: <49DF60FA.6080508@sgi.com>

stainless_steel at suddenlink.net wrote:
> because beginners 
> often have the erroneous notion, due to incomple illustrations in books, 
> that there is only a focal POINT. This is, of course, an entirely 
> erroneous concept.
> 

It's not erroneous, just incomplete (if you think that's all that matters).

The focal point is the point on the focal plane for the on-axis object
(if the axis is ambiguous as it is in certain miscollimated scopes,
for the axis that delivers minimal aberrations or eliminates the
most troublesome aberration, like coma in an SCT), and so it really
*does* exist.

From b-hamburger at ya.com  Sat Apr 11 00:11:16 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Fri, 10 Apr 2009 17:11:16 +0200
Subject: [ATM] ATM: Re: Focal point spot-
In-Reply-To: <DFF5D37F41BB4E4D8C334B1641880F78@R101>
References: <DFF5D37F41BB4E4D8C334B1641880F78@R101>
Message-ID: <003301c9b9ee$9946f890$cbd4e9b0$@com>

I think he asks where the focal plane is formed "geographically" along the
light path.
To my understanding the rays converge in a focal plane at the field stop of
the eyepiece and leave the eyepiece in a parallel manner to form what we
call the airy disc which is projected on the retina.

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 stainless_steel at suddenlink.net
> Sent: viernes, 10 de abril de 2009 17:00
> To: ATM list
> Subject: [ATM] ATM: Re: Focal point spot-
> 
> Jack,
> 
> Many amateurs do not have a clear concept that the focal plane is not a
> point; this is the case only for a single star in the field of view. The
> focal PLANE us what you want to find; to this, you would add the focal
> length of your longest eyepiece (longest focal length eyepiece)- a very
> lucid discussion of the concept off the way an image is built up in the
> focal plane can be found in my treatise, here:
> 
> http://www.atmsite.org/contrib/Harbour/Foucault.html
> 
> I have included this discussion of the focal plane, and the mechanics of
> how
> an image is formed across the entire focal plane because beginners often
> have the erroneous notion, due to incomple illustrations in books, that
> there is only a focal POINT. This is, of course, an entirely erroneous
> concept.
> 
> LZ-130
> (Davey)
> 
> >Where is the focal point of a path of light? For instance, if I were to
> >build a refractor (or newt for that matter) and I were to trace the
> rays
> >from the outside edge of the objective down to the converged focal
> point
> >(say 500mm), what does that converged point represent?  Is that they
> top of
> >the eyepiece? Is that some point inside the focuser? Is it some point
> >inside
> >the eyepiece?
> 
> >I'd like to build a folded refractor, but the question is relevant to a
> >number of projects.
> 
> >Thanks,
> >Jack Swaton
> www.StarryHost.com
> 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From stainless_steel at suddenlink.net  Sat Apr 11 00:19:09 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Fri, 10 Apr 2009 10:19:09 -0500
Subject: [ATM] ATM: Re: Berthold's note about the list-
Message-ID: <5A5FCF34B8BD4CEEA9979E10DFCB8109@R101>


I thought I would comment on one of Berthold's comments about the list-

It is everything he says it is. But what is most significant to me is that 
he said it is "friendly". Friendly it is, indeed- we are an elite society, 
standing above, I believe, the other ATM forums, which define themselves 
somewhat narrowly, usually. Our combined experience is enormous, and that we 
share it freely is very significant.

It is true that I put together a book detailing my best articles, for the 
most part, and it is for sale; however, all of these articles are availble 
freely to anyone who asks for them in digital form as attachments, and 
"Understanding Foucault" is available to read as webpages at the atm site, 
and on Bob May's site, and at "The ATM's workshop", here:

http://www.atm-workshop.com/foucault.html

It is in this spirit of friendhsip that, like everyone else, I offer all I 
have learned (especially through experience) freely to all of my friends and 
colleagues. Let's make mirrors, and telescopes!!!

I am proud that all of you have accepted me as a colleague; thank you all.

LZ-130

>Hi Michael,

>Right now it is more likely, I will borrow from you guys ;-). However, I am
>glad to hear that some of my (small) accomplishments have been used
>elsewhere too!
>I am looking forward to participating again more actively in the ATM world
>and right now I am enjoying reading the list especially as it is just as
>friendly, clean and informative as it was 10 years ago!

>Best wishes

>Berthold


From stainless_steel at suddenlink.net  Sat Apr 11 03:35:44 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Fri, 10 Apr 2009 13:35:44 -0500
Subject: [ATM] ATM: Re: Berthold"s Answer about focal plane location-
Message-ID: <B5688C0B96FE48BC92E17283B5D0C4C5@R101>


Berthold:

Your answer is the most concise and all-encompassing that I have seen yet. I 
failed to provide nearly as good an answer.

The rays of light are said to be "afocal" when the eyepiece is focused for 
the infinity position of the healthy (perfectly healthy, i.e., no myopia or 
dystopia) human eye. Each bundle of rays, although heading in a different 
direction to form the image, are parallel in this case.

Not for me: I am nearsighted; this is the beauty of the focuser- it can take 
into acount both nearsighted and far sighted vision for different people, 
and they do not have to wear their glasses. Unfortunately, it cannot take 
into consideration (i.e., cannot correct for) someone's eye that has 
astigmatism.

You are far more precise than me in your statement that the focal plane 
should lie in the focal plane (usually where the field stop is) of the 
eyepiece. Preferably, one should take this into account when building one's 
scope- provide for the longest focal length eyepiece, keeping in mind to 
locate it in the field stop of the eyepiece.

I had an eyepiece once that showed any particle of something in the focal 
plane, which was located inside of the field lens. Awful. If someone knows 
the name of this kind of eyepiece, please chime in. I have forgotten.

Well stated, with an economy of words. You are an adept teacher, Berthold.

DLZ-130

>I think he asks where the focal plane is formed "geographically" along the
>light path.
>To my understanding the rays converge in a focal plane at the field stop of
>the eyepiece and leave the eyepiece in a parallel manner to form what we
>call the airy disc which is projected on the retina.

>Berthold



From holmmarkd at gmail.com  Sat Apr 11 07:06:01 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Fri, 10 Apr 2009 18:06:01 -0400
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
 tile tool material
In-Reply-To: <49DEAB27.7030801@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>
	<49DD42BE.8020000@gmail.com>
	<639227953.20090409105045@foucault.co.uk>
	<49DE80E5.2000403@gmail.com> <49DE9CFA.8090301@gmail.com>
	<49DEAB27.7030801@gmail.com>
Message-ID: <49DFC2C9.8090808@gmail.com>

Hydrostone is available in Australia, at least in NSW and Victoria from

http://www.barnesonline.com.au/productsByCategory.asp?intCatalogID=15&strCatalog_NAME=Gypsums%2C+Plasters+%26+Allied+Products


-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From thomas at moiler.com  Sat Apr 11 07:58:40 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Sat, 11 Apr 2009 08:58:40 +1000
Subject: [ATM] My take on the whole tool thing. was Re: please ID this
	tile tool material
In-Reply-To: <49DFC2C9.8090808@gmail.com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>	<49DD42BE.8020000@gmail.com>	<639227953.20090409105045@foucault.co.uk>	<49DE80E5.2000403@gmail.com>
	<49DE9CFA.8090301@gmail.com>	<49DEAB27.7030801@gmail.com>
	<49DFC2C9.8090808@gmail.com>
Message-ID: <018c01c9ba2f$e511ad60$af350820$@com>

I just found a "local" supply of dental plaster, if a 60mile round trip
counts as local, seeing as the stuff is listed as alkaline (for the purposes
of Australia Post), and comes in 20kg bags which make posting them a no-no
(I'm sure with the right weasel words you could do it, but why risk it when
the bag is less than AU$20 and postage is going to run AU$50 plus?), so come
Tuesday I'm doing a little road trip!

Apparently (so I hear) this place just opened last month, so talk about good
timing.....

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Mark Holm
Sent: Saturday, 11 April 2009 8:06 AM
To: ATM List
Subject: Re: [ATM] My take on the whole tool thing. was Re: please ID this
tile tool material

Hydrostone is available in Australia, at least in NSW and Victoria from

http://www.barnesonline.com.au/productsByCategory.asp?intCatalogID=15&strCat
alog_NAME=Gypsums%2C+Plasters+%26+Allied+Products


-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com

_______________________________________________
ATM mailing list http://www.atmlist.net/


From holmmarkd at gmail.com  Sat Apr 11 11:07:56 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Fri, 10 Apr 2009 22:07:56 -0400
Subject: [ATM] Sources of Hydrostone in Europe and Australia
Message-ID: <49DFFB7C.6020307@gmail.com>

I am summarizing this under a more meaningful subject, so that it will 
be easier to find in the archive if anybody is looking in the future.


Hydrostone is a high strength plaster (technically a gypsum cement) 
manufactured by US Gypsum (aka USG).   
http://gypsumsolutions.com/search_details_lit.asp?DocId=518
Hydrostone is recommended as a near equivalent to dental stone for the 
production of mirror grinding tools using the tile-in-stone method.  
(Some think Hydrostone is actually superior for larger tools because it 
has a somewhat longer working time than most dental stone products.)  
Hydrostone is widely available in the US, and probably in Canada.


One product, reputed to be equivalent to Hydrostone, which is available 
in Europe is Crystacast made by BPB Formula.  BPB Formula has offices in 
the UK, France, Germany, Spain and Hungary.

A product sheet for Crystacast is at 
http://www.bpbformula.com/PDF/EN/CRYSTACAST-ENGLISH.PDF

One dealer for Crystacast in the UK is 
http://www.maragon.co.uk/arts-and-crafts.html#Init
Sepal-Maragon, 1 Woodhall Farm, Hatfield, Herts, AL9 5NU.  Tel 01707 276156

One dealer for Crystacast in The Netherlands is FormX   
http://www.formx.nl/Shop/assets/s2dmain.html?http://www.formx.nl/Shop/10000094b0133510b/100000957a13a0787/10000098440bce736.html

FormX / aff-materialen
tel: 020-4182105
fax: 020-4180385
email: info at formx.nl

bezoekadres:  FormX - KNSM-Laan 810 - 1019 LT Amsterdam
Postadres:  Levantkade 271, 1019 MH Amsterdam


BPB Formula also make dental stone  
http://www.bpbformula.com/en/content-3-21.aspx


In Australia, one dealer for Hydrostone is Barnes Online 
http://www.barnesonline.com.au/productsByCategory.asp?intCatalogID=15&strCatalog_NAME=Gypsums%2C+Plasters+%26+Allied+Products 
<http://www.barnesonline.com.au/productsByCategory.asp?intCatalogID=15&strCatalog_NAME=Gypsums%2C+Plasters+%26+Allied+Products>

53 King Street
Newtown NSW 2042

Store Phone No: (02) 9557 9056
All technical enquiries call Head Office on 1300 731 497


40 - 42 Swan Street
Richmond VIC 3121

Ph:  (03) 9428 5511
Fax: (03) 9428 5533


-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From russjocoy at hotmail.com  Sat Apr 11 11:26:11 2009
From: russjocoy at hotmail.com (Russell Jocoy)
Date: Fri, 10 Apr 2009 22:26:11 -0400
Subject: [ATM] The reason for this list..
Message-ID: <COL116-W118A546EFBE870E45732C7B8810@phx.gbl>


 

 

   Hello all, Davey made a profound statement about the meaning of this list........It is to help, promote, and influence new reader's or contact's into the realm of ATM...Amature Telescope Makers... This is our passion, and we hope that other's will join our passion.

  We must always remember the time when we needed help in our adventure into the hand's on construction of a telescope.. The basic's, you know, primary, secondary, and then the deep stuff, spiders, primary support...secondary alignment.. Let alone creating your own primary mirror...  This list has helped thousand's (my estimate) make a telescope to look at the stars.... I feel this is a great goal that has been achieved... What we as ATM's  must realize is our group is growing, with experienced ATM's and new ATM's and we need to give help,  and we alway's have.. but sometimes we go off course and ..Quibble, this confuses me and everyone else. The basic's are written in stone, the following questions that everyone ask's are up to this list, because we are the cutting edge of this ART..

   If you do not consider this an art,, you are not involved.. Any who have figured a telescope mirror know it is an ART...at least on this list it is...  Russ Jocoy

_________________________________________________________________
Rediscover Hotmail?: Get quick friend updates right in your inbox. 
http://windowslive.com/RediscoverHotmail?ocid=TXT_TAGLM_WL_HM_Rediscover_Updates1_042009

From anishmangal2002 at gmail.com  Sat Apr 11 13:54:20 2009
From: anishmangal2002 at gmail.com (Anish Mangal)
Date: Sat, 11 Apr 2009 10:24:20 +0530
Subject: [ATM] The reason for this list..
In-Reply-To: <COL116-W118A546EFBE870E45732C7B8810@phx.gbl>
References: <COL116-W118A546EFBE870E45732C7B8810@phx.gbl>
Message-ID: <47eee29a0904102154w3d0e3a5dq379d96a996adb825@mail.gmail.com>

I totally agree with you Russ. The list was invaluable for a rookie ATM like
me to build myself an 8 inch dob from scratch. Completion of the telescope
(and the things it has already showed me!) was pretty much like a dream come
true. ATM is very much an evolving art with  enormous scope for new
inovations.

I already have plans of motorizing my dob mount, and will put them up for
discussion once I formalize them.

Thanks to everyone on the list,
Anish Mangal
New Delhi


On 4/11/09, Russell Jocoy <russjocoy at hotmail.com> wrote:
>
>
>
>
>
>
>    Hello all, Davey made a profound statement about the meaning of this
> list........It is to help, promote, and influence new reader's or contact's
> into the realm of ATM...Amature Telescope Makers... This is our passion, and
> we hope that other's will join our passion.
>
>   We must always remember the time when we needed help in our adventure
> into the hand's on construction of a telescope.. The basic's, you know,
> primary, secondary, and then the deep stuff, spiders, primary
> support...secondary alignment.. Let alone creating your own primary
> mirror...  This list has helped thousand's (my estimate) make a telescope to
> look at the stars.... I feel this is a great goal that has been achieved...
> What we as ATM's  must realize is our group is growing, with experienced
> ATM's and new ATM's and we need to give help,  and we alway's have.. but
> sometimes we go off course and ..Quibble, this confuses me and everyone
> else. The basic's are written in stone, the following questions that
> everyone ask's are up to this list, because we are the cutting edge of this
> ART..
>
>    If you do not consider this an art,, you are not involved.. Any who have
> figured a telescope mirror know it is an ART...at least on this list it
> is...  Russ Jocoy
>
>
> _________________________________________________________________
> Rediscover Hotmail?: Get quick friend updates right in your inbox.
>
> http://windowslive.com/RediscoverHotmail?ocid=TXT_TAGLM_WL_HM_Rediscover_Updates1_042009
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>

From b-hamburger at ya.com  Sat Apr 11 16:54:30 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Sat, 11 Apr 2009 09:54:30 +0200
Subject: [ATM] My take on the whole tool thing. was Re: please ID
	this	tile tool material
In-Reply-To: <018c01c9ba2f$e511ad60$af350820$@com>
References: <Pine.LNX.4.44.0904061821240.23155-100000@uno.canit.se><002501c9b6f3$d5ca8fa0$8f78fea9@amd>	<398213C674F7554AB0F55401DF29FBD101F8BB0C@ziggy.decatur-al.net><000b01c9b7c6$81cbe240$8f78fea9@amd>	<002c01c9b7c7$a8767440$f9635cc0$@com>	<001901c9b88b$e2ccb040$8f78fea9@amd>	<49DD42BE.8020000@gmail.com>	<639227953.20090409105045@foucault.co.uk>	<49DE80E5.2000403@gmail.com>	<49DE9CFA.8090301@gmail.com>	<49DEAB27.7030801@gmail.com>	<49DFC2C9.8090808@gmail.com>
	<018c01c9ba2f$e511ad60$af350820$@com>
Message-ID: <00ab01c9ba7a$bffd3a30$3ff7ae90$@com>

Hi,

Actually dentists and dental labs don't usually leave office to get
supplies. They get them delivered at a nominal rate by dental/medical supply
warehouses. You find them probably almost anywhere in the world and more and
more on the internet also. I tend to have tremendous difficulties to find
materials where I live. Anything from T-nuts to motors, pulleys, plastics
etc. is tremendously complicated. However, dental plaster really never is a
problem due to these outlets. They may ask you for the name of your clinic,
or maybe your tax ID. In the worst case ask your dentist to order an extra
4-20kg tub. You get anything from dental plaster to Hydrocal.

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 Thomas Janstrom
> Sent: s?bado, 11 de abril de 2009 0:59
> To: 'Mark Holm'; 'ATM List'
> Subject: Re: [ATM] My take on the whole tool thing. was Re: please ID
> this tile tool material
> 
> I just found a "local" supply of dental plaster, if a 60mile round trip
> counts as local, seeing as the stuff is listed as alkaline (for the
> purposes
> of Australia Post), and comes in 20kg bags which make posting them a no-
> no
> (I'm sure with the right weasel words you could do it, but why risk it
> when
> the bag is less than AU$20 and postage is going to run AU$50 plus?), so
> come
> Tuesday I'm doing a little road trip!
> 
> Apparently (so I hear) this place just opened last month, so talk about
> good
> timing.....
> 
> Cheers, Thomas Janstrom.
> Little Gems.
> http://tjlittlegems.com
> 
> -----Original Message-----
> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf
> Of
> Mark Holm
> Sent: Saturday, 11 April 2009 8:06 AM
> To: ATM List
> Subject: Re: [ATM] My take on the whole tool thing. was Re: please ID
> this
> tile tool material
> 
> Hydrostone is available in Australia, at least in NSW and Victoria from
> 
> http://www.barnesonline.com.au/productsByCategory.asp?intCatalogID=15&st
> rCat
> alog_NAME=Gypsums%2C+Plasters+%26+Allied+Products
> 
> 
> --
> Mark Holm
> markholm at verizon.net
> holmmarkd at gmail.com
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From dlwebb at canit.se  Sat Apr 11 19:49:13 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Sat, 11 Apr 2009 12:49:13 +0200 (MET DST)
Subject: [ATM] Sources of Hydrostone in Europe and Australia
In-Reply-To: <49DFFB7C.6020307@gmail.com>
Message-ID: <Pine.LNX.4.44.0904111247200.765-100000@uno.canit.se>

On Fri, 10 Apr 2009, Mark Holm wrote:

> Hydrostone is widely available in the US, and probably in Canada.

I believe "The Hydrostone" is in Canada. I wonder if there is
a connection.

I have contacted USG in Sweden to see if it is sold here.

Dominc


From b-hamburger at ya.com  Sat Apr 11 20:18:00 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Sat, 11 Apr 2009 13:18:00 +0200
Subject: [ATM] The reason for this list..
In-Reply-To: <47eee29a0904102154w3d0e3a5dq379d96a996adb825@mail.gmail.com>
References: <COL116-W118A546EFBE870E45732C7B8810@phx.gbl>
	<47eee29a0904102154w3d0e3a5dq379d96a996adb825@mail.gmail.com>
Message-ID: <00c001c9ba97$2d9d4780$88d7d680$@com>

Hi Anish,

You might come to our scope drive list that deals with all the aspects of motorizing. It was created years ago, in order to separate the building and motorizing topics. It helps to keep both lists more manageable.
I sent you an invitation to join.

