Re: ATM Why One Pound Ellipticals?

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

Jim, remember that the secondary is part of the optical system of the scope
and thus it too has support problems.  What's worse is that the secondaries
are not supported anywhere near as well as the primary is!  Most are either
supported around the edges (with a pressure point holding them in place in
the center!) or with a big blob of glue in the middle.  What this means is
that the glass really needs to handle it's bending all by itself with no
help from the mounting system.  As a result, you don't hang 20:1 ratio
pieces of glass up there at the top otherwise you will be getting
abberations from the secondary that will mess up your views as the glass
bends due to gravity.
If you wish, you can make a large radius paraboloid and stress it in place
to a flat if you so desire but that's a lot of work for very little weight
loss.
Bob May
http://nav.to/bobmay
bobmay@nethere.com