Re: [ATM] astigmatism as seen via ronchi?

[Jim Burrows <burrjaw@earthlink.net>]

At 2008-03-03 04:10 -0800, Bob May wrote:

>Yeppie, it generally means a problem!
>Run the Ronchi closer to the ROC and get it to show just one line
>across half the mirror and you will see the S shape really bad.
>Is this what you're seeing with that Lurie-Houghton???

To see what a Ronchi test would show you with a given amount of astig 
on the mirror, download and run:

         http://home.earthlink.net/~burrjaw/public/diffract.zip 
(2004-04-12, Win32, 374.6 k)

I wrote this simulation in an (unsuccessful) effort to quantize the 
Ronchi test.  As Suiter, "Star Testing Astronomical Telescopes", says 
on p. 297, "But this test has a variable sensitivity that has been 
unappreciated or ignored by many advocates."

         -- Jim Burrows
         -- http://home.earthlink.net/~burrjaw
         -- mailto:burrjaw@earthlink.net
         -- Seattle N47.4723 W122.3662 (WGS84)

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