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 Anish Mangal
> Sent: s?bado, 11 de abril de 2009 6:54
> To: Russell Jocoy
> Cc: ATM list
> Subject: Re: [ATM] The reason for this list..
> 
> I totally agree with you Russ. The list was invaluable for a rookie ATM
> like
> me to build myself an 8 inch dob from scratch. Completion of the
> telescope
> (and the things it has already showed me!) was pretty much like a dream
> come
> true. ATM is very much an evolving art with  enormous scope for new
> inovations.
> 
> I already have plans of motorizing my dob mount, and will put them up
> for
> discussion once I formalize them.
> 
> Thanks to everyone on the list,
> Anish Mangal
> New Delhi
> 
> 
> On 4/11/09, Russell Jocoy <russjocoy at hotmail.com> wrote:
> >
> >
> >
> >
> >
> >
> >    Hello all, Davey made a profound statement about the meaning of
> this
> > list........It is to help, promote, and influence new reader's or
> contact's
> > into the realm of ATM...Amature Telescope Makers... This is our
> passion, and
> > we hope that other's will join our passion.
> >
> >   We must always remember the time when we needed help in our
> adventure
> > into the hand's on construction of a telescope.. The basic's, you
> know,
> > primary, secondary, and then the deep stuff, spiders, primary
> > support...secondary alignment.. Let alone creating your own primary
> > mirror...  This list has helped thousand's (my estimate) make a
> telescope to
> > look at the stars.... I feel this is a great goal that has been
> achieved...
> > What we as ATM's  must realize is our group is growing, with
> experienced
> > ATM's and new ATM's and we need to give help,  and we alway's have..
> but
> > sometimes we go off course and ..Quibble, this confuses me and
> everyone
> > else. The basic's are written in stone, the following questions that
> > everyone ask's are up to this list, because we are the cutting edge of
> this
> > ART..
> >
> >    If you do not consider this an art,, you are not involved.. Any who
> have
> > figured a telescope mirror know it is an ART...at least on this list
> it
> > is...  Russ Jocoy
> >
> >
> > _________________________________________________________________
> > Rediscover Hotmail?: Get quick friend updates right in your inbox.
> >
> >
> http://windowslive.com/RediscoverHotmail?ocid=TXT_TAGLM_WL_HM_Rediscover
> _Updates1_042009
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From thomas at moiler.com  Sat Apr 11 20:36:55 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Sat, 11 Apr 2009 21:36:55 +1000
Subject: [ATM] Sources of Hydrostone in Europe and Australia
In-Reply-To: <Pine.LNX.4.44.0904111247200.765-100000@uno.canit.se>
References: <49DFFB7C.6020307@gmail.com>
	<Pine.LNX.4.44.0904111247200.765-100000@uno.canit.se>
Message-ID: <034901c9ba99$d28b0aa0$77a11fe0$@com>

For the Australians who haven't cottoned on to this yet, this is the product
to ask for: GyprockT Dental Plaster, from your local CSR Gyprock stockist.

Had a real "Well DUH" moment yesterday when I worked this one out, finally!

There is also a "statuary" casting plaster, but the data I found isn't clear
if it's actually water proof, and I'll be asking about it when I go shopping
for dental plaster Tuesday (Monday being a holiday over here).

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 


-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Dominic-Luc Webb
Sent: Saturday, 11 April 2009 8:49 PM
To: ATM Superheros
Subject: Re: [ATM] Sources of Hydrostone in Europe and Australia

On Fri, 10 Apr 2009, Mark Holm wrote:

> Hydrostone is widely available in the US, and probably in Canada.

I believe "The Hydrostone" is in Canada. I wonder if there is
a connection.

I have contacted USG in Sweden to see if it is sold here.

Dominc

_______________________________________________
ATM mailing list http://www.atmlist.net/


From richard at foucault.co.uk  Sat Apr 11 21:01:26 2009
From: richard at foucault.co.uk (Richard in the UK)
Date: Sat, 11 Apr 2009 13:01:26 +0100
Subject: [ATM] Sources of Hydrostone in Europe and Australia
In-Reply-To: <Pine.LNX.4.44.0904111247200.765-100000@uno.canit.se>
References: <49DFFB7C.6020307@gmail.com>
	<Pine.LNX.4.44.0904111247200.765-100000@uno.canit.se>
Message-ID: <142415079.20090411130126@foucault.co.uk>

Hello Dominic-Luc,

Saturday, April 11, 2009, 11:49:13 AM, you wrote:

> I have contacted USG in Sweden to see if it is sold here.

I did this a while back Dominic and the manufacturers say it is only
distributed in continental North America. Not that it really matters,
it is just one brand and type of dental plaster which is available in
many grades world wide. There is nothing magical about Hydrostone,
just that our US friends use the word Hydrostone to mean dental
plaster in the same way people in the UK (at least) use the word
Hoover to mean vacuum cleaner.

-- 
Best regards,
 Richard in the UK


From b-hamburger at ya.com  Sat Apr 11 21:22:36 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Sat, 11 Apr 2009 14:22:36 +0200
Subject: [ATM] The reason for this list..
In-Reply-To: <Pine.LNX.4.44.0904111328210.5821-100000@uno.canit.se>
References: <00c001c9ba97$2d9d4780$88d7d680$@com>
	<Pine.LNX.4.44.0904111328210.5821-100000@uno.canit.se>
Message-ID: <00c401c9baa0$3416c150$9c4443f0$@com>

Done. Anybody else who wants to join can just go to
http://tech.groups.yahoo.com/group/scope-drive

Berthold

-- 
Berthold Hamburger - Cellist/Spain
Email: behambu at artinso.com
http://www.artinso.com
http://www.astro.artinso.com


> -----Original Message-----
> From: Dominic-Luc Webb [mailto:dlwebb at canit.se]
> Sent: s?bado, 11 de abril de 2009 13:29
> To: Berthold Hamburger
> Subject: Re: [ATM] The reason for this list..
> 
> On Sat, 11 Apr 2009, Berthold Hamburger wrote:
> 
> > Hi Anish,
> >
> > You might come to our scope drive list that deals with all the aspects
> of motorizing. It was created years ago, in order to separate the
> building and motorizing topics. It helps to keep both lists more
> manageable.
> > I sent you an invitation to join.
> >
> > Berthold
> 
> Could you please send me info as well?
> 
> Thanks in advance,
> 
> Dominic


From jack.swaton at starryhost.com  Sat Apr 11 22:22:56 2009
From: jack.swaton at starryhost.com (Jack Swaton @ Starry Host)
Date: Sat, 11 Apr 2009 06:22:56 -0700
Subject: [ATM] ATM: Re: Focal point spot-
In-Reply-To: <003301c9b9ee$9946f890$cbd4e9b0$@com>
References: <DFF5D37F41BB4E4D8C334B1641880F78@R101>
	<003301c9b9ee$9946f890$cbd4e9b0$@com>
Message-ID: <B71103A6B55D4A518BBF8837C953E782@MRBNOTEBOOK>

I thank you all for the insight into this issue. It's funny, each of you has
a slightly different interpretation of my question and the wonderful part
is, that once the entire tapestry is woven together of all the answers, I
find I have my original question answered and several questions answered
that I did not even know were important!

Berthold actually won the prize for the exact interpretation, but everyone
else's answers threw open the door or more complete understanding.

So the next step is to toss in a bino-viewer. Why does that wreak such havoc
on OTA length. I know my DENK IIs include an OCS lens system which
effectively throws the focal plane back farther out. 

Hmmm...did I just answer my own question? Since the bino-viewer unit puts
the eyepieces further out, then you need a shorter OTA or a corrector like
the DENK OCS to move the focal plane?

Am I learning yet?

Jack Swaton
www.StarryHost.com

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Berthold Hamburger
Sent: Friday, April 10, 2009 8:11 AM
To: atm at atmlist.net
Subject: Re: [ATM] ATM: Re: Focal point spot-

I think he asks where the focal plane is formed "geographically" along the
light path.
To my understanding the rays converge in a focal plane at the field stop of
the eyepiece and leave the eyepiece in a parallel manner to form what we
call the airy disc which is projected on the retina.

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 stainless_steel at suddenlink.net
> Sent: viernes, 10 de abril de 2009 17:00
> To: ATM list
> Subject: [ATM] ATM: Re: Focal point spot-
> 
> Jack,
> 
> Many amateurs do not have a clear concept that the focal plane is not a
> point; this is the case only for a single star in the field of view. The
> focal PLANE us what you want to find; to this, you would add the focal
> length of your longest eyepiece (longest focal length eyepiece)- a very
> lucid discussion of the concept off the way an image is built up in the
> focal plane can be found in my treatise, here:
> 
> http://www.atmsite.org/contrib/Harbour/Foucault.html
> 
> I have included this discussion of the focal plane, and the mechanics of
> how
> an image is formed across the entire focal plane because beginners often
> have the erroneous notion, due to incomple illustrations in books, that
> there is only a focal POINT. This is, of course, an entirely erroneous
> concept.
> 
> LZ-130
> (Davey)
> 
> >Where is the focal point of a path of light? For instance, if I were to
> >build a refractor (or newt for that matter) and I were to trace the
> rays
> >from the outside edge of the objective down to the converged focal
> point
> >(say 500mm), what does that converged point represent?  Is that they
> top of
> >the eyepiece? Is that some point inside the focuser? Is it some point
> >inside
> >the eyepiece?
> 
> >I'd like to build a folded refractor, but the question is relevant to a
> >number of projects.
> 
> >Thanks,
> >Jack Swaton
> www.StarryHost.com
> 
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/

_______________________________________________
ATM mailing list http://www.atmlist.net/


From b-hamburger at ya.com  Sat Apr 11 22:45:38 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Sat, 11 Apr 2009 15:45:38 +0200
Subject: [ATM] ATM: Re: Focal point spot-
In-Reply-To: <B71103A6B55D4A518BBF8837C953E782@MRBNOTEBOOK>
References: <DFF5D37F41BB4E4D8C334B1641880F78@R101>
	<003301c9b9ee$9946f890$cbd4e9b0$@com>
	<B71103A6B55D4A518BBF8837C953E782@MRBNOTEBOOK>
Message-ID: <00d601c9baab$ccf9d9b0$66ed8d10$@com>

Exactly. It is the reverse phenomenon from prime focus photography, where
you need significantly more in travel of the focuser. This is why I always
favored sliding focusers, as they accommodate so many different
configurations.

Berthold

-- 
Berthold Hamburger - Cellist/Spain
Email: behambu at artinso.com
http://www.artinso.com
http://www.astro.artinso.com


> -----Original Message-----
> From: Jack Swaton @ Starry Host [mailto:jack.swaton at starryhost.com]
> Sent: s?bado, 11 de abril de 2009 15:23
> To: 'Berthold Hamburger'; atm at atmlist.net
> Subject: RE: [ATM] ATM: Re: Focal point spot-
> 
> I thank you all for the insight into this issue. It's funny, each of you
> has
> a slightly different interpretation of my question and the wonderful
> part
> is, that once the entire tapestry is woven together of all the answers,
> I
> find I have my original question answered and several questions answered
> that I did not even know were important!
> 
> Berthold actually won the prize for the exact interpretation, but
> everyone
> else's answers threw open the door or more complete understanding.
> 
> So the next step is to toss in a bino-viewer. Why does that wreak such
> havoc
> on OTA length. I know my DENK IIs include an OCS lens system which
> effectively throws the focal plane back farther out.
> 
> Hmmm...did I just answer my own question? Since the bino-viewer unit
> puts
> the eyepieces further out, then you need a shorter OTA or a corrector
> like
> the DENK OCS to move the focal plane?
> 
> Am I learning yet?
> 
> Jack Swaton
> www.StarryHost.com
> 
> -----Original Message-----
> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf
> Of
> Berthold Hamburger
> Sent: Friday, April 10, 2009 8:11 AM
> To: atm at atmlist.net
> Subject: Re: [ATM] ATM: Re: Focal point spot-
> 
> I think he asks where the focal plane is formed "geographically" along
> the
> light path.
> To my understanding the rays converge in a focal plane at the field stop
> of
> the eyepiece and leave the eyepiece in a parallel manner to form what we
> call the airy disc which is projected on the retina.
> 
> 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 stainless_steel at suddenlink.net
> > Sent: viernes, 10 de abril de 2009 17:00
> > To: ATM list
> > Subject: [ATM] ATM: Re: Focal point spot-
> >
> > Jack,
> >
> > Many amateurs do not have a clear concept that the focal plane is not
> a
> > point; this is the case only for a single star in the field of view.
> The
> > focal PLANE us what you want to find; to this, you would add the focal
> > length of your longest eyepiece (longest focal length eyepiece)- a
> very
> > lucid discussion of the concept off the way an image is built up in
> the
> > focal plane can be found in my treatise, here:
> >
> > http://www.atmsite.org/contrib/Harbour/Foucault.html
> >
> > I have included this discussion of the focal plane, and the mechanics
> of
> > how
> > an image is formed across the entire focal plane because beginners
> often
> > have the erroneous notion, due to incomple illustrations in books,
> that
> > there is only a focal POINT. This is, of course, an entirely erroneous
> > concept.
> >
> > LZ-130
> > (Davey)
> >
> > >Where is the focal point of a path of light? For instance, if I were
> to
> > >build a refractor (or newt for that matter) and I were to trace the
> > rays
> > >from the outside edge of the objective down to the converged focal
> > point
> > >(say 500mm), what does that converged point represent?  Is that they
> > top of
> > >the eyepiece? Is that some point inside the focuser? Is it some point
> > >inside
> > >the eyepiece?
> >
> > >I'd like to build a folded refractor, but the question is relevant to
> a
> > >number of projects.
> >
> > >Thanks,
> > >Jack Swaton
> > www.StarryHost.com
> >
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From b-hamburger at ya.com  Sat Apr 11 23:53:48 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Sat, 11 Apr 2009 16:53:48 +0200
Subject: [ATM] ATM: Re: Focal point spot-
In-Reply-To: <00d601c9baab$ccf9d9b0$66ed8d10$@com>
References: <DFF5D37F41BB4E4D8C334B1641880F78@R101>	<003301c9b9ee$9946f890$cbd4e9b0$@com>	<B71103A6B55D4A518BBF8837C953E782@MRBNOTEBOOK>
	<00d601c9baab$ccf9d9b0$66ed8d10$@com>
Message-ID: <00da01c9bab5$53036c70$f90a4550$@com>

Oops. It's not the reverse phenomenon. It is exactly the same. Sorry, I got
my directions mixed up.

Berthold

-- 
Berthold Hamburger - Cellist/Spain
Email: behambu at artinso.com
http://www.artinso.com
http://www.astro.artinso.com


> -----Original Message-----
> From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf
> Of Berthold Hamburger
> Sent: s?bado, 11 de abril de 2009 15:46
> To: atm at atmlist.net
> Subject: Re: [ATM] ATM: Re: Focal point spot-
> 
> Exactly. It is the reverse phenomenon from prime focus photography,
> where
> you need significantly more in travel of the focuser. This is why I
> always
> favored sliding focusers, as they accommodate so many different
> configurations.
> 
> Berthold
> 
> --
> Berthold Hamburger - Cellist/Spain
> Email: behambu at artinso.com
> http://www.artinso.com
> http://www.astro.artinso.com
> 
> 
> > -----Original Message-----
> > From: Jack Swaton @ Starry Host [mailto:jack.swaton at starryhost.com]
> > Sent: s?bado, 11 de abril de 2009 15:23
> > To: 'Berthold Hamburger'; atm at atmlist.net
> > Subject: RE: [ATM] ATM: Re: Focal point spot-
> >
> > I thank you all for the insight into this issue. It's funny, each of
> you
> > has
> > a slightly different interpretation of my question and the wonderful
> > part
> > is, that once the entire tapestry is woven together of all the
> answers,
> > I
> > find I have my original question answered and several questions
> answered
> > that I did not even know were important!
> >
> > Berthold actually won the prize for the exact interpretation, but
> > everyone
> > else's answers threw open the door or more complete understanding.
> >
> > So the next step is to toss in a bino-viewer. Why does that wreak such
> > havoc
> > on OTA length. I know my DENK IIs include an OCS lens system which
> > effectively throws the focal plane back farther out.
> >
> > Hmmm...did I just answer my own question? Since the bino-viewer unit
> > puts
> > the eyepieces further out, then you need a shorter OTA or a corrector
> > like
> > the DENK OCS to move the focal plane?
> >
> > Am I learning yet?
> >
> > Jack Swaton
> > www.StarryHost.com
> >
> > -----Original Message-----
> > From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On
> Behalf
> > Of
> > Berthold Hamburger
> > Sent: Friday, April 10, 2009 8:11 AM
> > To: atm at atmlist.net
> > Subject: Re: [ATM] ATM: Re: Focal point spot-
> >
> > I think he asks where the focal plane is formed "geographically" along
> > the
> > light path.
> > To my understanding the rays converge in a focal plane at the field
> stop
> > of
> > the eyepiece and leave the eyepiece in a parallel manner to form what
> we
> > call the airy disc which is projected on the retina.
> >
> > 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 stainless_steel at suddenlink.net
> > > Sent: viernes, 10 de abril de 2009 17:00
> > > To: ATM list
> > > Subject: [ATM] ATM: Re: Focal point spot-
> > >
> > > Jack,
> > >
> > > Many amateurs do not have a clear concept that the focal plane is
> not
> > a
> > > point; this is the case only for a single star in the field of view.
> > The
> > > focal PLANE us what you want to find; to this, you would add the
> focal
> > > length of your longest eyepiece (longest focal length eyepiece)- a
> > very
> > > lucid discussion of the concept off the way an image is built up in
> > the
> > > focal plane can be found in my treatise, here:
> > >
> > > http://www.atmsite.org/contrib/Harbour/Foucault.html
> > >
> > > I have included this discussion of the focal plane, and the
> mechanics
> > of
> > > how
> > > an image is formed across the entire focal plane because beginners
> > often
> > > have the erroneous notion, due to incomple illustrations in books,
> > that
> > > there is only a focal POINT. This is, of course, an entirely
> erroneous
> > > concept.
> > >
> > > LZ-130
> > > (Davey)
> > >
> > > >Where is the focal point of a path of light? For instance, if I
> were
> > to
> > > >build a refractor (or newt for that matter) and I were to trace the
> > > rays
> > > >from the outside edge of the objective down to the converged focal
> > > point
> > > >(say 500mm), what does that converged point represent?  Is that
> they
> > > top of
> > > >the eyepiece? Is that some point inside the focuser? Is it some
> point
> > > >inside
> > > >the eyepiece?
> > >
> > > >I'd like to build a folded refractor, but the question is relevant
> to
> > a
> > > >number of projects.
> > >
> > > >Thanks,
> > > >Jack Swaton
> > > www.StarryHost.com
> > >
> > >
> > > _______________________________________________
> > > ATM mailing list http://www.atmlist.net/
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From vorblesnak at peak.org  Sun Apr 12 02:00:23 2009
From: vorblesnak at peak.org (vorblesnak at peak.org)
Date: Sat, 11 Apr 2009 10:00:23 -0700 (PDT)
Subject: [ATM] Variations on sagitta due to slumping
Message-ID: <3204.69.59.200.230.1239469223.squirrel@webmail.peak.org>

Up to this point I had slumped into a sand bed. The curve was screeded in
with a piece of wood made with a curve cut and sanded to the ROC. This
screed was made using a tape measure to scribe the curve on the wood and
then the wood was cut. The sand bed was the exact diameter of the glass.

