Re: [ATM] 20" f/4 - f/23 spherical Mangin Cassegrain

[Anthony Stillman <atmer@flash.net>]

Jean,

I plugged the BK7 prescription into OSLO and toy
around with it.   The corrector is pretty insensitive
to changes in TH and ROC as well as TEM.  There is one
huge problem however.  The design has effectively no
useful field.

I also plugged in the prescription for a like sized
Pressmann-Carmichel  (Spherical primary, ridiculously
oblate ellipsoidal secondary).  This design is known
for its effectively non-existent useful field.  The
two designs were fairly comparable.  The Pressmann is
a very little better.

The sub-aperture catadioptricly corrected spherical
primary cassegrain would work for on-axis photometry.


Anthony


difficile factu
hard to do

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