Re: ATM Cassegrain as 2nd project / optics calculations

[William Mc Hale <wmchal1@umbc.edu>]

On Wed, 7 Aug 2002, Kevin McEnhill wrote:

> Is there a way to deal with the field curvature? I have been thinking of
> an RC for a large deep sky camera but keep coming to this field
> curvature thing.
>

Well there are a couple of ways to deal with field curvature.

1. You can always get a field flattener corrector; either one designed for
an SCT (if you design your Cassegrain to have the same field curvature of
and SCT) or you can make one.

2. For a photographic instrument, make the focal length of the primary
longer and the magnification provided by the secondary smaller.  While the
tube is longer, and the secondary is larger, the final result will be an
instrument with much less field curvature.

> On an almost related note, where can I find information about optical
> design from a telescope point of view? I would like to be able to
> evaluate different designs but all I can find are subjective
> descriptions like the current thread. Software would be nice, but
> without access to a Windoze machine, I am at a loss. I have been
> considering the Advanced Telescope Making Techniques by Allan Mackintosh
> but have some reservations about buying another  $25.00 shelf queen. Any
> ideas.
>

Two books that are good are Telescope Optics by Rutten and Van Venrooij
and How to Make a Telescope by Texereau.  Texereau spends quite a bit of
time discussing the different sorts of Cassegrains possible.


Bill

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