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

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

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



_________________

Michael Peck
email mpeck1@ix.netcom.com
Wildlife photoblog! http://wildlife-pix.com
Amateur telescope making http://home.earthlink.net/~mlpeck54/astro/astro.html 

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