Because of the big project and the many foam and puck blanks to be sent
out I began to explore making a hard reusable mold. I made this mold in
the same general way. A mold diameter was chosen, a screed was made with
the required ROC and the curve was screeded onto the wet mold material. I
then "tuned" the surface with sand paper and ceramic slip to make it as
smooth as possible.

Now the weirdness. I will use the 28 inch plate as an example but the same
thing has affected the small plates.

The 28 should be an f3, or 84 inch focal length. The sagitta by
calculation is 18.6 32nds deep. Or in practice 19/32, (0.583").

Experience has taught me to make my molds a couple of inches wider than
the glass so there is mold material under the edge of the glass
regardless. So the mold for the 28 should be around 30 inches in diameter.
I used 32 inches just to be sure. Since screeding is very coarse I chose a
90 inch ROC for the curve of the screed and figured by the time I got it
all smoothed out the curve of the mold would be on the fat side of 84
inches but less than 90 inches. The mold for the small pucks was made in
the same way.

So! After slumping I measured the sagitta of the 28 inch and found about
3/4" of depth. This yielded a focal length of about 65 inches or an f2.3
mirror. Double checked it, checked the screed, checked the mold, 3/4 inch
of sagitta. I decided I had not scribed the right curve and based on the
focal length I must have used 130 inches not 180. I mean, surely if the
mold has a 90 inch focal length, the glass slumped on that mold should
have the same focal length .. right? No! The ROC of the curve scribed onto
the screed was 180 inches and it is time for some math.

Sagitta is a ratio of the radius of the disk squared to twice the radius
of curvature. A 32 inch disk with a 90 inch focal length yields a sagitta
of 0.711. If you put that sagittal depth into a smaller mirror, say a 28
inch, you will have a focal length of about 69 inches. It is the curve of
the disk that is important, not the focal length. And the focal length
will not translate across the same sagitta. 90 on the mold does not mean
90 on the smaller finished disk. It was sizing up the mold that caused the
problem. Nor can I just screed the over sized mold with a 28 inch f3 ROC
screed.

Given an ROC of 168 on a 32 inch disk yields a sagitta of 0.76". That
would give me a focal length on the 28 inch disk of about 64 inches.

To make the curve correct I have to calculate the sagitta for a 28" f3
disk and divide that sagitta into the squared radius of the larger disk.
That will force the correct sagitta on the larger disk and yield the
correct curve to the mold. The resulting ROC is about 1.3 larger than the
target.

Another wrinkle in the brain.

David Davis
Toledo, OR 97391




From holmmarkd at gmail.com  Sun Apr 12 02:16:28 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Sat, 11 Apr 2009 13:16:28 -0400
Subject: [ATM] Sources of Hydrostone in Europe and Australia
In-Reply-To: <142415079.20090411130126@foucault.co.uk>
References: <49DFFB7C.6020307@gmail.com>	<Pine.LNX.4.44.0904111247200.765-100000@uno.canit.se>
	<142415079.20090411130126@foucault.co.uk>
Message-ID: <49E0D06C.603@gmail.com>

Europeans should put US Gypsum products such as Hydrostone out of their 
minds, and look instead for Crystacal Alpha K, Crystacast or any of the 
dental stone products mentioned below from BPB Formula / Saint Gobain 
Formula.

Examination of data sheets shows that Crystacast is perhaps not quite as 
strong as Hydrostone, but it has similar working times.  
http://www.saintgobainformula.com/PDF/EN/CRYSTACAST-ENGLISH.PDF

BPB Formula also have a product Crystacal Alpha K.  Examination of its 
data sheet shows compressive strength a bit higher than Hydrostone and a 
bit longer working time as well.  It might be a good bet for larger 
tools.  http://www.saintgobainformula.com/PDF/EN/CRYSTACALALPHAK-ENGLISH.PDF

It appears that the company BPB Formula may also be known as Saint 
Gobain Formula.

BPB Formula / Saint Gobain Formula also make dental plasters and stones. 
http://www.saintgobainformula.com/en/content-3-21.aspx  It appears that 
the products Pro Solid, Pro Solid Super, Crownstone, Matrix, and Pro 
Rock may all be similar to dental stone products that have been 
successfully used to make grinding tools.

For reference the data sheet for Hydrostone is at 
http://gypsumsolutions.com/search_details_lit.asp?DocId=518


As I mentioned before Hydrostone appears to be available in Australia

In Australia, one dealer for Hydrostone is Barnes Online 
http://www.barnesonline.com.au/productsByCategory.asp?intCatalogID=15&strCatalog_NAME=Gypsums%2C+Plasters+%26+Allied+Products 
<http://www.barnesonline.com.au/productsByCategory.asp?intCatalogID=15&strCatalog_NAME=Gypsums%2C+Plasters+%26+Allied+Products> 


53 King Street

Newtown NSW 2042

Store Phone No: (02) 9557 9056

All technical enquiries call Head Office on 1300 731 497

40 - 42 Swan Street

Richmond VIC 3121

Ph:  (03) 9428 5511

Fax: (03) 9428 5533

USG have  offices at

USG Australasia.

New Zealand

Regional Head Office

PO Box 11-155

Ellerslie 1542

373 Neilson St

Penrose 1061

Auckland

New Zealand

And also at the following Australia locations

        	Queensland    		NSW     	Victoria

Phone n?:    	(07) 3852 5937     (02) 8850 3935     (03) 9639 0900

Fax n?:		(07) 3852 5758     (02) 9659 9292     (03) 9639 0198

Mobile n?:    	 0411 509 650       0402 093 001       0434 561 273

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From ed1234 at cox.net  Sun Apr 12 04:27:53 2009
From: ed1234 at cox.net (Ed D.)
Date: Sat, 11 Apr 2009 15:27:53 -0400
Subject: [ATM] Variations on sagitta due to slumping
References: <3204.69.59.200.230.1239469223.squirrel@webmail.peak.org>
Message-ID: <5DFD3B85E6984970A3FBFA4515A04957@HomeDesktop>

Dave regardless of the diameter of the sand mold 28", 30", 32" or more you
would still use a screed with a 168" radius cut into it so that the 28" 
glass will
have the desired f3 84" focal length. The only other fine tuning you may 
want
to think about is compensating for the thickness of the glass for example 
1/8
inch thick glass you would make the screed 168.125" and for 1/4 inch thick
glass 168.250" and so on. Not that a 1/8" or even 1/4" on radius this large
makes a big difference. My two cents

Take care
   Ed...........

----- Original Message ----- 
From: <vorblesnak at peak.org>
To: <atm at atmlist.net>
Sent: Saturday, April 11, 2009 1:00 PM
Subject: [ATM] Variations on sagitta due to slumping


> Up to this point I had slumped into a sand bed. The curve was screeded in
> with a piece of wood made with a curve cut and sanded to the ROC. This
> screed was made using a tape measure to scribe the curve on the wood and
> then the wood was cut. The sand bed was the exact diameter of the glass.
>
> Because of the big project and the many foam and puck blanks to be sent
> out I began to explore making a hard reusable mold. I made this mold in
> the same general way. A mold diameter was chosen, a screed was made with
> the required ROC and the curve was screeded onto the wet mold material. I
> then "tuned" the surface with sand paper and ceramic slip to make it as
> smooth as possible.
>
> Now the weirdness. I will use the 28 inch plate as an example but the same
> thing has affected the small plates.
>
> The 28 should be an f3, or 84 inch focal length. The sagitta by
> calculation is 18.6 32nds deep. Or in practice 19/32, (0.583").
>
> Experience has taught me to make my molds a couple of inches wider than
> the glass so there is mold material under the edge of the glass
> regardless. So the mold for the 28 should be around 30 inches in diameter.
> I used 32 inches just to be sure. Since screeding is very coarse I chose a
> 90 inch ROC for the curve of the screed and figured by the time I got it
> all smoothed out the curve of the mold would be on the fat side of 84
> inches but less than 90 inches. The mold for the small pucks was made in
> the same way.
>
> So! After slumping I measured the sagitta of the 28 inch and found about
> 3/4" of depth. This yielded a focal length of about 65 inches or an f2.3
> mirror. Double checked it, checked the screed, checked the mold, 3/4 inch
> of sagitta. I decided I had not scribed the right curve and based on the
> focal length I must have used 130 inches not 180. I mean, surely if the
> mold has a 90 inch focal length, the glass slumped on that mold should
> have the same focal length .. right? No! The ROC of the curve scribed onto
> the screed was 180 inches and it is time for some math.
>
> Sagitta is a ratio of the radius of the disk squared to twice the radius
> of curvature. A 32 inch disk with a 90 inch focal length yields a sagitta
> of 0.711. If you put that sagittal depth into a smaller mirror, say a 28
> inch, you will have a focal length of about 69 inches. It is the curve of
> the disk that is important, not the focal length. And the focal length
> will not translate across the same sagitta. 90 on the mold does not mean
> 90 on the smaller finished disk. It was sizing up the mold that caused the
> problem. Nor can I just screed the over sized mold with a 28 inch f3 ROC
> screed.
>
> Given an ROC of 168 on a 32 inch disk yields a sagitta of 0.76". That
> would give me a focal length on the 28 inch disk of about 64 inches.
>
> To make the curve correct I have to calculate the sagitta for a 28" f3
> disk and divide that sagitta into the squared radius of the larger disk.
> That will force the correct sagitta on the larger disk and yield the
> correct curve to the mold. The resulting ROC is about 1.3 larger than the
> target.
>
> Another wrinkle in the brain.
>
> David Davis
> Toledo, OR 97391
>
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/ 


From thomas at moiler.com  Sun Apr 12 06:55:45 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Sun, 12 Apr 2009 07:55:45 +1000
Subject: [ATM] Variations on sagitta due to slumping
In-Reply-To: <3204.69.59.200.230.1239469223.squirrel@webmail.peak.org>
References: <3204.69.59.200.230.1239469223.squirrel@webmail.peak.org>
Message-ID: <00e301c9baf0$45e2d220$d1a87660$@com>

I would suggest using a slightly different molding material. Namely
"Potter's Plaster", screed your sand mold as per normal and then give it a
plaster wash with a very runny plaster mix, then re-screed to smooth out any
damage from pouring the plaster.

This plaster is designed to be used as a high temp mold material and
although it does shrink a little (SO2 is released) when fired it doesn't
warp. 

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
vorblesnak at peak.org
Sent: Sunday, 12 April 2009 3:00 AM
To: atm at atmlist.net
Subject: [ATM] Variations on sagitta due to slumping

Up to this point I had slumped into a sand bed. The curve was screeded in
with a piece of wood made with a curve cut and sanded to the ROC. This
screed was made using a tape measure to scribe the curve on the wood and
then the wood was cut. The sand bed was the exact diameter of the glass.

Because of the big project and the many foam and puck blanks to be sent
out I began to explore making a hard reusable mold. I made this mold in
the same general way. A mold diameter was chosen, a screed was made with
the required ROC and the curve was screeded onto the wet mold material. I
then "tuned" the surface with sand paper and ceramic slip to make it as
smooth as possible.

Now the weirdness. I will use the 28 inch plate as an example but the same
thing has affected the small plates.

The 28 should be an f3, or 84 inch focal length. The sagitta by
calculation is 18.6 32nds deep. Or in practice 19/32, (0.583").

Experience has taught me to make my molds a couple of inches wider than
the glass so there is mold material under the edge of the glass
regardless. So the mold for the 28 should be around 30 inches in diameter.
I used 32 inches just to be sure. Since screeding is very coarse I chose a
90 inch ROC for the curve of the screed and figured by the time I got it
all smoothed out the curve of the mold would be on the fat side of 84
inches but less than 90 inches. The mold for the small pucks was made in
the same way.

So! After slumping I measured the sagitta of the 28 inch and found about
3/4" of depth. This yielded a focal length of about 65 inches or an f2.3
mirror. Double checked it, checked the screed, checked the mold, 3/4 inch
of sagitta. I decided I had not scribed the right curve and based on the
focal length I must have used 130 inches not 180. I mean, surely if the
mold has a 90 inch focal length, the glass slumped on that mold should
have the same focal length .. right? No! The ROC of the curve scribed onto
the screed was 180 inches and it is time for some math.

Sagitta is a ratio of the radius of the disk squared to twice the radius
of curvature. A 32 inch disk with a 90 inch focal length yields a sagitta
of 0.711. If you put that sagittal depth into a smaller mirror, say a 28
inch, you will have a focal length of about 69 inches. It is the curve of
the disk that is important, not the focal length. And the focal length
will not translate across the same sagitta. 90 on the mold does not mean
90 on the smaller finished disk. It was sizing up the mold that caused the
problem. Nor can I just screed the over sized mold with a 28 inch f3 ROC
screed.

Given an ROC of 168 on a 32 inch disk yields a sagitta of 0.76". That
would give me a focal length on the 28 inch disk of about 64 inches.

To make the curve correct I have to calculate the sagitta for a 28" f3
disk and divide that sagitta into the squared radius of the larger disk.
That will force the correct sagitta on the larger disk and yield the
correct curve to the mold. The resulting ROC is about 1.3 larger than the
target.

Another wrinkle in the brain.

David Davis
Toledo, OR 97391



_______________________________________________
ATM mailing list http://www.atmlist.net/


From holmmarkd at gmail.com  Sun Apr 12 10:14:35 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Sat, 11 Apr 2009 21:14:35 -0400
Subject: [ATM] More about BPB Formula / Saint Gobain Formula plaster
 products for mirror grinding tools
Message-ID: <49E1407B.9040702@gmail.com>

I have spent a little time going through technical data sheets for 
various products from BPB Formula  /  Saint Gobain Formula.  These 
products should be available in many parts of Europe.

Most of the products do not specifically call out resistance to outdoor 
or high humidity environments.  (Note: neither does USG Hydrostone, but 
it works well for tools anyhow.)

Two BPB Formula  /  Saint Gobain Formula products do:

The data sheet for Hobbygips H says, "This product is used to produce 
very detailed extra hard models, giftware models and reliefs suitable 
for external use."  (My reading of the other product data sheets 
indicates that "external" means outdoor.)

The data sheet for  Hobbygips Plus says, "Hobbygips Plus provides high 
resistance to chlorinated humidity (Essen University Test Centre 
certification) and is suited for casting freestanding decorative items 
for humid interiors, including swimming pool hall areas. No guarantee 
can be given concerning product aptitude for building or architectural 
applications, or applications involving constant exposure to water as 
the product was not designed or tested for this use."

The data sheets are at:

http://www.saintgobainformula.com/PDF/EN/HOBBYGIPSH-ENGLISH.PDF

http://www.saintgobainformula.com/PDF/EN/HobbygipsPlus-English.pdf


My conclusion is that perhaps Hobbygips H should be the product of 
choice for mirror grinding tools and polishing lap back plates.  Note 
that, at this time, we have no reports from atm's using any of the BPB 
Formula products for these purposes.  All my recomendations are based on 
reading the data sheets.  Also see previous posts titled "Sources of 
Hydrostone in Europe and Australia" and "Re: [ATM] Sources of Hydrostone 
in Europe and Australia"


Addresses for BPB Formula are:

UK
BPB Formula
Newark Works
Bowbridge Lane
Nottinghamshire
NG24 3BZ

Tel: +44 (0) 1636 670249
Fax: +44 (0) 1636 670229

formula.marketing at bpb.com

France
BPB Formula
34, avenue Franklin Roosevelt
92282 Suresnes Cedex

Tel: +33 (0) 1 46 25 46 15
Fax: +33 (0) 1 46 25 46 90

formula at bpb.fr

Germany
BPB Formula GmbH
Kutzh?tte
D-37455 Walkenried

Tel: +49 (0) 5525 203-0
Fax: +49 (0) 5525 551

info at bpbformula.de

Spain
BPB Formula
C/Albacete 5? - 6? Planta
28027 Madrid

Tel: +34 (9) 1 326 4932
Fax: +34 (9) 1 403 660

formula.marketing at bpb.com

Romania
BPB Formula
22 Decembrie 1989
str. F. N
Turda -3350- Jud. CLUJ

Tel: +40 (0) 64 31 46 16
Fax: +40 (0) 64 31 67 94

gypsum at mail.dntcj.ro

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From holmmarkd at gmail.com  Sun Apr 12 10:31:13 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Sat, 11 Apr 2009 21:31:13 -0400
Subject: [ATM] Another supplier of USG Hydrostone and dental stone in
 Australia
Message-ID: <49E14461.9060307@gmail.com>

Dalchem carries the USG line of plaster products useful for mirror 
grinding tool making.  (Their web site hasn't been working terribly well 
for me.)

http://www.dalchem.com.au/index.php?option=com_content&task=view&id=97&Itemid=113


Dalchem
Telephone: 03 9553 7040
Fax: 03 9553 2407
sales at dalchem.com.au <mailto:sales at dalchem.com.au> This e-mail address 
is being protected from spam bots, you need JavaScript enabled to view it
141 Herald Street, Cheltenham, Victoria, Australia. 3192 
<http://www.dalchem.com.au/index.php?option=com_content&task=view&id=201>

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From arjan.te.marvelde at hetnet.nl  Sun Apr 12 17:46:40 2009
From: arjan.te.marvelde at hetnet.nl (Arjan te Marvelde (hetnet))
Date: Sun, 12 Apr 2009 10:46:40 +0200
Subject: [ATM] The reason for this list..
Message-ID: <49E1AA70.40106@hetnet.nl>

Berthold,

To what extent is this group specific about Mels' system?

Quoting the Yahoo scope-drive group page:
"Description:
This mailinglist is a forum to discuss topics related to Mel Bartels' 
computerized telescope control system"

Cheers,
   Arjan


 >>>

Done. Anybody else who wants to join can just go to
http://tech.groups.yahoo.com/group/scope-drive

Berthold

<<<

From b-hamburger at ya.com  Sun Apr 12 18:26:35 2009
From: b-hamburger at ya.com (Berthold Hamburger)
Date: Sun, 12 Apr 2009 11:26:35 +0200
Subject: [ATM] [SPAM DETECT] Re:  The reason for this list..
In-Reply-To: <49E1AA70.40106@hetnet.nl>
References: <49E1AA70.40106@hetnet.nl>
Message-ID: <012d01c9bb50$c792e340$56b8a9c0$@com>

Hi Arjan,

Most people on the list use some form or variation of Mels' system. However
that does not mean that the group is limited to it. As on the ATM list there
is a vast knowledge about control mechanisms, mechanical and computational,
available on our list. If you want to go down another path then Mels' system
we will be more than happy to welcome you and add your knowledge to the hive
;-)

Berthold

-- 
Berthold Hamburger - Cellist/Spain
Email: behambu at artinso.com
http://www.artinso.com
http://www.astro.artinso.com


> -----Original Message-----
> From: Arjan te Marvelde (hetnet) [mailto:arjan.te.marvelde at hetnet.nl]
> Sent: domingo, 12 de abril de 2009 10:47
> To: atm at atmlist.net; b-hamburger at ya.com
> Subject: [SPAM DETECT] Re: [ATM] The reason for this list..
> 
> Berthold,
> 
> To what extent is this group specific about Mels' system?
> 
> Quoting the Yahoo scope-drive group page:
> "Description:
> This mailinglist is a forum to discuss topics related to Mel Bartels'
> computerized telescope control system"
> 
> Cheers,
>    Arjan
> 
> 
>  >>>
> 
> Done. Anybody else who wants to join can just go to
> http://tech.groups.yahoo.com/group/scope-drive
> 
> Berthold
> 
> <<<


From gfbrandenburg at yahoo.com  Mon Apr 13 08:15:33 2009
From: gfbrandenburg at yahoo.com (Guy Brandenburg)
Date: Sun, 12 Apr 2009 16:15:33 -0700 (PDT)
Subject: [ATM] Mounting inexpensive 52 mm diam achromatic objectives in 2
	inch PVC pipe.
Message-ID: <663087.18104.qm@web111508.mail.gq1.yahoo.com>


Hi, Julie,

I went up to Surplus Shed yesterday and bought 24 achromatic objective lenses, 52 mm diameter, 220 mm focal length, not coated, $6 each. I also bought 24  12 mm eyepieces (that's the FL) and 24 20 mm eyepieces; they are .965 inches diameter (25 mm). I also bought four simple biconvex objective lenses, a bit smaller diameter, and four simple biconcave eyepiece lenses, smaller diameter still, so kids can see what Galileo had to contend with. The eyepieces were less than $4 each. The staff there was quite interested in the project and thought it was a good idea. The total cost was about $330, or roughly $13 per telescope so far. The drive was 3 hours each way.

