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Re: [ATM] figuring an ultra-thin 16" mirror
I tried to parabolize larger mirrors with full size laps MOT in the past and
had similar problems.
I got more correction when cutting back the edges of the lap as Mel said, but
couldn't really control all zones to be equally parabolized.
Now I work Tool on ToP with 35-45% tools and W- strokes and have far better
control. Continous rotation and walking around is critical to prevent uneven
wear and astigmatism. The mirrors showed in the phase contrast test a very
smooth surface. Surface roughness I get only with very small tools (like 3").
See picture here parabolizing a 14" of 21 mm edge thickness with a 6" star
lap:
http://www.stathis-firstlight.de/atm/bilder/14parabolizing_1.jpg
and here parabolizing a 24" witha 10" star lap
http://www.stathis-firstlight.de/atm/bilder/parabolisieren_25cm.jpg
Stathis Kafalis
www.stathis-firstlight.de
----- Original Message -----
From: "GREILING Yan" <yan.greiling@eurocontrol.int>
To: <atm@atmlist.net>
Sent: Thursday, June 03, 2004 5:47 PM
Subject: [ATM] figuring an ultra-thin 16" mirror
> 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 wich to know if some of you have already encountered a similar problem.
>
> Yan Greiling
>
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