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


Harold:

I think that in my design, the orings press into the sponge rings and there
is little inward deformation.  The "used" sponge rings that I
replaced during trials to get the height right were deformed into hourglass
shaped cross section due to the orings being pressed into them.

The idea of a perimeter restraint would be to keep the very circular mirror
on a very circular cushion.  In Adler's program, there is a number
generated that shows the limit of the uniformity of the cushion in percent.

I cannot say how much these numbers affect the final figure.  I was out
with my 8" f/7 flex scope near new years and saw the Enke division for
the first time.  Seeing was rare.  I have never adjusted the figure
(tension) since last year. Star test patterns are perfect.  There is
thermal current drifting off the surface which goes away.  If I put my fan
on it, that too would go away.

If you restrict the outer cushion unevenly then I'd imagine the uniformity
value gets out of tolerance and it may cause astig.  It's got to be as
uniform as you can get it.  4 evenly spaced points might be fine. The
weight of the mirror is not an issue.  The mirror seems to stay there, with
no noticeable side sag when tilted.

colin

-----Original Message-----
From: Harold [mailto:adams{at}rmci.net]
Sent: Saturday, January 11, 2003 4:26 PM To: CSC; Atm
Subject: flex mirror cell wall




>   Unless you can constrain the perimeter cushion into a perfect circle as
in
> my cake pan design, and locate the mirror exactly on it, >

  Colin.
  I would imagine the sponge walls might swell out at the side when
compressed. Does the inner sponge wall deform excessivly when it's outer
wall is restricted? If so, is it not a problem?

   I like your wall idea but being i didn't have a way to grove my plate and
the fact the o-ring/sponge is already glued, i am considering instead to
support the lower part of the o-ring/sponge/mirror with two post's/ledges
fixed to the plate, sort of like the mirror support in a focault test
stand. I am thinking this will keep the mirror and sponge wall from sagging
when the scope is in a less than vertical position. I am assumming that
although the mirror is pulled tight against the sponge that it will droop
some due to gravity when horizantal. Correct? Perhaps instead of one solid
wall i could use 4 posts around the mirror to better contain the sponge.
Any thoughts concerning this?

  Harold

  harold

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