Re: Optical system for Mark IV

[goffaxe@azstarnet.com (Bob & Valerie Goff)]

>There
>again, from memory, I believe a C8 primary is an F/2.2 mirror. 

No,Sir.
The primary has a roc of 32" which is f/2.0.
It is the corrector that has the appropriate correction for a Paraboloidial
primary of f/2.24 .
We must remember that C-8s are essentially Dall-Kirkham systems with a
spherical secondary.
When you guys get around to deciding on an appropriate focal length for your
systems, I will give you a quote on field flattened, filtered Schmidt
optics. I am almost finished with the tooling required to refigure,
appropriately, the correctors of all of those inexact C-14s out there that
are lurking at all of those star parties. I've never seen one as good as the
prototype of all those years ago.
It makes my heart glad to see you discuss distortions. 
How about discussing the tolerance on focal length from system to system too.
This aspect of life is interesting. One can, of course, make all of the
optics test plate fit.

Or the
>diaphragm can be a real diaphragm or any combination between taking
>just the center or just the edge. In fact if you look at the profile
>of a Schmidt lens, there is a zone, known as the Kerber zone where
>the two sides of the Schmidt lens is parallel, i.e. can be replaced
>by no lens at all at this particular zone. Usually in a classical schmidt
>telescope, this zone is at 0.866 the radius. Outside this radius,
>the lens behaves as a diverging lens bringing the focus further away,
>and inside this zone, the schmidt lens is a converging lens, bringing
>the focus inside. The shape of the lens perfectly corrects the mirror
>spherical aberration.
>If this was possible, it is possible to find used optical tubes ( even
>an old orange tube would do ) and build a kind of camera support/Spider.
>3 rods could support a cardboard diaphragm of some kind. Focus would be
>provided by the C8 focus knob. Could even use the lousy mount for slewing
>the telescope.
>Alain

I have an old C-8 corrector that I am willing to donate to your effort. But
then, I have an old striated C-10 corrector too.  Interested????

Bob