Re: [ATM] figuring an ultra-thin 16" mirror

[Jim Burrows <burrjaw@earthlink.net>]

At 2004-06-03 17:47 +0200, Yan Greiling wrote:

>This mirror is made out of plate glass, it is f/4.5 and the center thickness
>is 1/2 inch.
>I have tried to figure it using the "classic" method (at least in France):
>full size tool, mirror on TOP, long wide strokes. But I could never achieved
>more than 8mm of difference of radius between inner and outer zones, while I
>need 11mm. The mirror may be too light, or too flexible.

I have absolutely no experience on such mirrors, but I'd guess that MOT 
wouldn't be a good idea because the mirror would bend over the edge of the 
tool, producing effects unknown to old experts used to standard 1/6 
thickness mirrors.  Probably best to have the mirror on its back (on a good 
substrate - newspapers? carpet?), and try Texereau's "C method of accented 
pressure" on p. 97.  He says it worked on an f/4.  Try that for a while and 
if the figure doesn't cooperate, go to "B method of the small tool", which 
is an effective, but slow, method.

         -- Jim Burrows
         -- mailto://burrjaw@earthlink.net
         -- http://home.earthlink.net/~burrjaw
         -- Seattle N47.4723 W122.3662 (WGS84) 

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