Re: ATM Classical Cass

[Aplanatic@aol.com]

Tony Cecce wrote:

>  Also, I am tentatively looking at using both scopes at equivalent
>  magnification of 100x on a target of a slide of Saturn at about 1-2
>  arcminutes image size.
>  
>  The problem we are having is coming up with a 10" classical cass optical
>  set.  I have proposed using a 10" standard mirror with a flat secondary at
>  the cass focus.  But they still want to investigate a classical cass
because
>  they feel visitors should be able to see the curvature in the secondary.
>  Also, the central obstruction would probably be an issue since I would
block
>  over 25% of the light with a >50% obstruction. Their push back was "How bad
>  would the image be using a SCT optics set with no corrector plate?".

Plain horrible.  I scaled Rutten and van Venrooij SCT model to 10" and removed
the corrector plate.  Image at best focus is 2mm in diameter corresponding to
an angular diameter of 2.7 arc minutes.

The only recourse, as I see it, is to start with a parabolic or spherical
mirror and start figuring that secondary.  Sorry.

Dave Rowe
Torrance, CA