From: Clive Milne 
To: atm{at}shore.net
Reply-To: Clive Milne 



    It would be an interesting exercise for those that had
interferograms supplied with their optics to see if it was in fact for the
entire radius of the optic,  or  has the outer 5% of the optic
been masked to exclude a turned edge from the data?

   ~Clive.

> I note also that the section showing what `terms'  have been removed from
> the data has been chopped off the printout  ie focus , astigmatism. . I'm
> well familiar with what  Zygo `Zap' software printouts should look like in
> completeness.
>
> I would suspect from the three equispaced bumps on the phase map, that
> astigmatism has been subtracted too. This seems to be standard practice
> amongst companies offering interferograms, because of the astigmatism
> induced by self weight deformation, but I would question how much effort
> goes in to analyzing how much real astigmatism these mirrors might have,
> before it is `subtracted out'.



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