Re: [ATM] correction -+

["KR" <kreid@primus.ca>]

Thanks Dale
I'm using Dave Rowes Figure XP and foucault instrument. I had a difficult 
time getting the centre down until i made a small tool. The centre is rough 
but covered by the secondary. So it's relatively smooth.
    The foucault results say the closest ROC is +.005. So I'm thinking that 
conic must be Strehl=1. If I live another century, I might even try 
interferometry.
Thanks Dale, jerry.
    Ken
----- Original Message ----- 
From: "Dale Eason" <atmpob@yahoo.com>
To: "KR" <kreid@primus.ca>; <atm@atmlist.net>
Sent: Friday, June 22, 2007 8:38 PM
Subject: Re: [ATM] correction -+


> 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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>>
>
>
>
>
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