Re: ATM Cassegrainian? Advice needed

["James W. Burrows" <burrjaw@halcyon.com>]

On Fri, 6 Jun 1997, Diego Protas wrote:

> I would like to know if it is possible to build a 12.5 in. f.6 
> Cassegranian scope. I really would like to be able to do it. I know that 
> there's a problem with comma and field curvature, is this fizable with a 
> Schmidt plate? Any advice will be appreciated,

It's possible, but _hard_.  Texereau says, p. 144, "Values of (gamma) less
than 3 are not advised in Cassegrainians intended primarily for visual
use."  So this means you're talking about a 12.5" f/2 primary, a _major_
challenge (if it's a classical cass).  See Texereau for further Cass
advice.

     -- Jim Burrows:     (206)244-2933, fax -0294
     -- E-mail:     burrjaw@halcyon.com
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