Re: ATM Cassegrain as second telescope project.

["Bob May" <bobmay@nethere.com>]

A Hindle Sphere is just that, a sphere.  Spheres are a lot easier to do than
a parabola or any other shape and a F1 sphere isn't going to be hard,
especially if you make it a half inch bigger in diameter than is necessary
so that you can have a turned down edge and not have to worry about it.
You do want to have the F-Ratio to be at least half of the primary's F-Ratio
for easier testing so if you have a F4 primary, you can easily do a F2
Hindle Sphere.
FWIW, I'm working on a F1.95 primary for a Gregorian and it's a nice sphere
right now with a nice edge.  When I get done with Richard Schwartz's 9.25"
mirror (presently hyperboloid from over working on parabolizing) I'll be
getting back to that mirror.  The parabolizing is going to be fun on that
short surface as I'm going to have to change the lens in the camera when
testing it as the present lens is only seeing about 1/2 of the surface.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net