Re: [ATM] Test stand astig., edge support

[Michael Peck <mpeck1@ix.netcom.com>]

At 14:04 7/12/05, Mike Lockwood wrote:

>What I am curious of is whether absolutely ALL the test stand astigmatism 
>can be modeled with A22, or if there are smaller amounts of higher order 
>astigmatism underlying it.  While I respect the analysis of the data, I 
>find it hard to believe that all of the deformation is merely a change in 
>ROC, and I don't think the data in the report proves it, and certainly not 
>for thinner mirrors.
>

In the one sample of interferometric data I've looked at that actually 
showed evidence of test stand astigmatism there were some higher order 
astigmatism components mixed in - mostly 5th order aka secondary 
astigmatism. The total contribution of higher order defects was on the 
order of 0.01 waves rms, while the primary astigmatism component was over 
0.05 waves. I kind of doubt that most people do Foucault testing with 
enough precision for this amount of higher order astigmatism to be a problem.

I don't remember Steve quantifying the amount of higher order test stand 
defects in his writeup on the Milligan mirror's interferometry, but just 
from looking at his wavefront maps there was clearly a little more going on 
than just primary astigmatism.

Mike Peck


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Michael Peck
email mpeck1@ix.netcom.com
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