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Re: [ATM] Another Astigmatism question, but at the sphere

Mike, thanks for your answer to this, which was a rather reassuring one.
 
My most recent update on this thing is that my second star test session last night revealed an elliptical asymmetry along the same direction that my first set of star tests did, even though I had rotated the mirror 120 degrees after the first set.  So I'm pretty sure the problem is with the diagonal.  Think I'll loosen up the sleeve around the diagonal just a tad.  Anyway, it's probably time to parabolize (for the third time!).
 
Thanks,
Jay
 
 
Date: Sun, 28 Aug 2005 09:06:39 -0500
From: Michael Peck <mpeck1@ix.netcom.com>
Subject: Re: [ATM] Another Astigmatism question, but at the sphere
	stage
To: atm@atmlist.net
Message-ID: <6.2.3.4.2.20050828085822.035a4790@popd.ix.netcom.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 19:47 8/27/05, J Killea wrote:
>
>HOWEVER, I just did three sets of Foucault measurements along each 
>of 2 diameters and Sixtests (set to "Target b=0" with variable ROC 
>calculation) came back with the ROCs of each diameter differing by 
>about 0.5mm.  That's more delta than what I had when I thought my 
>parabola was done the first time.
>
>My question is whether it's too early to judge astigmatism, since 
>I'm only at the sphere stage, and whether Sixtests with Foucault 
>data is even a valid way to judge astigmatism.  I might just stick 
>it back in the 'scope

Where is everybody? I can't believe nobody has offered a helpful 
response after over 12 hours. Anyway, those radius of curvature 
estimates returned by sixtests and figurexp have no particular 
physical significance and certainly shouldn't be used to judge 
astigmatism. If those were my programs I wouldn't even report those 
numbers since people are easily misled by them.

I believe the tests of choice for detecting astigmatism in a 
spherical mirror are ronchi, or perhaps an artificial star created 
with a ball bearing as described in Tex.

>
>Is it time to go back to AlOx #15 or 20?  (Please say it ain't so!)

No.

Mike Peck



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