RE: [ATM] Another Astigmatism question, but at the sphere stage

["Jerry" <wa4guu@verizon.net>]

Can someone provide Foucault and Ronchi images of this astigmatic mirror?
Having seen astigmatism on a mirror under these tests I suspect that someone
was more interested in making zone measurements than in looking at the
entire figure without a mask. I cannot quantify the astigmatism that I saw
so I can't say if it was extreme or not. But it was removed quickly by only
exercising more attention to rotating the mirror on its support (carpet)
when it was on the bottom. This was done polishing so I don't think it was
extreme. My experience was with a 12.5" f6.

I would expect more difficulty seeing astigmatism on faster mirrors. And if
the surface is rough with much dog biscuit it might be more difficult but
that needs to be fixed even without astigmatism.


Jerry

-----Original Message-----
From: atm Guy Brandenburg
 
FWIW, about a dozen or so rather experienced ATMers
(including myself as 'very experienced' might be a
joke, I donno) tested 3 mirrors over the past 2 or 3
years in something that was called the Mirror Round
Robin (or something like that). Why do I mention this?
Because one of those mirrors was astigmatic, and IIRC,
NONE OF US CAUGHT THE ASTIGMATISM.



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