I think I've figured out a way to mount the achromatic objective lenses in the refractors. They won't quite fit inside 2 inch PVC pipe, (because that's only 50.8 mm, and the extra 1.2 mm does make a difference). The objective lenses that they had up there that would have fit nicely had other objectionable qualities (bad optics, or they only had a few, or the two elements weren't cemented together, or were too expensive), so I am glad I went to see for myself. I had to hand-pick the ones that had the fewest dings and cementing problems.

I was trying to figure out how to ream out PVC pipe nicely by the extra 1.2 mm or so, in order the students wouldn't have to do that. (After all, they are only middle schoolers and not terribly dextrous. Heck, I don't know how I could ream them out myself by hand, especially since the reaming has to be absolutely perpendicular to the axis of the scope!

Here's my plan. I get a 4 foot length of 2 inch PVC, whatever length. Use a wood lathe to cut two cylinders of wood with exactly 2 inch diameters. One of them gets a tapered hole in one end. The cylinders are pushed snugly into each end. The end with a pure wooden cylinder end is put into the chuck (3 or 4 jaw, no matter), flush to the end of the pipe. The wooden cylinder with the tapered hole gets put into the other end, pushed in perhaps an inch or so, and the center on the toolstock goes into there. I then use some sort of boring bit to enlarge the diameter of that end by a little more than one millimeter. Then I use a cutoff bit to cut off and save about two inches of PVC stock. Then I push the cylinder down another inch and repeat, 24 times. Since PVC is soft (unlike aluminum or steel) then this should go fairly quickly, I hope.

These small, nominally 2 inch ID pieces (but now 52 or 52.5 mm ID pieces) of PVC should work perfectly for mounting the objective lenses. I think. Then other pieces of PVC or cardboard can be used to make it so that the cheapo .965 eyepieces can be mounted and 'telescoped' to come to a focus. The .965 eyepieces will only need a few layers of ordinary masking tape for them to fit perfectly inside 1 inch PVC pipe.

One of the main problems we'll have, I think, is trying to figure out how the students can paint them! Ordinary water-soluble paints won't work, I'm sure. Even alkyd or oil-based paints might have some difficulty. We might need to have the students (or us) roughen them up with emery paper so that anything at all, even a primer, will stick. 

The reason for having little pieces like that is so that students can then use 2 inch to 2 inch junction collars, or else 2 inch to 1+1/2 inch junction collars (which are cheap, less than $1 each), using that weird solvent that plumbers use for that purpose. The only thing I haven't yet figured out is how to link 1+1/2 inch PVC to 1 inch PVC; they didn't have any such collars at the Home Depot on Brentwood/Rhode Island Ave.


Guy Brandenburg, Washington, DC
My home page on astronomy, mathematics, education:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
or else 
http://tinyurl.com/r6fh2

=============================
"Education isn't rocket science. It's much, much harder."
(Author unknown)



      

From gfbrandenburg at yahoo.com  Mon Apr 13 08:16:59 2009
From: gfbrandenburg at yahoo.com (Guy Brandenburg)
Date: Sun, 12 Apr 2009 16:16:59 -0700 (PDT)
Subject: [ATM] Mounting inexpensive 52 mm diam achromatic objectives in
	2 inch PVC pipe.
Message-ID: <278508.86438.qm@web111511.mail.gq1.yahoo.com>


Hey, sorry, I sent that to the wrong person.
Guy


      

From mick at liquidgold.eclipse.co.uk  Mon Apr 13 08:58:52 2009
From: mick at liquidgold.eclipse.co.uk (Mick Dunn)
Date: Mon, 13 Apr 2009 00:58:52 +0100
Subject: [ATM] Jackson 6:1 ball drive
Message-ID: <A3D421BA30A348F3AAF4454645A398FA@lufc501>

Just like to share that recently i took a chance and bought a  Jackson 6:1 ball drive and although i dont have any photos to show you i can assure you that with a small amount of ingenuity these can be adapted to a single speed focuser, i fitted one of these to a 12" Lightbridge and it works a treat,i know they're not 10:1 drives but they're not 10:1 drive prices either i paid just over ?8 delivered for mine there is also a source on the other side of the pond. I used the 4511DAF as it has a large flange.
I searched the archives before posting and didn't find any mention.
Take a look
  http://www.mainlinegroup.co.uk/jacksonbrothers/4511.htm

http://surplussales.com/ShaftHardware/JacksonBro.html

Mick



From atmpob at yahoo.com  Mon Apr 13 10:27:00 2009
From: atmpob at yahoo.com (Dale Eason)
Date: Sun, 12 Apr 2009 18:27:00 -0700 (PDT)
Subject: [ATM] Jackson 6:1 ball drive
In-Reply-To: <A3D421BA30A348F3AAF4454645A398FA@lufc501>
Message-ID: <696429.57642.qm@web54502.mail.re2.yahoo.com>


Here is another good link

http://bedair.org/Focus/focusproject.html


--- On Sun, 4/12/09, Mick Dunn <mick at liquidgold.eclipse.co.uk> wrote:

> From: Mick Dunn <mick at liquidgold.eclipse.co.uk>
> Subject: [ATM] Jackson 6:1 ball drive
> To: atm at atmlist.net
> Date: Sunday, April 12, 2009, 6:58 PM
> Just like to share that recently i took a chance and bought
> a  Jackson 6:1 ball drive and although i dont have any
> photos to show you i can assure you that with a small amount
> of ingenuity these can be adapted to a single speed focuser,



      

From rmay at nethere.com  Tue Apr 14 06:12:33 2009
From: rmay at nethere.com (Bob May)
Date: Mon, 13 Apr 2009 14:12:33 -0700
Subject: [ATM] Mounting inexpensive 52 mm diam achromatic objectives in
	2inch PVC pipe.
References: <663087.18104.qm@web111508.mail.gq1.yahoo.com>
Message-ID: <000601c9bc7c$917b18e0$8f78fea9@amd>

Many things you can do to get the objectives to fit.  One is to
use a junction piece to hold a short piece of bored pipe.  For
this, cut a piece that will just fit inside the junction and
maybe enough to hang out for a sun shield if desired.  Turn the
inside to the desired diameter - the piece is short so you won't
be hanging it out of the chuck very far.  Put the glass in and
put the tube in so that the glass is towards the center of the
junction.  If you turn a groove in either of the pieces that go
into the junction to fit over the stop inside of it, you can set
things up so that the glass is exactly captured in the junction
piece.
For the focusing end, I've done sevrral things including reducers
that have been bored to the right dimensins so that they will
slide along nicely.
For the black inside, I've used all kinds of paint including
water based stuff.  For the outise, any of the spray stuff that
is solvent based will work fine.
Another thing that may be of interest is that the PVC will turn
flexible at temps of about boiling water and you can do an
expansion of the plastic to any larger size you desire.  The only
bad thing is that there will be a bit of taper at the end of the
expansion unless you shrink the plastic around the end of the
plug.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From holmmarkd at gmail.com  Tue Apr 14 08:22:38 2009
From: holmmarkd at gmail.com (Mark Holm)
Date: Mon, 13 Apr 2009 19:22:38 -0400
Subject: [ATM] Jackson 6:1 ball drive
In-Reply-To: <A3D421BA30A348F3AAF4454645A398FA@lufc501>
References: <A3D421BA30A348F3AAF4454645A398FA@lufc501>
Message-ID: <49E3C93E.2060709@gmail.com>

How much torque can these things transmit, and how smooth are they?  Any 
chance they could be used as early stages in a scope drive reduction setup?

-- 
Mark Holm
markholm at verizon.net
holmmarkd at gmail.com


From mick at liquidgold.eclipse.co.uk  Tue Apr 14 09:18:14 2009
From: mick at liquidgold.eclipse.co.uk (Mick Dunn)
Date: Tue, 14 Apr 2009 01:18:14 +0100
Subject: [ATM] Jackson 6:1 ball drive
Message-ID: <BBBF27F31207451A90C41A811E32CD70@lufc501>

There pretty smooth  Mark (not as smooth as my Moonlite) and they can be stripped
and re-greased which i imagine will  make them smoother but i haven't felt the 
need.
As for a reduction drive i wouldn't like to say, i don't know how to translate: 
"Torque 175 mNm"   whatever that means, i think it's pretty low considering 
what the are originally made for.

Mick

From atmer at flash.net  Thu Apr 16 12:09:55 2009
From: atmer at flash.net (Anthony Stillman)
Date: Wed, 15 Apr 2009 20:09:55 -0700 (PDT)
Subject: [ATM] waisted bandwidth
Message-ID: <614207.97305.qm@web82004.mail.mud.yahoo.com>


This is a test of the ATM broadcasting system.  Had this been an actually ATM emergency you would be instructed to get back to grinding.

Anthony

From Mitch_Bisnauth at Cknainc.com  Fri Apr 17 00:04:04 2009
From: Mitch_Bisnauth at Cknainc.com (Mitch_Bisnauth at Cknainc.com)
Date: Thu, 16 Apr 2009 10:04:04 -0500
Subject: [ATM] waisted bandwidth
In-Reply-To: <614207.97305.qm@web82004.mail.mud.yahoo.com>
Message-ID: <OF4C9F6C8B.0B5022B4-ON8625759A.0052A22C-8625759A.0052D891@Cknainc.com>

Should I stop polishing....? .... its nice and hyperbolic....:-)
MitchB



Anthony Stillman <atmer at flash.net> 
Sent by: atm-bounces at atmlist.net
04/15/2009 10:09 PM

To
"atm at atmlist.net" <atm at atmlist.net>
cc

Subject
[ATM] waisted bandwidth







This is a test of the ATM broadcasting system.  Had this been an actually 
ATM emergency you would be instructed to get back to grinding.

Anthony
_______________________________________________
ATM mailing list http://www.atmlist.net/


From jkoptic at juno.com  Fri Apr 17 05:50:59 2009
From: jkoptic at juno.com (Jarvis Krumbein)
Date: Thu, 16 Apr 2009 13:50:59 -0700
Subject: [ATM] Jackson 6:1 ball drive
Message-ID: <20090416.135059.1340.0.jkoptic@juno.com>

Mark, these are planetary ball drives and are intended for very low
speed/low torque applications.  They were originally designed as shaft
reducers for radio tuning use, usually turning a variable capacitor. 
They are also designed to slip when the driven shaft is stopped at the
end of travel.  Wear is fairly high under these circumstances so they
probably are not well suited to inclusion in a drive train.

Jarvis Krumbein

On Mon, 13 Apr 2009 19:22:38 -0400 Mark Holm <holmmarkd at gmail.com>
writes:
> How much torque can these things transmit, and how smooth are they?  
> Any 
> chance they could be used as early stages in a scope drive reduction 
> setup?
> 
> -- 
> Mark Holm
> markholm at verizon.net
> holmmarkd at gmail.com
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 

____________________________________________________________
Click to find information on your credit score and your credit report.
http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTIkRpnCToaoptwDr2ga5yIc3xnhscFuKxW7wBk2GjM5tjM7TkeOMw/

From rflrs at rcn.com  Sun Apr 19 07:30:37 2009
From: rflrs at rcn.com (Richard F.L.R. Snashall)
Date: Sat, 18 Apr 2009 18:30:37 -0400
Subject: [ATM] Higher Order Spherical Aberration in a Doublet
Message-ID: <49EA548D.9070304@rcn.com>

When I allow nearly complete freedom (curves and
air-space) in a doublet design, the higher order
spherical aberration can be matched by residual
3rd order.  Occasionally, this is close enough
to an additional geometric constraint that tweaking
the lens thicknesses will exactly match the
constraint.  With the inner radii equal, I have
(80 mm, f/6.25):

    http://users.rcn.com/rflrs/dbl04-44x.atm   ATMOS input file
    http://users.rcn.com/rflrs/dbl04-44x.len   OSLO input file
    http://users.rcn.com/rflrs/dbl04-44x.txt   TEXT prescription
    http://users.rcn.com/rflrs/dbl04-44x.zmx   ZEMAX input file

This lens is aplanatic in the green (e) with canonical
F-C color correction.  If you look closely at the green,
though, not only is the longitudinal error at the edge
close to zero, but there is an additional zone that is
nulled.  Most often that is about the 75% zone, but that
might be due to my particular optimization procedure.

I think this only improves the performance modestly.  I
think the major gain here is that the lens can be tested
at that green line with a good deep null.

The difficulty here is that the design requires an
accurate way to make the 1.08 mm space.  Trying again,
I get (again 80mm, f/6.25):

    http://users.rcn.com/rflrs/dbl04-48x.atm   ATMOS input file
    http://users.rcn.com/rflrs/dbl04-48x.len   OSLO input file
    http://users.rcn.com/rflrs/dbl04-48x.txt   TEXT prescription
    http://users.rcn.com/rflrs/dbl04-48x.zmx   ZEMAX input file

The edge space here is now a quarter millimeter, which
could allow it to be implemented with some sort of
precision shim.

Does anyone know of such an all-spherical achromat
that does not require the shims -- i.e. a contact
doublet that nulls the zonal error?



From vla at copper.net  Sun Apr 19 09:19:36 2009
From: vla at copper.net (vladimir sacek)
Date: Sat, 18 Apr 2009 20:19:36 -0400
Subject: [ATM] Higher Order Spherical Aberration in a Doublet
References: <49EA548D.9070304@rcn.com>
Message-ID: <000a01c9c084$86ff3ca0$504ff804@Handsome>

Richard F.L.R. Snashall wrote:
> 
> Does anyone know of such an all-spherical achromat
> that does not require the shims -- i.e. a contact
> doublet that nulls the zonal error?
> 
If the goal is to eliminate air space, this would do:

(80mm f/6.25 contact doublet with zero separation)

R1/t1,M1/R2:  303.8 / 12.5, BK7 / -180.4
R3/t2.M2/R3: -182.5 / 6.25, F2  / -737.5

The errors in  F and C are nearly equalized. 

Vla

From rflrs at rcn.com  Sun Apr 19 10:10:50 2009
From: rflrs at rcn.com (Richard F.L.R. Snashall)
Date: Sat, 18 Apr 2009 21:10:50 -0400
Subject: [ATM] Higher Order Spherical Aberration in a Doublet
In-Reply-To: <000a01c9c084$86ff3ca0$504ff804@Handsome>
References: <49EA548D.9070304@rcn.com>
	<000a01c9c084$86ff3ca0$504ff804@Handsome>
Message-ID: <49EA7A1A.5060406@rcn.com>

vladimir sacek wrote:
> Richard F.L.R. Snashall wrote:
>>
>> Does anyone know of such an all-spherical achromat
>> that does not require the shims -- i.e. a contact
>> doublet that nulls the zonal error?
>>
> If the goal is to eliminate air space, this would do:
>
> (80mm f/6.25 contact doublet with zero separation)
>
> R1/t1,M1/R2:  303.8 / 12.5, BK7 / -180.4
> R3/t2.M2/R3: -182.5 / 6.25, F2  / -737.5
>
> The errors in  F and C are nearly equalized.
> Vla
That does not eliminate the problem of needing a shim.
To not need the shim, the edge needs to be in contact,
not the center.

Also I have a problem with it meeting the specifications.
It does not appear to be aplanatic in the green, nor does
it have canonical F-C correction.


From vla at copper.net  Sun Apr 19 13:39:19 2009
From: vla at copper.net (vladimir sacek)
Date: Sun, 19 Apr 2009 00:39:19 -0400
Subject: [ATM] Higher Order Spherical Aberration in a Doublet
References: <49EA548D.9070304@rcn.com><000a01c9c084$86ff3ca0$504ff804@Handsome>
	<49EA7A1A.5060406@rcn.com>
Message-ID: <000601c9c0a8$cf685610$d05ff804@Handsome>

Richard Snashall wrote:

> That does not eliminate the problem of needing a shim.
> To not need the shim, the edge needs to be in contact,
> not the center.
>
> Also I have a problem with it meeting the specifications.
> It does not appear to be aplanatic in the green, nor does
> it have canonical F-C correction.
>
No need for shim once the retainer ring brings the lenses together.
It cannot be aplanatic, since it has non-zero higher-order coma. The
one you posted is not aplanatic either, but it does have less coma.
The one I posted has 0.075 wave RMS at ~2.8 degrees off
axis; astigmatism there is 1.4 waves RMS,  making coma entirely
invisible (it even has slightly lower total RMS error than your "aplanat").

Higher-order coma is minimized to 1/5 by balancing with 1.2 times of
lower-order coma of opposite sign. An aplanatic objective would have
to have higher-order coma near cancelled, in addition to the lower-order 
form.

Chromatic correction is pretty close: 0.468 vs. 0.450 wave RMS F/C
average. Nominal secondary spectrum nearly equalizes if the rear lens
thickness increases to 8mm (neither is quite at 1/2000 canonical 
correction).

Vla







From d.sleeter at roadrunner.com  Sun Apr 19 21:09:39 2009
From: d.sleeter at roadrunner.com (David Sleeter)
Date: Sun, 19 Apr 2009 05:09:39 -0700
Subject: [ATM] Followup to: Help with Spectrophotometer Optics Alignment
Message-ID: <000a01c9c0e7$b74d13b0$25e73b10$@sleeter@roadrunner.com>

Hi Folks:

 

On March 30th I posted a message here asking for suggestions on how to align
and focus the mirrors in some small spectrophotometers that I routinely
rebuild. In some of the instruments I receive, the mirror coatings have gone
bad, and after recoating, they have to be reinstalled, refocused, and
realigned. I received some helpful suggestions from several of you, and with
the help of those suggestions and some further reflection, I think I?ve
figured it out. 

 

In part of one of Dominic-Luc?s replies he said:

 

?The instruments I have seen have always had slightly larger gratings than
beam width at the grating, but mirrors can be much larger than grating.
Basic arrangement for monochromators I know of is:

 

slit 1 > mirror 1 > grating > mirror 2 > slit 2?.

 

When I read this, I realized that the instruments I have to realign use a
unique single-beam, double-pass optical arrangement. They use three slits,
and three mirrors in the following order:

 

entrance slit > concave mirror 1 > grating > central slit > central flat
mirror > back out the central slit > grating again > concave mirror 2 > exit
slit.

