From: "MARY WINSTON" 
To: ray{at}stabilite.com
Cc: atm{at}shore.net
Reply-To: "MARY WINSTON" 


All,

Seems to me that there are four spincast Zerodur mirrors, 320" in
diameter, and a tad over 6.5" thick, sitting on the top of Paranal
Mountain in Northern Chil‚.  Now that is a diameter to thickness ratio of
46 to 1!! Seems to me Ray is illustrating just how far he has been able to
successfully push the thin mirror envelope for the ATM.




Coyot‚


>From: ray{at}stabilite.com (Ray Desmarais)
>Reply-To: ray{at}stabilite.com (Ray Desmarais)
>To: Mark Suchting 
>CC: atm{at}shore.net
>Subject: Re: ATM Too big, too thin
>Date: Thu, 27 Feb 2003 08:51:28 -0600 (CST)
>
>
>  Ray wrote:
>
> > > I have successfully made a 36" flat .9" thick, and
a 72" mirror .9 "
> >Thick.
>
>For the purposes of the discussion , lets get some perspective here . These
>big spherical mirror surfaces are basically reverse `Flux' collectors , not
>precision optical surfaces.
>
>~Mark
>
>Hi All,
>
>In reply to Mark
>
>I don't remember you being at the shop during manufacturing or testing of
>these surfaces. If you had been you would have discovered that the mirrors
>were made as an experiment to see what the limits were.
>The end users specifications were exceeded by a factor of at least 10
>times.
>This was an Ideal situation to see what is possible. This is one of the
>largest thinnest mirror ever made.
>The weak point in the system is in the cell to hold the mirror. The
>27-point
>cell holds the mirror to a few waves, which exceeds the specs by a factor
>of
>6 times.
>This was not my first dance; the intention of my post was to try to assist
>anyone who wants to proceed with a large thin mirror, and to pass on any
>info to reduce the learning curve for them.
>I am certain that the large mirror could have been corrected to better than
>1/2 wave {at} 633 nm with little effort. The problem is in supporting it in
>the
>scope at various angles.
>I have some of the best testing equipment in the industry, which makes it
>easy to scientifically evaluate what is going on.
>It is difficult to post on this list for me, I have an enormous amount of
>information to pass on and feel reluctant to do so.  I'm not saying that
>everyone should try and make a 72" diameter mirror that is
.9" thick for a
>telescope.
>I wanted to make my self available to pass on information to help people
>who
>are seriously considering making a large thin mirror, and to help them
>avoid
>the black holes that are out there.  I do not have a lot of time to read or
>post on the list. However I would like to help others who want to push the
>limits of optical fabrication.
>
>RAY
>Ray Desmarais
>479-890-4918
>ray{at}stabilite.com
>
>Education is not something that can be completed.
>It's a way of life.


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