ATM Dall-Kirkham Cassegrain Questions

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

Hi Everyone,

I just joined the ATM mailing list to get some advice on a potential
telescope project. I currently have a Losmandy GM8 mounting and C9.25 OTA
system. The C9.25 is a good general purpose scope but has a large contrast
degrading 37% central obstruction. I would like to get a "killer" planetary
OTA to complement it. I'm thinking of making a 9" F40 Dall-Kirkham
Cassegrain with a F5 primary and 8X secondary. This OTA would be about 40"
long, 10" in diameter, have a central obstruction of <15%, and shouldn't be
too big for my GM8. I made a 6" mirror many years ago which seemed to work
alright but that was a F12 sphereical. My questions are:

        (1) Would a 9" F40 DK-Cass make a good planetary scope?

        (2) Is the DK-Cass a do-able project for a novice glass pusher?

        (3) Is the Foucault test (I've ordered University Optic's tester)
precise enough for me to get a good figure on the F5 primary? - I choose F5
because I read that a faster primary would be extremely difficult.

        (4) Is the 1.25" sphereical secondary going to be difficult to make?
- A friend suggested that I could just purchase a bunch of Edmund
plano-convex lenses with the proper curvature; pick the best and one and
figure it if neccessary and get it aluminized.

        (5) Is there a computer algorithm or spreadsheet available that can
assist me in designing the baffle system?

        (6) Are there any special difficulties with the DK-Cass design? - I
read that it is the easiest Cassegrain to construct because of the
sphereical secondary but the primary is a prolate ellipsoid. Where do I get
the zonal reading for this shape?

I would go with a long focal length (>F10) Newtonian but I don't think my
GM8 could carry anything bigger than a 6 incher.

                Any advice you could provide would be helpful - Thank you -
Tom Bennett