Re: [ATM] correction -+

[Dale Eason <atmpob@yahoo.com>]

For a 10 inch F5 assuming only spherical error a CC of
-1.065 is 1/29 RMS and -1.060 is 1/30 RMS on the
wavefront.  Not much difference.  

I computed this using my program OpenFringe and tried
different spherical zernike terms until I got a conic
of -1.060 and -1.065.

So if the mirror is smooth and has no zones then it is
good enough assuming the Strehl and RMS of the
Foucault data reduction agree.

Dale Eason

--- KR <kreid@primus.ca> wrote:

> Hello list,
> 
>     Twice I've asked myself, what value of
> correction is on the level of a 
> RMS value of 6, a PV of 1/13, strel .988?
> I don't recall any discussion on the matter. When
> you approach very good 
> readings, the temptation arises; I can't make it
> around the barrel again 
> without loosing good Foucault results, so the
> good-enough becomes relevant.
>     This is plate glass, f/6. If I do a set of
> readings in the morning when 
> it is warming up, they are different than an evening
> set when cooling. I 
> will continue to average readings, so far -1.06, but
> they have ranged 
> from -1.065 down to -1.06 (not really an average).
> If plate glass gives such 
> wide ranging results, I ask what value of correction
> weighs in with good 
> Foucault readings?
>     Star test will tell in the end. Does anyone have
> thoughts on this?
> Thanks   KMR 
> 
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> ATM mailing list http://www.atmlist.net/
> 



       
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