 

If you replaced the grating with an optical flat, concave mirror 1 would be
adjusted to bring the image of the entrance slit to focus on the surface of
the central flat mirror, and up to this point, the beam from the entrance
slit converges on this goal.

 

>From the central mirror, the beam diverges back out through the central slit
(mounted just in front of the central mirror?s surface), is then reflected
off of concave mirror 2, which brings it to a final focus on the
instrument?s exit slit.

 

Why bring the entrance slit image to focus on the central flat mirror? By
doing so, the central mirror can be tiny (the ones in these instruments are
about ?? square), this results in a more compact optical system than you?d
get with a standard arrangement.

 

Why the third ?central? optical slit? This 3rd slit, mounted halfway through
the beam?s journey from the entrance slit to the exit slit, picks off a tiny
part of the spectrum, reducing stray light, and improving the instrument?s
resolution.

 

To realign and refocus the mirrors, I need a standard rectangular optical
flat of the same dimensions as the grating. For the focus-realignment
procedure, I think I can temporarily install the optical flat, replace the
exit slit with a piece of ground glass, adjust the mirrors to bring the
entrance slit image to focus on the ground glass, then replace the grating
and the exit slit when I?m done. Any comments?

 

David Sleeter

 


From alcom_ny at yahoo.com  Mon Apr 20 10:26:12 2009
From: alcom_ny at yahoo.com (alik alik)
Date: Sun, 19 Apr 2009 18:26:12 -0700 (PDT)
Subject: [ATM] my first mirror
Message-ID: <761172.47151.qm@web50008.mail.re2.yahoo.com>

hi
?perhaps you may answer my questions regarding making my first mirror

i have a 6" pyrex and a 12" plain glass i guess (it has no markings, but it is only 1" thick)

i would like to know what is a differance between an optical flat and a convex mirror, how do i test my blank to determine if they already are optical flat, and so on

can i grind my glass with a tool or do i need a secong glass?

technicaly i do not know anything about telescope making (exept what i have learned from Francis videos on youtube, but unfortunately he jumped from project to project and i got confused) so i was really hopping if somebody could walk me through step by step 

Thanks
Alex


      

From simo at simoivanov.com  Mon Apr 20 11:47:10 2009
From: simo at simoivanov.com (simo ivanov)
Date: Mon, 20 Apr 2009 11:47:10 +0900
Subject: [ATM] OT - test message, please ignore
Message-ID: <49EBE22E.2090601@simoivanov.com>

Test message.

From virgilaj at charter.net  Mon Apr 20 12:27:39 2009
From: virgilaj at charter.net (Virgil.Johnson)
Date: Sun, 19 Apr 2009 20:27:39 -0700
Subject: [ATM] my first mirror
References: <761172.47151.qm@web50008.mail.re2.yahoo.com>
Message-ID: <C309EFB9932D4F68A2597820575854F4@yourxktpas8d47>

Welcome aboard Alex,

Do both of these pieces have a polished surface?

On a convex surface the reflection would look reduced in size like some 
rear-view mirrors on automobiles.
We want a concave surface for making a newtonian telescope primary.

You didn't say how you came to have these pieces. Is there any reason to 
suspect that they are optical flats?
A lot of surfaces may appear flat, but a true optical flat is something you 
would want to keep.

A 12 inch optical flat would probably be thicker than 1 inch.
Does the 12 inch piece have any color to it when looked at from the side?

You can make a tool from tile and plaster. This has been discussed quite a 
bit recently and the archives are a good place to look for answers.

Here is a link to the Stellafane Mirror Making web pages.

http://stellafane.org/tm/atm/index.html

You will find that are many different ways to the end result and will hear 
many opinions.

The one opinion we all share is that you can do this!

Virgil Johnson
Raider of the Lost Dark




From dlwebb at canit.se  Tue Apr 21 01:44:32 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Mon, 20 Apr 2009 18:44:32 +0200 (MET DST)
Subject: [ATM] Followup to: Help with Spectrophotometer Optics Alignment
In-Reply-To: <000a01c9c0e7$b74d13b0$25e73b10$@sleeter@roadrunner.com>
Message-ID: <Pine.LNX.4.44.0904201839400.25646-100000@uno.canit.se>

On Sun, 19 Apr 2009, David Sleeter wrote:

> In part of one of Dominic-Luc?s replies he said:
> ?The instruments I have seen have always had slightly larger gratings than
> beam width at the grating, but mirrors can be much larger than grating.
> Basic arrangement for monochromators I know of is:
>
> slit 1 > mirror 1 > grating > mirror 2 > slit 2?.
>
>
> When I read this, I realized that the instruments I have to realign use a
> unique single-beam, double-pass optical arrangement. They use three slits,
> and three mirrors in the following order:
>
> entrance slit > concave mirror 1 > grating > central slit > central flat
> mirror > back out the central slit > grating again > concave mirror 2 > exit
> slit.


Which component moves in order to select wavelength in this
arrangement? What is this instrument typically used for?

I am not convinced the extra slit is anything to do with
precision, at least of wavelength. The fluorescence spec in
my lab is accurate to about 1 nm using arrangement I described.
Others, these days, use diode arrays, no monochromators. I am
guessing your instrument is custom job or old.

Dominic


From vla at copper.net  Tue Apr 21 04:07:48 2009
From: vla at copper.net (vladimir sacek)
Date: Mon, 20 Apr 2009 15:07:48 -0400
Subject: [ATM] Higher Order Spherical Aberration in a Doublet
References: <49EA548D.9070304@rcn.com><000a01c9c084$86ff3ca0$504ff804@Handsome><49EA7A1A.5060406@rcn.com>
	<000601c9c0a8$cf685610$d05ff804@Handsome>
Message-ID: <000c01c9c1eb$4d0ca740$4b4df804@Handsome>

In order to make the second surface of a doublet achromat
less strongly curved than the following surface, so that they
can have contact around the edge, glass combination has
to be changed. Looking at how R2 and R3 are defined
in terms of R1:

R2=(q1+1)R1/(q1-1)   and
R3=(nF2-nC2)(q1+1)R1/(nF1-nC1)(q2-)

where n(...) are appropriate indici of refraction for the front (1)
and rear (2) lens, and "q" is the lens shape factor q=(R2+R1)/(R2-R1),
with 1 and 2 now referring to lens surfaces, this can be accomplished
either by increasing dispersion of the rear glass, or decreasing it in 
front.
As long as index remains nearly unchanged, the shape factors don't change
significantly, and spherical and coma will remain well corrected.

I replaced rear glass (F2) with TIF6, without recalculating for exact
shape factors (index differential is only ~0.003), merely relaxing the radii
in proportion to the needed f.l. for each element. After some minor
adjustments, resulting doublet (80mm f/5) has the second radius 6.5mm
longer than the third:

R1/t1,M1/R2:  310 / 12.5, BK7 / -240
interspace: 0.15mm, air
R3/t2.M2/R3: -233.5 / 6.25, TIF6  / -750

Due to less favorable partial dispersion differential, the secondary 
spectrum
is about 30% greater than the minimum possible. Since the nominal Abbe 
number
difference between F2 and TIF6 is 5.39 (36.4 and 31.21, respectively), 
resulting
in transforming radii differential (R2-R3) from -2.1mm to +6.5mm, it can be
assumed that Abbe differential needed for radii equalization is about 1.4 
here
(V~35 for the rear glass). Assuming similar less favorable partial 
dispersions,
secondary spectrum would be 7-8% above the minimum possible. It probably
can be nearly eliminated with a proper choice of glass.

Vla


----- Original Message ----- 
From: "vladimir sacek" <vla at copper.net>
To: <atm at atmlist.net>
Sent: Sunday, April 19, 2009 12:39 AM
Subject: Re: [ATM] Higher Order Spherical Aberration in a Doublet


> Richard Snashall wrote:
>
>> That does not eliminate the problem of needing a shim.
>> To not need the shim, the edge needs to be in contact,
>> not the center.
>>
>> Also I have a problem with it meeting the specifications.
>> It does not appear to be aplanatic in the green, nor does
>> it have canonical F-C correction.
>>
> No need for shim once the retainer ring brings the lenses together.
> It cannot be aplanatic, since it has non-zero higher-order coma. The
> one you posted is not aplanatic either, but it does have less coma.
> The one I posted has 0.075 wave RMS at ~2.8 degrees off
> axis; astigmatism there is 1.4 waves RMS,  making coma entirely
> invisible (it even has slightly lower total RMS error than your 
> "aplanat").
>
> Higher-order coma is minimized to 1/5 by balancing with 1.2 times of
> lower-order coma of opposite sign. An aplanatic objective would have
> to have higher-order coma near cancelled, in addition to the lower-order 
> form.
>
> Chromatic correction is pretty close: 0.468 vs. 0.450 wave RMS F/C
> average. Nominal secondary spectrum nearly equalizes if the rear lens
> thickness increases to 8mm (neither is quite at 1/2000 canonical 
> correction).
>
> Vla
>
>
>
>
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/ 


From rmay at nethere.com  Tue Apr 21 06:28:39 2009
From: rmay at nethere.com (Bob May)
Date: Mon, 20 Apr 2009 14:28:39 -0700
Subject: [ATM] my first mirror
References: <761172.47151.qm@web50008.mail.re2.yahoo.com>
Message-ID: <000601c9c1fe$f9f97920$8f78fea9@amd>

Take a wander about my website for a lot of the questions you
have.
Plate glass usually has a green tint when looked at from the side
although "water white" will be clear.
Generally, if you take and do a fringe test (take two pieces of
glass that are suspected to be flat and clean them well and place
them on top of each other and use a flourscent light source and
you shold get purple and green fringes between them) and if you
get the fringes (they will be faint) then you havea ceartin
amount of flat.
If the 12" has crud around the edges for about 3/8" or so, it is
definitely a porthole although those tend to be 3/4" thick.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Tue Apr 21 06:29:01 2009
From: rmay at nethere.com (Bob May)
Date: Mon, 20 Apr 2009 14:29:01 -0700
Subject: [ATM] OT - test message, please ignore
References: <49EBE22E.2090601@simoivanov.com>
Message-ID: <000901c9c1ff$06ad1f00$8f78fea9@amd>

You've been tested.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From tom_krajci at tularosa.net  Tue Apr 21 12:16:06 2009
From: tom_krajci at tularosa.net (Tom Krajci)
Date: Mon, 20 Apr 2009 21:16:06 -0600
Subject: [ATM] Heat rope suppliers
In-Reply-To: <mailman.132.1240093883.4352.atm@atmlist.net>
References: <mailman.132.1240093883.4352.atm@atmlist.net>
Message-ID: <49ED3A76.2090908@tularosa.net>

I've looked for heat rope at
www.sciplus.com
and
www.surpluscenter.com
but I can't find heat rope.

Got any leads on current suppliers?

Thanks in advance.

-- 
-------------------------------------------
Tom Krajci
Cloudcroft, New Mexico
http://picasaweb.google.com/tom.krajci

Center for Backyard Astrophysics (CBA)
http://cbastro.org/ CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
-------------------------------------------



From jamescrombie at jamescrombie.com  Tue Apr 21 12:34:54 2009
From: jamescrombie at jamescrombie.com (James P Crombie)
Date: Mon, 20 Apr 2009 23:34:54 -0400
Subject: [ATM] Heat rope suppliers
In-Reply-To: <49ED3A76.2090908@tularosa.net>
References: <mailman.132.1240093883.4352.atm@atmlist.net>
	<49ED3A76.2090908@tularosa.net>
Message-ID: <49ED3EDE.2020304@jamescrombie.com>

Tom Krajci wrote:
> I've looked for heat rope at
> www.sciplus.com
> and
> www.surpluscenter.com
> but I can't find heat rope.
>
> Got any leads on current suppliers?
>
> Thanks in advance.
>
Tom
  This is all new stuff

http://www.omega.com/search/esearch.asp?start=0&perPage=10&summary=yes&sort=rank&search=HEAT+TAPE&submit=Search&ori=heat+tape

From stainless_steel at suddenlink.net  Wed Apr 22 02:58:24 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Tue, 21 Apr 2009 12:58:24 -0500
Subject: [ATM] ATM: Re: Waste of bandwidth-
Message-ID: <31A486052DE84518910D9ECF7C87466A@R101>


Wonderful!!! Excellent!!!

DLZ-130

>This is a test of the ATM broadcasting system.  Had this been an actually 
>ATM emergency you would be instructed to get back to grinding.

>Anthony
_______________________________________________
>ATM mailing list http://www.atmlist.net/ 


From stainless_steel at suddenlink.net  Wed Apr 22 04:48:32 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Tue, 21 Apr 2009 14:48:32 -0500
Subject: [ATM] ATM: John Upton's treatment of my article-
Message-ID: <4C109BA2ED324A43ACA113B4D2899B6D@R101>


My Dear Good colleagues-

The other day, I suggested the various places that you can read 
"Understanding Foucault" for free, on the web. I mentioned Bob May's 
excellent treatment of it, on his site (everybody should have his URL 
memorized, by now- I think he puts it in each post and riposte)- and of 
course, the atmsite at www.atmsite.org - but I think I inadvertantly gave 
the wrong URL for John's page on the article. It seems someone has a web 
site with the same name, or a similar name, and I didn't check it out 
thoroughly enough.

I have not seen any posts by John Upton in a very long time, though I 
believe he is, or was, a member of our august forum. In any case, his 
website is very comprehensive and  interesting, as Bob's most certainly is, 
and so here is the URL for his formatting of "Understanding Foucault":

http://www.atm-workshop.com/foucault.html

So none of you need to buy the book; but for those who have, thank you. All 
of the extra articles that my agent put in there are available as either 
HTML illustrated emails, or attached Word documents, for FREE to any who 
requests them.

Mainly wanted to fix my previous error in reporting John's version of it 
erroneously (wrong URL).

As a very knowledgeable and experienced member of our list suggested (I 
believe all of you will remember):

"Grind more, worry less."

Well said.

DLZ-130

P.S.- And a thank you to Michael Lindner for his freely offered and 
published in the book, elementary, and very elegant, simple "Foucault 
Simulator" program. Thank you, Michael. Thank you all for your appreciation 
of "Understanding Foucault."  And thank you, Bob, for continuing to carry 
the article, and John, if he still is reading the posts.



From rmay at nethere.com  Wed Apr 22 05:44:00 2009
From: rmay at nethere.com (Bob May)
Date: Tue, 21 Apr 2009 13:44:00 -0700
Subject: [ATM] my first mirror
References: <761172.47151.qm@web50008.mail.re2.yahoo.com>
	<000601c9c1fe$f9f97920$8f78fea9@amd>
	<770328.98339.qm@web50006.mail.re2.yahoo.com>
Message-ID: <000701c9c2c1$e7d14ca0$8f78fea9@amd>

   You're in PANIC mode right now!!!  Settle down and realize
that it really is easy to make a mirror.
You said that the 6" has a code on it.  If that code is a 6 digit
number in the 40000-80000 range then it may be a glass type code
which means that it is optical glass rather than Pyrex.  There
may also be a letter(s) and number up to 99 for a code.
Something like KzFs-N23 for example of a long code string.   This
is a manufacturer's code for the glass.
As to which side to grind, always grind the larger side as you
are interested in aperture.  What is on the other side for a
mirror is irrrevelant as you're not looking through the glass.  I
would grind a really mountainy surface down a bit to make the
mounting easier but you haven't mentioned inch high mountians on
the glass.
As a final word for this post, don't think too much about the
process and try to find out why before you do something.  You do
it the way that all of the sites say to do it, it will come out
fine.  I've got one grinder in my grinding class right now that
is positively full of questions and my problem is to get him back
to grinding as he keeps getting afraid that he's doing something
wrong.  Just grind!
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Wed Apr 22 05:46:27 2009
From: rmay at nethere.com (Bob May)
Date: Tue, 21 Apr 2009 13:46:27 -0700
Subject: [ATM] Heat rope suppliers
References: <mailman.132.1240093883.4352.atm@atmlist.net>
	<49ED3A76.2090908@tularosa.net>
Message-ID: <001201c9c2c2$44a863a0$8f78fea9@amd>

It's an electrical/electronic part.  Places like Mouser and
Digikey are good first searches.
You can also make up your own with resistors soldered in series
and RTV'd into a string on the place where you want the heat.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Wed Apr 22 05:52:29 2009
From: rmay at nethere.com (Bob May)
Date: Tue, 21 Apr 2009 13:52:29 -0700
Subject: [ATM] ATM: John Upton's treatment of my article-
References: <4C109BA2ED324A43ACA113B4D2899B6D@R101>
Message-ID: <001501c9c2c3$1658cf20$8f78fea9@amd>

Being as to my website is at the Astronomy website where it
should stay until it gets obselete (yeah, right!) and at a free
website at Tonga (the reason for the .to extension on the
website) which will probably die someday when the server decides
to stop it, the website should live well beyond me.  John Huggins
knows how to gain access to the Astronomy website (he owns it) so
I know that it will be possible after I'm dead that he can extend
it if necessary and spread it into other sites if that is his
desires.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From thomas at moiler.com  Wed Apr 22 19:38:10 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Wed, 22 Apr 2009 20:38:10 +1000
Subject: [ATM] Update on my cast cellular mirror work.
Message-ID: <024e01c9c336$6ff94ff0$4febefd0$@com>

Hi All,

 

Ok so it's been nearly a year since I cast the first blank, and I finally
found the time to start working the blank. 

 

So here my observations on how things are progressing:

 

Size: diameter 419mm (16.5"), thickness 52mm (2").

Weight: as cast 7.5kgs (16.5lbs), with curve generated and ready to fine
grind: 6.2kgs (13.64lbs) which includes a plaster and plate glass plug in
the central perforation.

Present sag: 7.35mm (F/3.56)

 

At this point the face plate to the best of my measuring is of a very
uniform 12mm thickness and by the end of fine grinding should be ~11mm. This
will be confirmed with a "sonic" measuring device for window examination.
There is little or no strain present and all the surface divitrification has
been ground away. There are still some rather nasty striae present and these
will be there to the end. I expect the final weight to be ~6kgs (13.2lbs).

 

I will report further when fine grinding is complete and flash polish has
been attained to see if print through is going to be a major problem. 

 

Cheers, Thomas Janstrom.

Little Gems.

 <http://tjlittlegems.com/index.htm> http://tjlittlegems.com 

 


From rflrs at verizon.net  Thu Apr 23 00:13:23 2009
From: rflrs at verizon.net (Richard Snashall)
Date: Wed, 22 Apr 2009 11:13:23 -0400
Subject: [ATM] [Fwd: Re: Higher Order Spherical Aberration in a Doublet]
In-Reply-To: <49EF2F57.1010107@rcn.com>
References: <49EF2F57.1010107@rcn.com>
Message-ID: <49EF3413.5090009@verizon.net>

vladimir sacek wrote:
>
> Richard F.L.R. Snashall wrote:
>>
>> Does anyone know of such an all-spherical achromat
>> that does not require the shims -- i.e. a contact
>> doublet that nulls the zonal error?
>>
> If the goal is to eliminate air space, this would do:
>
> (80mm f/6.25 contact doublet with zero separation)
>
> R1/t1,M1/R2:  303.8 / 12.5, BK7 / -180.4
> R3/t2.M2/R3: -182.5 / 6.25, F2  / -737.5
On your refractor design web page, you describe LSA,
HSA, and LHSA.  At f/6.25, residual LSA can affect
these doublets.  I attempted to get LHSA without the
need for figuring.  To do that, I needed to pick the
right glasses.

