Re: ATM RE: Making a Schmidt-Cassegrain

[Bill Marriott <btk@pacbell.net>]

Roger's comments are pretty accurate, in regards to difficultly factors.
If you want to try something exotic, but easier to do, you might look at
a Maksutov, especially the Newtonian variety, the tube will be longer
than a SCT, but the Newt Mak is definitely with the realm of atmr's
You can check out my unfinished web page on my long finished MakNewt at
http://www.starlightoptical.com

Regards;

Bill Marriott

Roger Ceragioli wrote:
> 
> Hi, David.
> 
> I haven't made a Schmidt-Cassegrain, but have looked into the matter.
>  Bob Pfaff, on the other hand, who's no longer on the list (I think),
> has made a bunch of Schmidt plates and a Schmidt-Newtonian.  If you're
> serious, you might want to contact him.  My understanding is that he
> uses the vacuum pan method and there are postings concerning this in the
> archive.
> 
> But I can tell you a little about the difficulties of making a
> Schmidt-Cassegrain.  The main problem is the corrector plate, which for
> the typical  8" f2/f10 commercial telescopes requires something like 25
> microns of aspheric departure (if memory serves).  You might be able to
> do an accurate job using the vacuum pan method, but maybe not.