Re: [ATM] Schmidt Cassegrain

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

At 09:24 1/9/05, Richard F.L.R. Snashall wrote:
>This week's guessing game (305 mm f/8):
>
>    http://users.rcn.com/rflrs/f8asphere1-03x.len
>    http://users.rcn.com/rflrs/f8asphere1-03x.txt
>
>The attempt here is to use the corrector to reduce
>astigmatism.  It is not a Ritchey-Chretien.
>

Two oblate ellipsoids? I take it manufacturability isn't a major 
consideration in these design exercises. As you probably know R&vanV 
designed an "optimized" compact SCT that's approximately aplanatic with a 
prolate ellipsoidal secondary and slightly modified asphere on the corrector.

If you want to try an interesting guessing game how about reverse 
engineering Meade's new line of Ritchey-Chretien telescopes 
<http://www.meade.com/rcx400/>? They claim to correct astigmatism with a 
front corrector element, but from the information available it's not clear 
if it's a Schmidt like thin plate or a meniscus. I'm guessing it's a thin 
plate.

Mike Peck


------
Michael Peck
mpeck1@ix.netcom.com

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