Re: [ATM] RE: 25" mirror possibilities

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

At 19:31 21-11-04, lou krajci wrote:

>True, but let's expand our 'design thinking' a bit outside the box.

That's not outside the box. All of the possible design variations involving 
two mirrors have been known for decades.

>Question for the group:  are there variants of the Gregorian (let's call
>them 'compensated Gregorians') that use a non-paraboloidal main mirror, but
>a concave secondary that can still correct for spherical aberration...so

Of course, but let's not call them 'compensated Gregorians'. You can make 
an aplanatic Gregory with 2 prolate ellipsoids, or analogs to the standard 
Cassegrain variants with conics that are easily computed using well known 
formulae. I've had a spreadsheet posted for quite a few years to help with 
the design of just about any Cassegrain variant you can think of. All of 
these are Cassegrains, and he, Gregory, and Mersenne deserve credit as the 
originators of all two mirror designs. Schwarzschild was the first to 
explore aplanatic designs involving two mirrors, followed by Couder, 
Ritchey, and Chretien.

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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