ATM DK Cass Questions II

["Bennett, Thomas D" <thomas.d.bennett@lmco.com>]

Thanks Mike, Dave and Gene for your encouraging words and Bratislav for your
frank and informed opinion. It has caused some additional thought about
proceeding with my DK Cass project. My goal was to produce a "planetary"
scope to complement my existing general purpose scope (C9.25) and could use
the same mounting (GM8). This being the case, the primary criterion for
proceeding with this project is whether I can fabricate a DK Cass that can
perform significantly better than my C9.25 for lunar/planetary observing.
Given my limited glass pushing experience and test procedures available to
me (foucault test & spherical interferometric reference), is it reasonable
to produce a fair-to-good OTA, and would such an OTA satisfy this criterion?
Bratislav mentioned encountering only 2 excellent Cass systems and many
mediocre ones produced by ATMers but not how many were in the fair-to-good
range. I think a realistic short term goal would be to produce a usable
fair-to-good OTA with a long term goal or improving it over time (by
fabricating a better secondary?) with a final goal (perhaps unattainable) of
producing an excellent system. There is a fun and experience component
involved in this project. I don't expect to produce an excellent system in
one shot but to try to evolve an excellent system as a final goal. Do you
think I can produce an OTA that will meet these expectations? 

Texeraeu's book (just got it) mentions a Method of Hindle that involve the
fabrication of a spherical test disk of focal length equal to the Cass
primary. Looks like a foucault test is performed on a double-pass beam which
strikes the secondary twice thereby increasing its sensitivity. Texaraeu
states that the characteristics of the Hindle sphere are not "stringent".
Bratislav - would this get me the sensitivity needed for an excellent
secondary?

        Thanks - Tom