Re: ATM Cassegrain as second telescope project.

["Suzy Jackson" <suzyj@bigpond.com>]

Hi,

Many thanks for the encouragement.  I guess I can plough ahead and see what
transpires.  I can't see any great merit in going to a Ritchey-Chretien
design for this (as a first cass), as the spot diagrams (f/15 system) are
already nice and small anyway, and the R-C design drives up the eccentricity
(and I guess the difficulty) for both surfaces.

So as a first project I'll make an f/1.9ish Hindle sphere.  I'm keen on
using the Hindle sphere to test the secondary, as from my understanding it's
a null test for a hyperbolic secondary, whereas to make a hyperbolic concave
test surface would require me to do much more interpretation of the test,
not to mention leaving me with a useless piece of glass afterwards.  The
Hindle sphere on the other hand can be used for other things afterwards.

For now I'll stick with an f/4 primary, I think, though I'll keep in mind a
super fast Cassegrain for later, as a compact telescope.

Thanks heaps to everyone.

Regards,

Suzy

---
Suzy Jackson        suzyj@bigpond.com        http://www.suzyj.net
http://www.atnf.csiro.au/people/Suzy.Jackson