Re: [ATM] Flexed Mirrors

[Jeff Rowe <jeffrowe@austin.rr.com>]

Friends;
Our old friend Frank Ward reported edge problems on a 12" mirror he was 
polishing, by not having his bottem support pad totally cover the bottem 
of his blank. Folks have reported the effects of petal laps and "zulu 
laps" as well as the effects of PLOP. Has anyone tried using a bullseye 
shaped pad (mouse pad like material) under their mirrors when polishing, 
the idea being the center and edge would be raised by this support and 
receive the most work, and the 60% zone would be void of support, and 
receive the least? A standard sphere stroke could be employed. Of 
course, plenty of rotation of blank and tool would desired to have the 
benefit of the random factor. This might do away with the need for pumps 
etc. Just a thought.
JR

G Gagne wrote:

>The recent posts by Bill Kelley and others have got me interested again 
>in my own flexed mirror project. Some time ago, I investigated making a 
>light weight 12" telescope. I procurred a 12" x 1" plate glass disc and 
>proceeded to grind and polish for a f/5.6 mirror. So far, it is almost 
>fully polished. The back has also been fine ground to a 135" radius with 
>a maximum wedge of .0011". The required tension for a paraboloid figure 
>is 69.7 lbs. or 0.62 psi.
>  
>

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