Re: [ATM] Aplanatic Gregorian (was: 25" mirror possibilities)

[Michael Lindner <mikell@optonline.net>]

On Wednesday 24 November 2004 11:08 pm, lou krajci wrote:
> ...whip up aplanatic Gregorians.  If
> nothing else...maybe we can come up with some simplifications/rules of
> thumb...some starting points and examples for ATM's to start from.

Reading Schroeder's "Astronomical Optics" (which is indeed a $100 book!) I got 
interested in the aplanatic gregorian. After running through the equations, 
however, I discovered it was difficult to come up with a practical design. 
Secondary sizes tended to be 50% or larger and/or the mirrors became quite 
aspheric. My conclusion was that this is not an easy scope to make nor a very 
useful design to build - better performance for less work out of almost any 
other 2 mirror design. I suspect that's why it's not in R&V or many other 
books.

Clear skies.
-- 
Michael Lindner
http://www.starastronomy.org *** http://home.att.net/~mikel
http://www.atmsite.org *** http://www.atmlist.net

_______________________________________________
ATM mailing list http://www.atmlist.net/