I believe it would be less difficult if the edges
were in contact.  I was not able to come up with a
reasonable solution.  Early attempts with variable
model glasses seems to indicate that this is going
the same way as a Littrow doublet with nulled LSA
and coma -- very high indices of refraction.  Even
then, the internal surfaces appear to get quite steep,
so that even the LHSA residual is larger than the LSA
I was attempting to get rid of in the first place.



From rmay at nethere.com  Thu Apr 23 06:26:37 2009
From: rmay at nethere.com (Bob May)
Date: Wed, 22 Apr 2009 14:26:37 -0700
Subject: [ATM] my first mirror
References: <761172.47151.qm@web50008.mail.re2.yahoo.com>
	<000601c9c1fe$f9f97920$8f78fea9@amd>
	<770328.98339.qm@web50006.mail.re2.yahoo.com>
	<000701c9c2c1$e7d14ca0$8f78fea9@amd>
	<590361.11658.qm@web50005.mail.re2.yahoo.com>
Message-ID: <000d01c9c391$28010700$8f78fea9@amd>

Well, the number isn't a 6 digit optical glass code so it is
probably a product code or lot code for whatevrer the glass was
made for.
An optical flat is generally considered to be a piece of glass
which has a surface with an error of flatness of less than 1/4
wave.  This kind of depends upon its usage.  You can buy optical
flats with surface accuracys of up to 1/20th of a wave from
stock.
No, you don't need to make a "flat" first. You just start
grinding the way that has been described and you will quickly get
the proper concave surface you desire.
As to how to grind the glass, go to my website and read the
extensive article on grinding a mirror.  A lot of the questions
that you have asked are already answered (and a lot more!) in the
article including how to actually grind.  If you want a one stop
source for grinding supplies, go to the Gotgrit website and order
a kit.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Thu Apr 23 06:30:23 2009
From: rmay at nethere.com (Bob May)
Date: Wed, 22 Apr 2009 14:30:23 -0700
Subject: [ATM] Update on my cast cellular mirror work.
References: <024e01c9c336$6ff94ff0$4febefd0$@com>
Message-ID: <000e01c9c391$8ddb3f00$8f78fea9@amd>

If the face plate is 1/2" (12mm), you shouldn't have any
printthrough problems unless the supports are few and far
between.
>From the fine grinding stage to the polishing and figuring, you
don't want to do any real pressure on the surface as this will
push the support area more than other areas.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From vla at copper.net  Thu Apr 23 09:59:54 2009
From: vla at copper.net (vladimir sacek)
Date: Wed, 22 Apr 2009 20:59:54 -0400
Subject: [ATM] [Fwd: Re: Higher Order Spherical Aberration in a Doublet]
References: <49EF2F57.1010107@rcn.com> <49EF3413.5090009@verizon.net>
Message-ID: <001d01c9c3ae$d1eb14a0$8c5cf804@Handsome>


Richard Snashall wrote:

> I believe it would be less difficult if the edges
> were in contact.  I was not able to come up with a
> reasonable solution.  Early attempts with variable
> model glasses seems to indicate that this is going
> the same way as a Littrow doublet with nulled LSA
> and coma -- very high indices of refraction.  Even
> then, the internal surfaces appear to get quite steep,
> so that even the LHSA residual is larger than the LSA
> I was attempting to get rid of in the first place.
> 
Just looking at the glass diagram (Schott), there don't 
seem to be good options using either BK7 or F2, or alike.
It would require more involved search for those right glasses,
if there are such. The question is if it's worth it. The combined
higher order spherical is already negligibly low. As for 
eliminating the spacing, it obviously has the convenience
of easier mounting and lowered sensitivity to misalignment.
On the other hand, it imposes tighter tolerances on lens 
fabrication; there is no possibility to compensate for smaller
deviations by adjusting lens separation (or it can be done only 
one way, by creating lens separation, which is against the 
purpose of designing effort). 

The good part is that following this I've found and fixed another
couple of errors on my site. I can see now I'll be doing it
till the end of time.

Vla

From rflrs at verizon.net  Thu Apr 23 10:44:42 2009
From: rflrs at verizon.net (Richard F.L.R. Snashall)
Date: Wed, 22 Apr 2009 21:44:42 -0400
Subject: [ATM] Site Moved
Message-ID: <49EFC80A.5010207@verizon.net>

If I haven't quite yet entered the 21st century, I
at least entered the 20th with an upgrade of my ISP.
If anybody needs it, my site has been moved to:

   http://mysite.verizon.net/rflrs

Other than that, all else should be the same.



From tom_krajci at tularosa.net  Thu Apr 23 11:17:19 2009
From: tom_krajci at tularosa.net (Tom Krajci)
Date: Wed, 22 Apr 2009 20:17:19 -0600
Subject: [ATM] Heat rope suppliers
In-Reply-To: <mailman.58.1240448416.10065.atm@atmlist.net>
References: <mailman.58.1240448416.10065.atm@atmlist.net>
Message-ID: <49EFCFAF.5070406@tularosa.net>

>From: "Bob May" <rmay at nethere.com>

>It's an electrical/electronic part.  Places like Mouser and
>Digikey are good first searches.

Negative on both.  Lots of soldering heaters, but no heat rope or heat tape that I could find.

I used to find lots of places that carried that stuff...not these days.

>You can also make up your own with resistors soldered in series
>and RTV'd into a string on the place where you want the heat.

That's the last resort, but I'd prefer to find tape/rope.

-- 
-------------------------------------------
Tom Krajci
Cloudcroft, New Mexico
http://picasaweb.google.com/tom.krajci

Center for Backyard Astrophysics (CBA)
http://cbastro.org/ CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
-------------------------------------------



From hermit at outofoptions.org  Thu Apr 23 11:23:54 2009
From: hermit at outofoptions.org (hermit)
Date: Wed, 22 Apr 2009 22:23:54 -0400
Subject: [ATM] Heat rope suppliers
In-Reply-To: <49EFCFAF.5070406@tularosa.net>
References: <mailman.58.1240448416.10065.atm@atmlist.net>
	<49EFCFAF.5070406@tularosa.net>
Message-ID: <49EFD13A.3090707@outofoptions.org>

I just googled, and failed, but appliance parts stores used to carry 
braided drain heaters.  They were rated at 120 volts, various wattages.  
Gemline used to be a supplier.  Not sure if they are still in business 
though.

Ken Lowther

Tom Krajci wrote:
>> From: "Bob May" <rmay at nethere.com>
>
>> It's an electrical/electronic part.  Places like Mouser and
>> Digikey are good first searches.
>
> Negative on both.  Lots of soldering heaters, but no heat rope or heat 
> tape that I could find.
>
> I used to find lots of places that carried that stuff...not these days.
>
>> You can also make up your own with resistors soldered in series
>> and RTV'd into a string on the place where you want the heat.
>
> That's the last resort, but I'd prefer to find tape/rope.
>


From broward32666 at yahoo.com  Thu Apr 23 11:27:26 2009
From: broward32666 at yahoo.com (Charles Broward)
Date: Wed, 22 Apr 2009 19:27:26 -0700 (PDT)
Subject: [ATM] Heat rope suppliers
In-Reply-To: <49EFCFAF.5070406@tularosa.net>
References: <mailman.58.1240448416.10065.atm@atmlist.net>
	<49EFCFAF.5070406@tularosa.net>
Message-ID: <793899.55380.qm@web110813.mail.gq1.yahoo.com>

Hi, Go to www.mcmaster.com and search for heat rope or heat tape....lots there.

Clear sky
Chuck

 C.S.Broward
GhastlySky Observatory
Gainesville, Florida


WWW.Floridastars.org
ATM Coord, Alcor




________________________________
From: Tom Krajci <tom_krajci at tularosa.net>
To: atm at atmlist.net
Sent: Wednesday, April 22, 2009 10:17:19 PM
Subject: Re: [ATM] Heat rope suppliers

>From: "Bob May" <rmay at nethere.com>

>It's an electrical/electronic part.  Places like Mouser and
>Digikey are good first searches.

Negative on both.  Lots of soldering heaters, but no heat rope or heat tape that I could find.

I used to find lots of places that carried that stuff...not these days.

>You can also make up your own with resistors soldered in series
>and RTV'd into a string on the place where you want the heat.

That's the last resort, but I'd prefer to find tape/rope.

-- 
-------------------------------------------
Tom Krajci
Cloudcroft, New Mexico
http://picasaweb.google.com/tom.krajci

Center for Backyard Astrophysics (CBA)
http://cbastro.org/ CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
-------------------------------------------


_______________________________________________
ATM mailing list http://www.atmlist.net/



      

From hermit at outofoptions.org  Thu Apr 23 11:34:57 2009
From: hermit at outofoptions.org (hermit)
Date: Wed, 22 Apr 2009 22:34:57 -0400
Subject: [ATM] Heat rope suppliers
In-Reply-To: <49EFD13A.3090707@outofoptions.org>
References: <mailman.58.1240448416.10065.atm@atmlist.net>	<49EFCFAF.5070406@tularosa.net>
	<49EFD13A.3090707@outofoptions.org>
Message-ID: <49EFD3D1.5050503@outofoptions.org>

I should have asked, how long do you want it to be or what are you using 
it for.  Their are other places in refrigerators that use heaters also, 
like mullion strips and ice maker fill lines.

Ken Lowther

hermit wrote:
> I just googled, and failed, but appliance parts stores used to carry 
> braided drain heaters.  They were rated at 120 volts, various 
> wattages.  Gemline used to be a supplier.  Not sure if they are still 
> in business though.
>
> Ken Lowther
>
> Tom Krajci wrote:
>>> From: "Bob May" <rmay at nethere.com>
>>
>>> It's an electrical/electronic part.  Places like Mouser and
>>> Digikey are good first searches.
>>
>> Negative on both.  Lots of soldering heaters, but no heat rope or 
>> heat tape that I could find.
>>
>> I used to find lots of places that carried that stuff...not these days.
>>
>>> You can also make up your own with resistors soldered in series
>>> and RTV'd into a string on the place where you want the heat.
>>
>> That's the last resort, but I'd prefer to find tape/rope.
>>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


From djd521 at verizon.net  Thu Apr 23 11:46:44 2009
From: djd521 at verizon.net (Don D'Egidio)
Date: Wed, 22 Apr 2009 22:46:44 -0400
Subject: [ATM] Heat rope suppliers
References: <mailman.58.1240448416.10065.atm@atmlist.net>
	<49EFCFAF.5070406@tularosa.net>
Message-ID: <D126935EA625403FBC39B7BCB520F72A@donaldp4>

Tom,

Any plumbing supplier should carry heat rope.

Don

----- Original Message ----- 
From: "Tom Krajci" <tom_krajci at tularosa.net>
To: <atm at atmlist.net>
Sent: Wednesday, April 22, 2009 10:17 PM
Subject: Re: [ATM] Heat rope suppliers


> >From: "Bob May" <rmay at nethere.com>
>
>>It's an electrical/electronic part.  Places like Mouser and
>>Digikey are good first searches.
>
> Negative on both.  Lots of soldering heaters, but no heat rope or heat tape that I could find.
>
> I used to find lots of places that carried that stuff...not these days.
>
>>You can also make up your own with resistors soldered in series
>>and RTV'd into a string on the place where you want the heat.
>
> That's the last resort, but I'd prefer to find tape/rope.
>
> -- 
> -------------------------------------------
> Tom Krajci
> Cloudcroft, New Mexico
> http://picasaweb.google.com/tom.krajci
>
> Center for Backyard Astrophysics (CBA)
> http://cbastro.org/ CBA New Mexico
>
> American Association of Variable Star
> Observers (AAVSO): KTC http://www.aavso.org/
> -------------------------------------------
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/ 



From dlwebb at canit.se  Thu Apr 23 15:20:20 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Thu, 23 Apr 2009 08:20:20 +0200 (MET DST)
Subject: [ATM] Site Moved
In-Reply-To: <49EFC80A.5010207@verizon.net>
Message-ID: <Pine.LNX.4.44.0904230818280.12386-100000@uno.canit.se>

On Wed, 22 Apr 2009, Richard F.L.R. Snashall wrote:

> If I haven't quite yet entered the 21st century, I
> at least entered the 20th with an upgrade of my ISP.
> If anybody needs it, my site has been moved to:
>
>    http://mysite.verizon.net/rflrs
>
> Other than that, all else should be the same.

Very nice! Direct and to the point! I'll post something in a
second about your Cass secondary test, assigning a specific
subject line.

Dominic


From dlwebb at canit.se  Thu Apr 23 15:49:43 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Thu, 23 Apr 2009 08:49:43 +0200 (MET DST)
Subject: [ATM] RFLR Snashall's Cass secondary test
In-Reply-To: <49EFC80A.5010207@verizon.net>
Message-ID: <Pine.LNX.4.44.0904230820260.12386-100000@uno.canit.se>


On Wed, 22 Apr 2009, Richard F.L.R. Snashall wrote:

> If anybody needs it, my site has been moved to:
>
>    http://mysite.verizon.net/rflrs

Again, nice job on your website. Your proposed Cass test:

http://mysite.verizon.net/rflrs/sectest.htm

requires some extra lenses, at least some of which must
need to be custom made. Is it not easier to just test
the completed system? Presumably the primary can be tested
thoroughly and the secondary ROC can be measured from the
back side. Alternatively, the ROC of the concave tool
could easily be measured, which should just be reverse
sign of ROC of mirror. Departure from predicted system
performance then originates from defects in the secondary
figure.

For instance, with a Ronchi grating and light source at
system focus and examined from some (great) distance in
front of scope? This has been done on other systems,
like Schmidt cameras. If I remember this test correctly,
system with good figure projects straight lines.

Dominic


From vladimir.galogaza1 at zg.t-com.hr  Thu Apr 23 18:02:05 2009
From: vladimir.galogaza1 at zg.t-com.hr (Vladimir Galogaza)
Date: Thu, 23 Apr 2009 11:02:05 +0200
Subject: [ATM] Heat rope suppliers
References: <mailman.58.1240448416.10065.atm@atmlist.net>
	<49EFCFAF.5070406@tularosa.net>
Message-ID: <943C9184F85F48C6AE5F3D8BF2C9232B@piv555a133b59e>

Hi Tom,

Try this

http://www.heatingtapes.com/


Regards
Vladimir.


From wkitty42 at windstream.net  Fri Apr 24 01:09:32 2009
From: wkitty42 at windstream.net (waldo kitty)
Date: Thu, 23 Apr 2009 12:09:32 -0400
Subject: [ATM] Heat rope suppliers
In-Reply-To: <49EFCFAF.5070406@tularosa.net>
References: <mailman.58.1240448416.10065.atm@atmlist.net>
	<49EFCFAF.5070406@tularosa.net>
Message-ID: <49F092BC.3010605@windstream.net>

Tom Krajci wrote:
>> From: "Bob May" <rmay at nethere.com>
> 
>> It's an electrical/electronic part.  Places like Mouser and
>> Digikey are good first searches.
> 
> Negative on both.  Lots of soldering heaters, but no heat rope or heat 
> tape that I could find.
> 
> I used to find lots of places that carried that stuff...not these days.
> 
>> You can also make up your own with resistors soldered in series
>> and RTV'd into a string on the place where you want the heat.
> 
> That's the last resort, but I'd prefer to find tape/rope.
> 

i don't know how long a section yo uare looking for but you should be able to 
find it at home/builder supply stores like lowes or home depot or possible even 
a plumbing place... i'm thinking of the electrical heating item that you can 
wind around water pipes to keep them from freezing in the winter or to thaw them 
if they do freeze (but thawing takes a while)...

-- 
NOTE: NEW EMAIL ADDRESS!!

        _\/
       (@@)                      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 jack.swaton at starryhost.com  Fri Apr 24 01:16:53 2009
From: jack.swaton at starryhost.com (Jack Swaton @ Starry Host)
Date: Thu, 23 Apr 2009 09:16:53 -0700
Subject: [ATM] Heat rope suppliers
In-Reply-To: <49F092BC.3010605@windstream.net>
References: <mailman.58.1240448416.10065.atm@atmlist.net><49EFCFAF.5070406@tularosa.net>
	<49F092BC.3010605@windstream.net>
Message-ID: <743F53F011D3405B85596454FF34FF0D@MRBNOTEBOOK>

I've seen several sites that dismember old electric blankets to pull the
heat wires and controller from them.

Jack Swaton
www.StarryHost.com


From jbentz at inreach.com  Fri Apr 24 04:08:25 2009
From: jbentz at inreach.com (Jan Bentz)
Date: Thu, 23 Apr 2009 12:08:25 -0700
Subject: [ATM] RFLR Snashall's Cass secondary test
In-Reply-To: <Pine.LNX.4.44.0904230820260.12386-100000@uno.canit.se>
References: <Pine.LNX.4.44.0904230820260.12386-100000@uno.canit.se>
Message-ID: <49F0BCA9.2090900@inreach.com>

Dominic-Luc Webb wrote:

>On Wed, 22 Apr 2009, Richard F.L.R. Snashall wrote:
>
>  
>
>>If anybody needs it, my site has been moved to:
>>
>>   http://mysite.verizon.net/rflrs
>>    
>>
>
>Again, nice job on your website. Your proposed Cass test:
>
>http://mysite.verizon.net/rflrs/sectest.htm
>
>requires some extra lenses, at least some of which must
>need to be custom made. Is it not easier to just test
>the completed system? Presumably the primary can be tested
>thoroughly and the secondary ROC can be measured from the
>back side. Alternatively, the ROC of the concave tool
>could easily be measured, which should just be reverse
>sign of ROC of mirror. Departure from predicted system
>performance then originates from defects in the secondary
>figure.
>
>For instance, with a Ronchi grating and light source at
>system focus and examined from some (great) distance in
>front of scope? This has been done on other systems,
>like Schmidt cameras. If I remember this test correctly,
>system with good figure projects straight lines.
>
>Dominic
>
>_______________________________________________
>ATM mailing list http://www.atmlist.net/
>
>  
>
Dominic -- You remember correctly about the Schmidt test.  But you must 
realize that this test while sensitive enough for a short focal length 
photographic system is unlikely to be sensitive enough in practice for a 
long focal length diffraction ltd. visual system.  It should get you in 
the ballpark if you can get far enough away (20 or 30 focal lengths at 
least) and can deal with the turbulance.  Perhaps a small telescope with 
a grid reticle?

Jan Bentz

From djd521 at verizon.net  Fri Apr 24 04:28:21 2009
From: djd521 at verizon.net (Don D'Egidio)
Date: Thu, 23 Apr 2009 15:28:21 -0400
Subject: [ATM] ATMOS 8.0
Message-ID: <5117E587E7C34E52AD2368E3F4D4609C@donaldp4>

Is there a manual online anyplace or a tutorial for using the program? I have been to Massimo's 
website. A friend lent me his DVD to see if I can learn the program and then teach him. I have no 
previous ray tracing experience. Are there any .atm files for a C11 SCT?

Thanks,
Don 



From stainless_steel at suddenlink.net  Fri Apr 24 04:41:35 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Thu, 23 Apr 2009 14:41:35 -0500
Subject: [ATM] ATM: Re: RFLR's Cass. Secondary test
Message-ID: <3BECBB934805483DA870301EB56CE260@R101>

Yes, Jan, Dominic-

This is a null test, and is a fool proof set up for a Cass secondary for 
figuring. One could use a flat like Ritchey did, facing the system (it can 
even be a subdiamter flat, reaching only from the edge of the secondary to 
the edge of the primary)- in this, Perkin Elmer lied to the nation when they 
said they needed a full diameter flat for an autocollimation test for the 
Hubble space telescope. Bumblers, liars.).

