Re: [ATM] [atm_free] Re: The 16 inch Ultrathin ronchi pics

["Stephen Koehler" <s.c.koehler@gmail.com>]

Ric,

> Aren't you inducing a heck of a
> lot of additional astig into the equation just by
> virtue of this seperation.So much so that it skews all
> your results?

Since I worked with Dale's data, I will make a couple of points.  Yes,
Bath introduces astigmatism to some degree, but the analysis I did to
separate out test stand aberrations lumps the interferogram
astigmatism with the test stand aberratoins (as long as it doesn't
change much from run to run).  So, the interferogram astigmatism
polluted the reported test stand aberrations, but not the reported
mirror aberrations.  I think this is clearly demonstrated by my
graphic in Dale's report that shows mirror asymmetries rotating in
22.5 degree increments.

There remains the question of how much the of reported test stand
deformations were contributed by Bath interferometer astigmatism.  I
don't recall how large the Bath astigmatism is, but I think it is much
smaller than the test stand astigmatism we were seeing.  Perhaps Dale
has more specific details of this from his experience with the
interferometer.

--
Steve Koehler
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