Re: [ATM] RE: 25" mirror possibilities

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

At 14:58 23-11-04, you wrote:

>But, what ATM books available today describe aplanatic Gregorian designs?
>That's where my point lies...unless you dig a good bit, and are willing to
>do your own design work...the starting amateur probably won't find out about
>this design.  That's too bad because with two concave surfaces it should be
>pretty easy to fabricate and test...especially compared to many other
>2-mirror scope designs.

Tom:

With proper sign conventions the formulas for Gregorian telescopes are 
exactly the same as for Cassegrains. Unfortunately the standard ATM 
reference on telescope design (R&vanV) doesn't discuss Gregorians in any 
detail, so most ATMs don't realize they are basically the same class of 
telescope.

Modern texts like Schroeder's "Astronomical Optics" or Wilson's "Reflecting 
Telescope Optics" treat all two mirror designs as a single family. Neither 
of those are aimed at ATMs, but in my opinion every serious ATM should own 
at least one of them.

Mike Peck


_________________

Michael Peck
email mpeck1@ix.netcom.com
Wildlife photography page http://home.netcom.com/~mpeck1/index.html
Amateur telescope making http://home.netcom.com/~mpeck1/astro/astro.html  

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