Have the tube, and the mounting hardware finished, and take it to a location 
where you can find a light that is small, and very distant (failing that, 
have the mount finished and use a 1st or 2nd magnitude star) and do a simple 
null test- then, to paraphrase our own American Genius Gee Dubbya Ritchy, 
all one need do is "soften down the .707 zone on the secondary." He makes 
figuring a secondary sound like child's play.

For what it's worth-

DLZ-130



>>For instance, with a Ronchi grating and light source at
>>system focus and examined from some (great) distance in
>>front of scope? This has been done on other systems,
>>like Schmidt cameras. If I remember this test correctly,
>>system with good figure projects straight lines.
>>
>>Dominic
>>


From rmay at nethere.com  Fri Apr 24 05:38:20 2009
From: rmay at nethere.com (Bob May)
Date: Thu, 23 Apr 2009 13:38:20 -0700
Subject: [ATM] Heat rope suppliers
References: <mailman.58.1240448416.10065.atm@atmlist.net>
	<49EFCFAF.5070406@tularosa.net>
Message-ID: <000c01c9c453$727b9080$8f78fea9@amd>

How about Grainger?  Sorry but I haven't bothered to look in any
of the catalogs - don't have them at home.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From burrjaw at earthlink.net  Fri Apr 24 08:24:05 2009
From: burrjaw at earthlink.net (Jim Burrows)
Date: Thu, 23 Apr 2009 16:24:05 -0700
Subject: [ATM] ATM: Re: RFLR's Cass. Secondary test
In-Reply-To: <3BECBB934805483DA870301EB56CE260@R101>
References: <3BECBB934805483DA870301EB56CE260@R101>
Message-ID: <E1Lx8Jl-0000of-Fa@elasmtp-kukur.atl.sa.earthlink.net>

At 2009-04-23 14:41 -0500, DLS-130.net wrote:

>This is a null test, and is a fool proof set up for a Cass secondary 
>for figuring. One could use a flat like Ritchey did, facing the 
>system (it can even be a subdiamter flat, reaching only from the 
>edge of the secondary to the edge of the primary)- in this, Perkin 
>Elmer lied to the nation when they said they needed a full diameter 
>flat for an autocollimation test for the Hubble space telescope. 
>Bumblers, liars.).

I'm in favor of the good ol' tried and true Hindle test.  Ya gotta 
make a sufficiently large spherical mirror, but that's not too hard - 
been there, done that.  The really nice part is the test can be run 
non-null - Foucault test data can be processed to tell you what, and 
how big the deviations are on the secondary.

I've got an elaborate program to run 2D Hartmann on the Hindle setup.

And if anyone could use it, I'm willing to loan my 10" f/1 Hindle 
sphere, presently being used as an excellent shaving mirror <g>.

         -- Jim Burrows
         -- http://home.earthlink.net/~burrjaw
         -- mailto:burrjaw at earthlink.net
         -- Seattle N47.4723 W122.3662 (WGS84)


From rflrs at verizon.net  Fri Apr 24 10:28:44 2009
From: rflrs at verizon.net (Richard F.L.R. Snashall)
Date: Thu, 23 Apr 2009 21:28:44 -0400
Subject: [ATM] RFLR Snashall's Cass secondary test
In-Reply-To: <Pine.LNX.4.44.0904230820260.12386-100000@uno.canit.se>
References: <Pine.LNX.4.44.0904230820260.12386-100000@uno.canit.se>
Message-ID: <49F115CC.7060305@verizon.net>

Dominic-Luc Webb wrote:
>
> Again, nice job on your website. Your proposed Cass test:
>
> http://mysite.verizon.net/rflrs/sectest.htm
>
> requires some extra lenses, at least some of which must
> need to be custom made. Is it not easier to just test
> the completed system? Presumably the primary can be tested
> thoroughly and the secondary ROC can be measured from the
> back side. Alternatively, the ROC of the concave tool
> could easily be measured, which should just be reverse
> sign of ROC of mirror. Departure from predicted system
> performance then originates from defects in the secondary
> figure.
Actually, I was looking for a way to cheaply test convex
lens surfaces.


From dlwebb at canit.se  Fri Apr 24 18:28:37 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Fri, 24 Apr 2009 11:28:37 +0200 (MET DST)
Subject: [ATM] ATM: Re: RFLR's Cass. Secondary test
In-Reply-To: <E1Lx8Jl-0000of-Fa@elasmtp-kukur.atl.sa.earthlink.net>
Message-ID: <Pine.LNX.4.44.0904241100530.10533-100000@uno.canit.se>


On Thu, 23 Apr 2009, Jim Burrows wrote:

> At 2009-04-23 14:41 -0500, DLS-130.net wrote:
>
> >This is a null test, and is a fool proof set up for a Cass secondary
> >for figuring.

This is apparently refering to the test I brought up using a
Ronchi grating at focus and standing many focal lengths in
front of scope. I too have wondered how practical this is
for a very long focal length system. Presumably one must
stand many system (i.e., effective focal lengths) in front
of scope ( >20 perhaps???). The Cass configs I have tinkered
with have effective focal lengths around 5 meters. Atmospheric
turbulence won't be terribly cooperative above this, so
regardless of system aperture, I can't imagine many people will
make more than 10 meter effective focal length Cass systems.
Standing 20 EFL's in front of this is 200 meters. Admittedly,
doing this test on a paved highway on a very hot day won't
work well. But I would guess it really should work in the
early evening in a grass field if raised well above the ground.

Another test, of which I have not heard so much discussion here
is to image a target placed a great distance in front of
the completed system. Edmund Scientific sells a number of
targets and I have dreamed up some of my own. Defects in
such targets imaged at the system focus without eyepiece
should be diagnostic, assuming one can simulate the image
to derive residual defects requiring further figuring.


> I'm in favor of the good ol' tried and true Hindle test.  Ya gotta
> make a sufficiently large spherical mirror, but that's not too hard -
> been there, done that.
> I've got an elaborate program to run 2D Hartmann on the Hindle setup.
>
> And if anyone could use it, I'm willing to loan my 10" f/1 Hindle
> sphere, presently being used as an excellent shaving mirror <g>.
>
>          -- Jim Burrows

Yes, and anyone making a Cass from scratch has a sphere (the
primary before parabolizing), albeit, not usually F/1. That
being said, I successfully made a 180 mm (7") diameter F/1
sphere from some old plate glass. Glass was not slumped,
roughly 19 mm thick. I used #40 or #60 SiC to generate the
curve. It was actually a lot easier and faster than I
expected.

Not being real familiar with the Hindle test and its permutations,
I wonder what diameter and F/ratio would be suggested for a
Hindle sphere to test the secondary for that Mak Club Mak-Cass
system I am working. Original design uses secondary of 73 mm
diameter with conic -2.32014)?

http://www.canit.se/~dlwebb/catadioptric/280maksutov/280maksutov.html

Original design will be modified, but only slightly, following
much advice from several people in this list.

Dominic


From rmay at nethere.com  Sat Apr 25 04:48:24 2009
From: rmay at nethere.com (Bob May)
Date: Fri, 24 Apr 2009 12:48:24 -0700
Subject: [ATM] RFLR Snashall's Cass secondary test
References: <Pine.LNX.4.44.0904230820260.12386-100000@uno.canit.se>
	<49F115CC.7060305@verizon.net>
Message-ID: <000c01c9c518$baef4620$8f78fea9@amd>

Richard, there are several different ways to check convex
surfaces.
For doing spheres (as in lenses where most of the surfaces are
desired to be spheres) the easiest way is to do a test plate,
just another piece of glass that has the convex version of the
curvature on it.  The simple fringe test (usually used for flats)
is how you test the surface for the desired curvature.
For hyperbolas, the Hindle test is not to expensive for smaller
(cass secondaries) convex surfaces and the Hindle sphere wants to
be about twice the curvature as the primary of the scope.
For surfaces other than this, the ray tracing and looking through
the glass at the far surface (which is then concave) works.  The
intent of the ray tracing is to find the apparent ROC of the zone
that is being tested so you can do the Foucault test on the
surface.  This means doing annular rings of varying size
according to the zones of the Couder Mask  and finding the ROC of
the zone.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rmay at nethere.com  Sat Apr 25 05:06:58 2009
From: rmay at nethere.com (Bob May)
Date: Fri, 24 Apr 2009 13:06:58 -0700
Subject: [ATM] ATM: Re: RFLR's Cass. Secondary test
References: <Pine.LNX.4.44.0904241100530.10533-100000@uno.canit.se>
Message-ID: <000e01c9c518$c95ef3e0$8f78fea9@amd>

General rule of thumb for the HIndle test that I've seen is that
the Hindle sphere wants to be about the same diameter as the
primary of the cass and about twice the curvature (half of the
ROC).  It is a fairly easy surface to do as it is spherical and
thus hard pitch will work well in polishing it up.  Longer ROC
and the size grows that is needed for the sphere.
Light path on the Hindle test is from a point source to the
secondary, then to the sphere and directly back to the secondary
and finally back to the destination.  A beamsplitter is probably
best used for the head on this as you want to have a coaxial beam
rather than something that has an offset in one direction.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From rflrs at verizon.net  Sat Apr 25 07:57:03 2009
From: rflrs at verizon.net (Richard F.L.R. Snashall)
Date: Fri, 24 Apr 2009 18:57:03 -0400
Subject: [ATM] RFLR Snashall's Cass secondary test
In-Reply-To: <000c01c9c518$baef4620$8f78fea9@amd>
References: <Pine.LNX.4.44.0904230820260.12386-100000@uno.canit.se>
	<49F115CC.7060305@verizon.net> <000c01c9c518$baef4620$8f78fea9@amd>
Message-ID: <49F243BF.7080406@verizon.net>

Bob May wrote:
> Richard, there are several different ways to check convex
> surfaces.
> For doing spheres (as in lenses where most of the surfaces are
> desired to be spheres) the easiest way is to do a test plate,
> just another piece of glass that has the convex version of the
> curvature on it.  The simple fringe test (usually used for flats)
> is how you test the surface for the desired curvature.
The same auxillary lens can be used for different
convex radii -- it just needs to focus light from
the RoC of the convex lens surface at a convenient
Foucault distance.




From donald_clement at yahoo.com  Sat Apr 25 08:11:53 2009
From: donald_clement at yahoo.com (don clement)
Date: Fri, 24 Apr 2009 16:11:53 -0700 (PDT)
Subject: [ATM] Heat rope suppliers
Message-ID: <930483.85516.qm@web34208.mail.mud.yahoo.com>


One could go to Omega.com or McMasterCarr as has been mentioned. You could roll your own using say an arrangement of resistors or make your own resistive paint from graphite or similar. Or just buy some nichrome, constantan thermocouple wire or similar resistive wire form Omega. Zinc oxide in RTV makes a good heat conductive but electrically resistive coating. 

bit of resistor trivia: http://www.uoguelph.ca/~antoon/gadgets/resistors/resistor.htm 

> Tom Krajci wrote:
> > I've looked for heat rope at
> > www.sciplus.com
> > and
> > www.surpluscenter.com
> > but I can't find heat rope.
> >
> > Got any leads on current suppliers?
> >
> > Thanks in advance.
> >



      

From thomas at moiler.com  Sat Apr 25 17:22:41 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Sat, 25 Apr 2009 18:22:41 +1000
Subject: [ATM] Some pictures of my progress on my crrnt project.
Message-ID: <025d01c9c57f$0260b320$07221960$@com>

For those not following my current adventures in mirror grinding, here's a
brief synopsis..

 

Mirror diameter: 419mm or 16.5".

F/4.03

Weight: ~6.2kgs

Current stage: Polishing, about 3-4hrs short (at the long end) of figuring.

Targeted completion date: 30th April (If I fail at that it won't get
finished for a further three months as I'm going on holidays the following
week to the US!)

 

http://www.pbase.com/praxis178/hobbies pictures of the project

 

http://www.pbase.com/image/111728845 something only an ATM* would find
funny..

 

Enjoy, comments etc. always welcome.

 

Cheers, Thomas Janstrom.

Little Gems.

 <http://tjlittlegems.com/index.htm> http://tjlittlegems.com 

 

.         ATM = "Amateur Telescope Maker" for those not in the know.


From rflrs at verizon.net  Sun Apr 26 00:49:14 2009
From: rflrs at verizon.net (Richard F.L.R. Snashall)
Date: Sat, 25 Apr 2009 11:49:14 -0400
Subject: [ATM] [Fwd: Re: Higher Order Spherical Aberration in a Doublet]
In-Reply-To: <001d01c9c3ae$d1eb14a0$8c5cf804@Handsome>
References: <49EF2F57.1010107@rcn.com> <49EF3413.5090009@verizon.net>
	<001d01c9c3ae$d1eb14a0$8c5cf804@Handsome>
Message-ID: <49F330FA.7030901@verizon.net>

vladimir sacek wrote:
>
> As for eliminating the spacing, it obviously has the convenience
> of easier mounting and lowered sensitivity to misalignment.
> On the other hand, it imposes tighter tolerances on lens fabrication; 
> there is no possibility to compensate for smaller
> deviations by adjusting lens separation (or it can be done only one 
> way, by creating lens separation, which is against the purpose of 
> designing effort).
Indeed.  I think that might be demonstrated with:

Title: dbl04-53x
80 mm f/6.25 Doublet

Surf    Radius   Thickness    Glass  Diameter

 STO  Infinity   -2.580798                 80
   2   311.272       12.65   N-BAK2        84
   3 -155.2465 0.001457944                 84
   4 -157.2018        5.18   S-TIM3        84
   5 -884.9417    490.7449                 84
 IMA   -188.44                           17.5

Here, the edge separation is 0.0030" (0.0762 mm), while
the center barely misses.  The difference in inner
surface sagittas is then [roughly] only that 0.0030".



From jaleblan at dakotacom.net  Sun Apr 26 01:11:27 2009
From: jaleblan at dakotacom.net (Jay LeBlanc)
Date: Sat, 25 Apr 2009 09:11:27 -0700
Subject: [ATM] ATM: Re: RFLR's Cass. Secondary test
In-Reply-To: <E1LxVmC-0004DG-FW@elasmtp-curtail.atl.sa.earthlink.net>
References: <3BECBB934805483DA870301EB56CE260@R101>
	<E1Lx8Jl-0000of-Fa@elasmtp-kukur.atl.sa.earthlink.net>
	<49F0FD99.2000206@dakotacom.net>
	<E1LxVmC-0004DG-FW@elasmtp-curtail.atl.sa.earthlink.net>
Message-ID: <49F3362F.4080606@dakotacom.net>

Thanks Jim and Bob for the info on the Hindle test!
-Jay-

From thomas at moiler.com  Sun Apr 26 21:47:15 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Sun, 26 Apr 2009 22:47:15 +1000
Subject: [ATM] warning: Massive cross posting,
	slightly OT: My impending visit to the USA.
Message-ID: <027801c9c66d$23443fa0$69ccbee0$@com>

Hi everyone,

 

Just a note to let everyone know that I'll be visiting the USA for three
months (quite a few of you already know this), this message is just to let
everyone else know some of the basic in case anyone else wants to catch up
with me at some point.

 

I'll be arriving in country on the 6th of May, and for May my time is mostly
my own, I'll be doing a course of studies at a school in Florida for all of
June, and then July is again mine to squander as I see fit. So if you're in
the South East of the US, and want to catch up, drop me a line and we can
see about working out the details.

 

I'd really like to put some faces to all the names I "know" so well!

 

And My apologies to the moderators for this massive cross posting, probably
won't happen again anytime soon, I hope. <wink wink>

 

Cheers, Thomas Janstrom.

Little Gems.

 <http://tjlittlegems.com/index.htm> http://tjlittlegems.com 

http://www.pbase.com/praxis178/root 


From arjan.te.marvelde at hetnet.nl  Mon Apr 27 05:25:21 2009
From: arjan.te.marvelde at hetnet.nl (Arjan te Marvelde (hetnet))
Date: Sun, 26 Apr 2009 22:25:21 +0200
Subject: [ATM] Low iron float glass
Message-ID: <49F4C331.6020708@hetnet.nl>


Has anybody on the list experience with making refractive optics using 
low iron float glass, such as specified here:

  http://uk.saint-gobain-glass.com/upload/files/sgg_diamant_.pdf

It seems like a cheap alternative, for example to be used for 
full-aperture correctors like Lurie-Houghton, Maksutov or Schmidt 
Cassegrain.

   Arjan

From foreilly at verizon.net  Mon Apr 27 05:44:12 2009
From: foreilly at verizon.net (Francis J. O'Reilly)
Date: Sun, 26 Apr 2009 16:44:12 -0400
Subject: [ATM] warning: Massive cross posting,
 slightly OT: My impending visit to the USA.
References: <027801c9c66d$23443fa0$69ccbee0$@com>
Message-ID: <E6B34B7C3E584DA8A8ACF1CCD323DCC1@HELENYLCMWAV95>

Tom,

If you find yourself in NY, drop me an email.

Stellafane is 8/13-8/16

Francis J. O'Reilly
----- Original Message ----- 
From: "Thomas Janstrom" <thomas at moiler.com>
To: <atm_free at yahoogroups.com>; <atm at atmlist.net>; 
<Digital-Rebels at yahoogroups.com>; <Knappers-R-Us at yahoogroups.com>; 
<glassblowing_topics at yahoogroups.com>; <usfgfaceterslist at yahoogroups.com>; 
<Mirror-O-Matic at yahoogroups.com>
Sent: Sunday, April 26, 2009 8:47 AM
Subject: [ATM] warning: Massive cross posting,slightly OT: My impending 
visit to the USA.


> Hi everyone,
>
>
>
> Just a note to let everyone know that I'll be visiting the USA for three
> months (quite a few of you already know this), this message is just to let
> everyone else know some of the basic in case anyone else wants to catch up
> with me at some point.
>
>
>
> I'll be arriving in country on the 6th of May, and for May my time is 
> mostly
> my own, I'll be doing a course of studies at a school in Florida for all 
> of
> June, and then July is again mine to squander as I see fit. So if you're 
> in
> the South East of the US, and want to catch up, drop me a line and we can
> see about working out the details.
>
>
>
> I'd really like to put some faces to all the names I "know" so well!
>
>
>
> And My apologies to the moderators for this massive cross posting, 
> probably
> won't happen again anytime soon, I hope. <wink wink>
>
>
>
> Cheers, Thomas Janstrom.
>
> Little Gems.
>
> <http://tjlittlegems.com/index.htm> http://tjlittlegems.com
>
> http://www.pbase.com/praxis178/root
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 



From daze39 at earthlink.net  Mon Apr 27 07:39:52 2009
From: daze39 at earthlink.net (David Weinshenker)
Date: Sun, 26 Apr 2009 15:39:52 -0700
Subject: [ATM] Low iron float glass
In-Reply-To: <49F4C331.6020708@hetnet.nl>
References: <49F4C331.6020708@hetnet.nl>
Message-ID: <49F4E2B8.10505@earthlink.net>

Arjan te Marvelde (hetnet) wrote:
> Has anybody on the list experience with making refractive optics using 
> low iron float glass, such as specified here:
> 
>   http://uk.saint-gobain-glass.com/upload/files/sgg_diamant_.pdf
> 
> It seems like a cheap alternative, for example to be used for 
> full-aperture correctors like Lurie-Houghton, Maksutov or Schmidt 
> Cassegrain.

