Re: [ATM] Not quite immaculate

[ArtfulBodger <artfulbodger@earthlink.net>]

Vladimir Galogaza wrote:

> In my opinion what you expect from experienced 
> people is mere wishful thinking.  To judge what 
> is wrong with a mirror and your procedure from 
> only few words about it, would be witchcraft.

My question is a general one, so I've asked it in broad terms.  It's 
not "how do I fix this mirror," it's "what kind of thing might cause 
an error like this?"  The question may not be answerable, but anyway 
it's not about hard facts.  Interferograms and Strehl numbers are 
irrelevant.

> Who made  computerised Foucault tester you have used?

Someone on this list.  It's a nice rig: a video camera collects 
images, a computer drives the knife and reads the numbers zone by 
zone.  The numbers get thoroughly crunched, and then the system tells 
you about your mirror.

I don't have all the data handy.  On one axis, the mirror tests out 
at about 1/16 wave PV; on the perpendicular axis, it's 1/9 wave.  The 
several readings taken between these axes are comparable, except for 
this one spot that reads 1/3.9 or so.  The bad spot is narrow; it 
shows a buggered edge; I wonder how I did it.

Too vague?  Um ... yeah, could be.

>  Otherwise what you can expect is pure guessing.

Fine with me: that's exactly what I'm after, the guesses of 
experienced mirrormakers.

Pete

-- 
Artful Bodger
http://www.artfulbodger.net
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