From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 



-----Original Message-----
From: Rick Maillet [mailto:bucko_62{at}yahoo.com]
Sent: Monday, July 28, 2003 11:28 PM To: CSC
Subject: RE: ATM 10" F9 mirror thickness


Hello Colin,

      I am in the process of making a 8.75"  1/2"
thick piece of plate into a mirror, shooting for about a 92" focal
lenght, I doubt I will need to worry about flexing it but am interested in
the process of flexing, Is there any sites on this that you know of that
might gleen more information, maybe i could shorten the focal lenght to
80" or so and try it out.

                                         Rick
Still  using that great pitch you sent to me before too, great stuff.



=====
Keep looking up,You just may see something interesting.

Rick:
Alan Adler wrote a great article Nov 2000 Sky & tel.  In a personal
note, he told me that 8" f/6 is a great formula for flexing.  Not too
steep, good magnification, small obstruction.  I chose f/7 to ease the
tolerances on my first flex. a 5mm radian eyepiece is superb with this f #.

Make the best sphere you can.   It is possible to be certain to 1/30 wavwe,
and to get it real smooth.  Make sure it is even thickness all around,
within a few thousandths. Build a cell and a puller which is a 4-6"
disk attached to the back of the mirror with a sponge rubber pad, and a
spring to maintain tension.  The mirror is supported around the edge, and
the pulling tension creates a high accuracy paraboloid.  It stays pretty
well at whatever correction you find via the star test.

Medium thin glass, 10" or less,  and a moderate f # are best. 
Probably get 1/10 to 1/20 final wavefront.

Colin

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