From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 




Typically the primary is steeply curved, like f/2-f/3, which is not a
trivial matter.  The figuring needs to be hyperbolic by about 10% or so.
This means the numbers used in the foucault or other tests need to be
increased slightly, not a big problem in itself.

The secondary is a convex hyperboloid, steeper than the regular Cass.  If
you're making a hyperboloid anyway, it's a matter of careful measurement
and figuring to get the right one.

I hear the RC is more critical to collimate, and the field is more strongly
curved than the equivalent Cass.

The other replies re: small chip size makes sense.  the difference in the
coma, astigmatism and curvature won't matter much in the central 10 mm
field on most cass designs.

I never made one, so this is wiseacreing on my part.

Colin



-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Rob
Sent: Tuesday, February 25, 2003 11:53 PM To: atm{at}shore.net
Subject: ATM Ritchey-Chretien telescopes



Hello all,

I'm new to the list. Hopefuly I won't get flamed for this..I have looked
around and can find very little info on Ritchey-Chretien telescopes in
general. I have found enough info to know that I want one :)

I'm thinking about trying to grind the optics myself. And hence my
questions. I know that the surface of a Ritchey-Chretien is hyperbolic
instead of parabolic. What I'm curious about is, how much harder is a
hyperbolic surface to grind and test compared to a parabolic surface? Is it
only slightly harder? Or is it sveral orders of magnitude harder? In what
ways does the process differ (ie same tools for testing and such?). Has
anyone here even attemped this before?

I really want to build one of these scopes and then do some
astrophotography with it..I'm thinking I might try the first one with a
6" or 8" primary, just in case things don't work out well. BTW It
has been a while but I do have some previous experience grinding a 6"
mirror with my father (when i was about 15 or 16 hehe). So I'm not totaly
new, but I'm probably just a bit rusty hehe....

So what do you guys think?? Is this possible or just a pipe dream?

Rob

--- BBBS/NT v4.00 MP