I'm not sure how cheap it is relative
to BK7, but I suspect "Borofloat"
might work well for that sort of thing.

-dave w

From atmer at flash.net  Mon Apr 27 07:54:44 2009
From: atmer at flash.net (Anthony Stillman)
Date: Sun, 26 Apr 2009 15:54:44 -0700 (PDT)
Subject: [ATM] Low iron float glass
In-Reply-To: <49F4E2B8.10505@earthlink.net>
References: <49F4C331.6020708@hetnet.nl> <49F4E2B8.10505@earthlink.net>
Message-ID: <459477.19134.qm@web82001.mail.mud.yahoo.com>


The refractive homogeneity of borofloat can be (is often) quite poor.  The glass should be from the same batch and check it before you start grinding.



----- Original Message ----
From: David Weinshenker <daze39 at earthlink.net>
To: "atm at atmlist.net" <atm at atmlist.net>
Sent: Sunday, April 26, 2009 3:39:52 PM
Subject: Re: [ATM] Low iron float glass

Arjan te Marvelde (hetnet) wrote:
> Has anybody on the list experience with making refractive optics using 
> low iron float glass, such as specified here:
> 
>   http://uk.saint-gobain-glass.com/upload/files/sgg_diamant_.pdf
> 
> It seems like a cheap alternative, for example to be used for 
> full-aperture correctors like Lurie-Houghton, Maksutov or Schmidt 
> Cassegrain.

I'm not sure how cheap it is relative
to BK7, but I suspect "Borofloat"
might work well for that sort of thing.

-dave w
_______________________________________________
ATM mailing list http://www.atmlist.net/


From daze39 at earthlink.net  Mon Apr 27 08:30:32 2009
From: daze39 at earthlink.net (David Weinshenker)
Date: Sun, 26 Apr 2009 16:30:32 -0700
Subject: [ATM] Low iron float glass
In-Reply-To: <459477.19134.qm@web82001.mail.mud.yahoo.com>
References: <49F4C331.6020708@hetnet.nl> <49F4E2B8.10505@earthlink.net>
	<459477.19134.qm@web82001.mail.mud.yahoo.com>
Message-ID: <49F4EE98.8020607@earthlink.net>

Anthony Stillman wrote:
> The refractive homogeneity of borofloat can be (is often) quite poor. 
> The glass should be from the same batch and check it before you start
> grinding.

Hmmm... are you referring to non-uniformity within a single sheet, or
variations between different batches?

-dave w

From atmer at flash.net  Mon Apr 27 09:20:06 2009
From: atmer at flash.net (Anthony Stillman)
Date: Sun, 26 Apr 2009 17:20:06 -0700 (PDT)
Subject: [ATM] Low iron float glass
In-Reply-To: <49F4EE98.8020607@earthlink.net>
Message-ID: <843257.90224.qm@web82001.mail.mud.yahoo.com>


Both

David Weinshenker wrote: 
> Anthony Stillman wrote:
>> The refractive homogeneity of borofloat can be (is often) quite poor. 
>> The glass should be from the same batch and check it before you start
>> grinding.
> Hmmm... are you referring to non-uniformity within a single sheet, or
> variations between different batches?
> -dave w


From tom_krajci at tularosa.net  Mon Apr 27 11:39:11 2009
From: tom_krajci at tularosa.net (Tom Krajci)
Date: Sun, 26 Apr 2009 20:39:11 -0600
Subject: [ATM] Heat rope suppliers
In-Reply-To: <mailman.186.1240647777.10065.atm@atmlist.net>
References: <mailman.186.1240647777.10065.atm@atmlist.net>
Message-ID: <49F51ACF.4060608@tularosa.net>

Thanks for all the suggestions!

Now I can find a supplier of bulk length heat rope, which will come in 
handy as I set up more scopes on my photometry farm.

-- 
-------------------------------------------
Tom Krajci
Cloudcroft, New Mexico
http://picasaweb.google.com/tom.krajci

Center for Backyard Astrophysics (CBA)
http://cbastro.org/ CBA New Mexico

American Association of Variable Star
Observers (AAVSO): KTC http://www.aavso.org/
-------------------------------------------


From thomas at moiler.com  Mon Apr 27 11:57:48 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Mon, 27 Apr 2009 12:57:48 +1000
Subject: [ATM] seeing something I've never seen before when testing.....
Message-ID: <018301c9c6e3$f44d9210$dce8b630$@com>

Ok, so I put  16.5" mirror on the test stand and after half an hour of
fiddling to line everything up at the predicted location I'm not seeing what
I expected to see. Istead I see a "ghost" of my light source ~1300mm in
front of the tester, perfectly in focus just floating in mid air..

 

So just what am I seeing?

 

The mirror's ROC is 3380mm (plus or minus 5mm or so, I expect by this stage
of polishing), and should be a sphere.

 

Cheers, Thomas Janstrom.

Little Gems.

 <http://tjlittlegems.com/index.htm> http://tjlittlegems.com 

 


From wa4guu at verizon.net  Mon Apr 27 12:19:31 2009
From: wa4guu at verizon.net (Jerry)
Date: Sun, 26 Apr 2009 23:19:31 -0400
Subject: [ATM] seeing something I've never seen before when testing.....
In-Reply-To: <018301c9c6e3$f44d9210$dce8b630$@com>
Message-ID: <DBAB6BD9CBD1482CB5A87E28FFBD42D8@D85SJB21>

Hello Thomas

Seems to me your actual ROC is about 2730 mm.

Jerry

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Thomas Janstrom
Sent: Sunday, April 26, 2009 10:58 PM
To: Mirror-O-Matic at yahoogroups.com; atm_free at yahoogroups.com;
atm at atmlist.net
Subject: [ATM] seeing something I've never seen before when testing.....

Ok, so I put  16.5" mirror on the test stand and after half an hour of
fiddling to line everything up at the predicted location I'm not seeing what
I expected to see. Istead I see a "ghost" of my light source ~1300mm in
front of the tester, perfectly in focus just floating in mid air..

 

So just what am I seeing?

 

The mirror's ROC is 3380mm (plus or minus 5mm or so, I expect by this stage
of polishing), and should be a sphere.

 

Cheers, Thomas Janstrom.

Little Gems.

 <http://tjlittlegems.com/index.htm> http://tjlittlegems.com 

 

_______________________________________________
ATM mailing list http://www.atmlist.net/


From thomas at moiler.com  Mon Apr 27 15:30:17 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Mon, 27 Apr 2009 16:30:17 +1000
Subject: [ATM] Ronchi test images of my cast cellular 16.5" mirror.
Message-ID: <000601c9c701$a6645de0$f32d19a0$@com>

http://www.pbase.com/praxis178/hobbies first two. The first image is the
second of the two and the mirror was rotated 90 degrees from the first, I
also reduced the number of lines visible.

 

Short of the VERY obvious effects of the vanes of divitrification in the
blank the surface is not too bad for my first attempt at machine polishing. 

 

I can't pick any print through from the cells, and when I took a look via
Foucault there was plenty of surface roughness, but again no print through,
and I went way faster than I planned to with the curve as polished (I didn't
want to go faster than F/4) being F/3.21. So I'll chalk this one up as
another successful step down the road to a light weight cast cellular mirror
in a scope of mine someday.

 

Next step (later this year, for obvious reasons) is to cast another blank,
this time without the devit' problems! <grin>

 

I may still try a bit of figuring on this blank if only for the experience
and chance to learn a new skill with little to be risked.

 

Cheers, Thomas Janstrom.

Little Gems.

 <http://tjlittlegems.com/index.htm> http://tjlittlegems.com 

 


From dlwebb at canit.se  Mon Apr 27 17:44:47 2009
From: dlwebb at canit.se (Dominic-Luc Webb)
Date: Mon, 27 Apr 2009 10:44:47 +0200 (MET DST)
Subject: [ATM] Low iron float glass
In-Reply-To: <49F4C331.6020708@hetnet.nl>
Message-ID: <Pine.LNX.4.44.0904271021120.15080-100000@uno.canit.se>


On Sun, 26 Apr 2009, Arjan te Marvelde (hetnet) wrote:

>
> Has anybody on the list experience with making refractive optics using
> low iron float glass, such as specified here:
>
>   http://uk.saint-gobain-glass.com/upload/files/sgg_diamant_.pdf
>
> It seems like a cheap alternative, for example to be used for
> full-aperture correctors like Lurie-Houghton, Maksutov or Schmidt
> Cassegrain.
>
>    Arjan


I am using "Optiwhite" from Glaverbel in Belgium for Schmidt
correctors. The original link still goes to a glass website,
but looks like new name (don't know what that means):

http://www.agc-flatglass.eu/

Most glass shops have small samples of Optiwhite that are
perfectly clear and it is specified as low iron. The
"low iron" term is very vague. Note the actual glass I
received. I complained about it, but they were not willing
to replace it, stating that they do not guarantee the
result will actually be completely clear. Looking through
the surface, Optiwhite looks colorless. However, as you
can see from these pics on my 310 mm Schmidt website,
looking on end, the glass definitely has a green tint,
albeit less than common plate glass:

http://www.canit.se/~dlwebb/catadioptric/310schmidt/corr_col.jpg
http://www.canit.se/~dlwebb/catadioptric/310schmidt/glass.jpg

This is good glass to experiment with for making Schmidt
correctors. It can be had around 6 mm thickness and is quite
cheap. Based on that second flgure from my website, I would say
the Gleverbel glass, despite the green tint, competes rather well
with a high-end polished borosilicate produced for optical
applications (precision made microscope cover slip). With regard
to how to obtain it, this glass has a very wide distribution in
Europe. It can be ordered from pretty much any local glass shop.
At least here in Sweden, the word "Optiwhite" was pretty well
known to the glass shops.

Regarding batch variability, this is not optical glass. As
indicated above, you will have to accept more batch variability
and likkely even variability within same glass. So far, I have
not found anything disastrous, like fracture lines that would
make the glass easy to break using the vacuum pan technique,
for instance. However, I am working on a turntable technique. I
know professional optical labs have used turntables, so it is
possible.

Thickness: This is still a problem in Europe. The thick plate
glass I have found was of no consequence to me because the
precision annealed optical glass (e.g., BK7) in the USA would
have been cheaper. I have heard of factories in Taiwan and
Eastern Europe producing more affordable glass, but have not
purchased anything myself thus far. Asian factory I once
encountered had no interest in small orders. I think anything
less than a shipping container per year was entirely out of
the question.


Dominic-Luc Webb


From daze39 at earthlink.net  Mon Apr 27 18:08:08 2009
From: daze39 at earthlink.net (David Weinshenker)
Date: Mon, 27 Apr 2009 02:08:08 -0700
Subject: [ATM] Low iron float glass
In-Reply-To: <Pine.LNX.4.44.0904271021120.15080-100000@uno.canit.se>
References: <Pine.LNX.4.44.0904271021120.15080-100000@uno.canit.se>
Message-ID: <49F575F8.6000900@earthlink.net>

Dominic-Luc Webb wrote:
> Most glass shops have small samples of Optiwhite that are
> perfectly clear and it is specified as low iron. The
> "low iron" term is very vague. Note the actual glass I
> received. I complained about it, but they were not willing
> to replace it, stating that they do not guarantee the
> result will actually be completely clear. Looking through
> the surface, Optiwhite looks colorless. However, as you
> can see from these pics on my 310 mm Schmidt website,
> looking on end, the glass definitely has a green tint,
> albeit less than common plate glass:

I've obtained some small disks of Borofloat from www.mcmaster.com
(sold as industrial sight glass) to try out grinding and polishing
(before attempting an actual optical element for a project I really
cared about)... the "edge color" is pretty subtle compared to most
other glass I've seen, without the distinctive greenish tint of
common float glass or the yellowish or grayish tint of "Pyrex"
brand borosilicates... I'd call it very nearly "water white".

As for uniformity, I know that Schott advertises it as a feature
of the Borofloat glass; presumably this is by comparison to the
usual standards for window glass, not optical glass (which would
be made to more exact specifications for refractive index).

-dave w

From al at sgi.com  Mon Apr 27 21:03:37 2009
From: al at sgi.com (Alexis Cousein)
Date: Mon, 27 Apr 2009 14:03:37 +0200
Subject: [ATM] Low iron float glass
In-Reply-To: <Pine.LNX.4.44.0904271021120.15080-100000@uno.canit.se>
References: <Pine.LNX.4.44.0904271021120.15080-100000@uno.canit.se>
Message-ID: <49F59F19.3030105@sgi.com>

Dominic-Luc Webb wrote:
> On Sun, 26 Apr 2009, Arjan te Marvelde (hetnet) wrote:
> 
>> Has anybody on the list experience with making refractive optics using
>> low iron float glass, such as specified here:
>>
>>   http://uk.saint-gobain-glass.com/upload/files/sgg_diamant_.pdf
>>
>> It seems like a cheap alternative, for example to be used for
>> full-aperture correctors like Lurie-Houghton, Maksutov or Schmidt
>> Cassegrain.
>>
>>    Arjan
> 
> 
> I am using "Optiwhite" from Glaverbel in Belgium for Schmidt
> correctors. The original link still goes to a glass website,
> but looks like new name (don't know what that means):
> 
> http://www.agc-flatglass.eu/

Glaverbel has had Asahi Glass Co. as its main shareholder since 1981;
some time ago they assumed full control and renamed it AGC Flat Glass
Europe.


From rmay at nethere.com  Tue Apr 28 06:00:47 2009
From: rmay at nethere.com (Bob May)
Date: Mon, 27 Apr 2009 14:00:47 -0700
Subject: [ATM] seeing something I've never seen before when testing.....
References: <018301c9c6e3$f44d9210$dce8b630$@com>
Message-ID: <001c01c9c77b$41c98340$8f78fea9@amd>

By "ghost", I assume that is where you see a focused light spot.
If so, I'll agree with Jerry as to about where the ROC is.
Spherometers, if not calibrated properly, can be way off from
what you think that they are reading.  I've taken plate glass
(usually flat to a fair degree) and had to grind it to get it
flat enough to indicate correctly a flat surface.  This gets
especially bad when large ROCs are measured.  I've seen plate be
as much as a half a thousandth off from flat over a 4"
spherometer diameter.
For reference, when setting up a Foucault or Ronchi test, I use a
"finder" LED that is a really bright LED that just shines on the
target mirrror and returns a beam to another spot on the face of
the tester KE plane.  This LED is used to find the approximate
focus (just make the spot as small as it will go by changing the
ROC position) and then put it at a particular precalibrated spot
which should put the KE LED at the right spot to see the return
from the mirror for the test.  Since I use a camera to see the
test rather than my eye, the finder LED is quite necessary to
have to get the system setup to put the returned beam into that
little hole that is the lens.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net



From mbartels at bbastrodesigns.com  Tue Apr 28 11:15:54 2009
From: mbartels at bbastrodesigns.com (Mel Bartels)
Date: Mon, 27 Apr 2009 19:15:54 -0700
Subject: [ATM] [atm_free] Ronchi test images of my cast cellular 16.5"
	mirror.
In-Reply-To: <000601c9c701$a6645de0$f32d19a0$@com>
References: <000601c9c701$a6645de0$f32d19a0$@com>
Message-ID: <004301c9c7a7$49c3e2d0$dd4ba870$@com>

>>>I can't pick any print through from the cells, and when I took a look via
Foucault there was plenty of surface roughness, but again no print through

 

 

I don't want to rain on you parade, but I see strong print through effects.
L

 

Mel Bartels

 

 


From radicell2 at yahoo.com  Tue Apr 28 22:18:32 2009
From: radicell2 at yahoo.com (Ric Rokosz)
Date: Tue, 28 Apr 2009 06:18:32 -0700 (PDT)
Subject: [ATM]  OT  Free Yahoo Geocities closing down
Message-ID: <917612.23523.qm@web34507.mail.mud.yahoo.com>


Pass the word that later this year Yahoo Geocities will be closing down.
Lots of good sites will be gone unless owners save their material.

Ric


      __________________________________________________________________
Get a sneak peak at messages with a handy reading pane with All new Yahoo! Mail: http://ca.promos.yahoo.com/newmail/overview2/

From thomas at moiler.com  Tue Apr 28 22:24:47 2009
From: thomas at moiler.com (Thomas Janstrom)
Date: Tue, 28 Apr 2009 23:24:47 +1000
Subject: [ATM] OT  Free Yahoo Geocities closing down
In-Reply-To: <917612.23523.qm@web34507.mail.mud.yahoo.com>
References: <917612.23523.qm@web34507.mail.mud.yahoo.com>
Message-ID: <032401c9c804$b4843f40$1d8cbdc0$@com>

One of the reasons I moved my site last year to a private hosting
service.... That and I got sick of the ads and such.

BTW if a few people need somewhere to temporarily host their site because of
this, drop me a line and we can discuss it, but please do so off list! 

Cheers, Thomas Janstrom.
Little Gems.
http://tjlittlegems.com 


-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Ric Rokosz
Sent: Tuesday, 28 April 2009 11:19 PM
To: atm at atmlist.net
Subject: [ATM] OT Free Yahoo Geocities closing down


Pass the word that later this year Yahoo Geocities will be closing down.
Lots of good sites will be gone unless owners save their material.

Ric


      __________________________________________________________________
Get a sneak peak at messages with a handy reading pane with All new Yahoo!
Mail: http://ca.promos.yahoo.com/newmail/overview2/
_______________________________________________
ATM mailing list http://www.atmlist.net/


From stainless_steel at suddenlink.net  Wed Apr 29 04:21:39 2009
From: stainless_steel at suddenlink.net (stainless_steel at suddenlink.net)
Date: Tue, 28 Apr 2009 14:21:39 -0500
Subject: [ATM] seeing something I've never seen before when testing.....
In-Reply-To: <018301c9c6e3$f44d9210$dce8b630$@com>
References: <018301c9c6e3$f44d9210$dce8b630$@com>
Message-ID: <2310E568BEDB41958821CF89A319ACCA@R101>

Thomas,

You are seeing an aerial image of the light source or slit. Your tester is 
exactly half of the distance away from  the perceived location, and the 
desired location.

DLZ-130


----- Original Message ----- 
From: "Thomas Janstrom" <thomas at moiler.com>
To: <Mirror-O-Matic at yahoogroups.com>; <atm_free at yahoogroups.com>; 
<atm at atmlist.net>
Sent: Sunday, April 26, 2009 9:57 PM
Subject: [ATM] seeing something I've never seen before when testing.....


> Ok, so I put  16.5" mirror on the test stand and after half an hour of
> fiddling to line everything up at the predicted location I'm not seeing 
> what
> I expected to see. Istead I see a "ghost" of my light source ~1300mm in
> front of the tester, perfectly in focus just floating in mid air..
>
>
>
> So just what am I seeing?
>
>
>
> The mirror's ROC is 3380mm (plus or minus 5mm or so, I expect by this 
> stage
> of polishing), and should be a sphere.
>
>
>
> Cheers, Thomas Janstrom.
>
> Little Gems.
>
> <http://tjlittlegems.com/index.htm> http://tjlittlegems.com
>
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/


--------------------------------------------------------------------------------



No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.287 / Virus Database: 270.12.6/2084 - Release Date: 04/28/09 
06:15:00