ATM The perfect telescope, sort of

[Bratislav Curcic <epabcc@epa.ericsson.se>]

Anthony,

I have looked into my copies of ATMJ over the weekend, and the idea of
subaperture Maksutov corrector all spherical Cassegrain looks even more
appealing.  Ralph Field has done great job in designing several
variants, all based on very fast primary. The best looking design (for
my money) is what he calls "visual", having second lens' back (which is
concave, i.e. very easy to null test) as secondary mirror. Lenses can
be cheap Crown, and having them MgF coated, loss on 6 air to glass
surfaces (double pass) will still be comparable with losses on
"ordinary" Al coated secondary. If you want flatter field, several
"photo visual" systems are also described.

Bratislav