Re: ATM RE: flex mirror cell wall

["Bill Kelley" <flex@commspeed.net>]

Colin,Harold,

My experience has been that the sponge pusher ring works fine with or
without a retaining wall. I would not contain the ring with a couple of
posts
as in foucault testing. When viewing other than vertically the posts will be
pushing the ring in locally from the weight of the mirror- a good way to
 introduce some astigmatism.

Bill Kelley

----- Original Message -----
From: "CSC" <optic@gwi.net>
To: "Atm" <atm@shore.net>
Sent: Monday, January 13, 2003 9:06 PM
Subject: ATM RE: flex mirror cell wall


>
> 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@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
>
>
>
>
>
>