Re: ATM time estimate for polishing

[Aplanatic@aol.com]

Hi Ric:

>  Are you sure about the hyberbolic sec? Always thought the SC's had 
>  spherical sec's- easy  and cheap to make.

Yes, I am positive.  They use a proprietary method to figure the secondary 
after the primary and corrector are matched and tested as a unit.  This makes 
the "custom figured optics" quite acceptable from a performance point of view.

For a description of the compact, visual SCT consult Rutten and van Venrooij. 
 It is apparently close to the design still in use.  They give the secondary 
deformation as SC = -0.88.

I live about a mile from the Celeston factory and know several people that 
work there.  Not surprisingly, many of the Celestron folks are amateur 
astronomers.

Dave Rowe
Torrance, CA
Medium Format Astrophotography:
http://members.aol.com/aplanatic/photos/astro.html