Re: [ATM] Schiefspiegler!!! - (really a question about lens curves)

[Adam Perkins <scopeguru@yahoo.com>]

Gary / all,

The idea was to sacrifice aperture for the benefit of
a more forgiving primary convergence.

My hope is to find some point where the gentle
convergence of the rising primary f# will allow some
latitude in the selection of the secondary curvature.

At some small aperture, the resolving ability of the
system will be smaller than the defects of my casual
design parameters.  It just remains to be seen if I
can reatain a usable aperture, I don't really see the
point of proving my concept right with a 1/2" aperture
primary.

My proposal of using a ready-made lens as a convex
mirror element is not original, I saw it in a Sky and
Telescope article maybe 10 years ago.  The author had
built a cassegrain with a tiny secondary based on this
idea (as I remember it).  I can't recall much about
the 8" design, other than it seemed to be a special
case of a Classical Cassegrain.  His lens may have not
been a doublet...  Anybody remember where I might find
the article again?  

I hope all this made sense, I was typing with a swarm
of small children running amok next to me in my living
room :)

Adam




--- Gary Fuchs <gary@gfphoto.com> wrote:

> Adam,
> 
> After humbling consultation with my son and a bit of
> reading I realized 
> you're idea of scaling down ought to work. I'll
> think more next 
> time...or try anyway...
> 
> Gary Fuchs
> 
> 
> 
> Gary Fuchs wrote:
> > As to the Schief questions, that's an interesting
> idea. Kutter's 
> > design call for a 127" radius and if you mask down
> a 42.5" focal 
> > length mirror I think you're still going to have a
> 42.5" focal length 
> > mirror, just smaller and with a higher f ratio.
> >



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