From: "Bill T." 
To: atm{at}shore.net
Reply-To: "Bill T." 


Well, whatever the design it's got to somehow increase the effective focal
length far more than the 10% or so available from Wynne-type designs.  A
~30" that maxes out the exit pupil with a miserly, uncomfortable ~16mm
eyepiece is just simply not satisfactory IMO.  But I'll definitely buy into
an f6+ 30" with a reasonable eyepiece height.  I've looked through a
25" f6 with a wide-field, high eye-relief 25mm eyepiece, and that set
a personal image standard that I've never seen beat.

I don't see that the type of figure on the primary is that big an
issue...at 30" even a good sphere requires lots of figuring.

The trick is to find a corrector scheme that is as (relatively) easy and
cheap as a Ritchey-Chretien secondary, which only makes you figure one
hard-to-test surface, rather than 4 or 6 or more.  Ok, so you have to
flatten the secondary back for testing...that's still only 2 surfaces for
the RC "corrector."

Then there's the sticky issue of supporting the RC scope high enough for a
comfortable eyepiece height.  Darn!  There's always a catch...maybe a 45
degree flat would help.

Bill T.


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