Re: [ATM] Updated web site: mirror testing and Draper machine

["matt" <mariusrf@bellsouth.net>]

Bill,
How does it work out for small central obstructions ? It appears the center
is where the worst figure errors are , and if the area is not shaded by a
significant enough secondary, things deteriorate rapidly.
Does the mirror hold its figure with temp changes ? I played a little with
the flex program and it looks like the back tension has a real sharp optimum
peak, not a lot of leeway to maintain a good figure. With temperature
changes the elastic elements that are used to support the mirror change and
presumably the back tension changes too , or not ? I'm very interested to
learn more .

thanks,
matt tudor

-----Original Message-----
From: Bill Kelley <flex@commspeed.net>
To: Mike Spooner <spoon@PageAmerica.net>; Ric Rokosz <radicell2@yahoo.com>;
scott <srychnov@chem.ps.uci.edu>; atm@atmlist.net <atm@atmlist.net>
Date: Tuesday, November 30, 2004 10:23 PM
Subject: Re: [ATM] Updated web site: mirror testing and Draper machine


>List,
>Some reasonable argument can be made here for flex mirrors. We make them of
>plate glass and field tweak them for the conditions. Exquisitely smooth
>spheres are easy, and a Foucault null beats parabolizing and zonal testing.
>Before I get flamed, yes, I also parabolize mirrors occasionally- usually a
>replacement mirror for someone.
>Bill Kelley
>


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