RE:ATM DK Cass Questions II

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

Thanks for all responses,

I've located and purchased an 8" F16 Tinsley Classic Cass OTA badly in need
of repair - optics are in good shape but need recoating. I will refurb this
OTA to get an idea of what planetary performance I can expect from a Cass
with about 25% central obstruction compared to my C9.25's 37%  and how well
my GM8 will handle this load before I decide to proceed with my F40 Cass
project. The Tinsley is longer than my C9.25 but seems to be significantly
lighter but is missing some parts (focuser & finder scope). Is anyone
familiar with the quality of Tinsley optics (circa late '60s) in general or
their Cass optics in particular?

I called up Celestron to inquire about the shape of their SCT primaries for
possible use as Hindle spheres for testing Cass secondaries. They told me
the C9.25 primary was spherical but the C8 primary was parabolic! Could this
be possible - Celestron techs have given me wrong info before. They also
said they do not sell primary mirrors separate from their OTAs so trying to
locate a dropped/damaged C8 OTA or removing the corrector on my C9.25
(scary) are probably my best bets.

                - Tom