Re: Re:ATM Cassegrain as second telescope project.

["Bob May" <bobmay@nethere.com>]

Actually Bill, the coma in a Cassegrain is dependent upon it's set of curves
used with the proper Ritchey-Chretien design being 0 coma.  On the other
hand, the one with the spherical primary (no corrector) will produce a lot
more coma than an equivalent Newt.
If you go past the RC design, you can even have inverse coma!
The Cass designs do suffer from other problems although the general rule is
that anything around the RC set of curves will produce a lot less error than
a Newt. will.
I wonder what a Schmidt corrector version of the primary for the RC would do
for performance?
Bob May
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bobmay@nethere.com
NEW! http://bobmay.astronomy.net