Re: ATM Aplanatic 4-mirror telescope system

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

At 17:52 02-12-02 +0000, kwhitefire@juno.com wrote:

>Of course, I'm always the theorist.  This is what I have:
>
>This design features 4 mirrors on-axis.  The field curvature is in excess 
>of 250 miles with excellent construction and polishing techniques.  There 
>are no exotic curves, though the primary does have a huge 
>perforation.  Field of view is .25 degrees half-angle.
>

This looks like it's not quite aplanatic, at least according to OSLO LT. 
You're on the right track though, if you're really interested in an all 
reflective astrograph.

If you want some inspiration you might check out 
<http://www.ast.cam.ac.uk/IoA/mmmt/> or 
<http://www.dmtelescope.org/design.html>.

One problem with 3 mirror designs like this (the flat doesn't count) is the 
3rd mirror is looking at the sky and unless you baffle for it you'll end up 
with two sets of images at the focal plane. Realistic designs have 50% or 
larger effective central obstructions once you baffle them properly.

Mike Peck

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