Re: [ATM] Ritchey Chretien

[Jim Burrows <burrjaw@earthlink.net>]

At 2008-01-13 16:13 -0500, Francis J. O'Reilly wrote:

>Does anyone on the list have experience with building a telescope 
>using a Ritchey Chretien design. Does anyone know anything about the 
>hyperboloidal curves needed for the design or about literature 
>relating to the design?

You can begin with good ol' Tex, p. 147, Eq. (42, 43) which gives the 
conic constants for the two surfaces.  It turns out that the two RC 
surfaces aren't quite conics; Born & Wolf gives the differential 
equations for the surfaces of an aplanatic system, and a Russian, 
Terebizh, recently published an analytic solution to those 
differential equations.  I've generated two .zip files:
         http://home.earthlink.net/~burrjaw/public/aplantic.zip 
(2001-08-27, Win32, 15.7 k)
which goes into the design of RC systems, and
         http://home.earthlink.net/~burrjaw/public/rc_atm.zip 
(2007-08-27, Win32, 85.3 k)
that has a test for RC surfaces.

You can use good ol' Foucault on the primary, but the secondary is 
hard to do.  The usual method is to make a concave mirror to the 
proper specs and use that for a contact fringe test of the convex 
secondary.  I think it's kind of hard to get ~ 10 nm accuracy that 
way, and you can't try to fudge the parameters to get a best fit to 
the "finished" primary.  I use a non-null Hindle test (I should say 
"using" - I've been fiddling with this for a LONG time).

         -- Jim Burrows
         -- http://home.earthlink.net/~burrjaw
         -- mailto:burrjaw@earthlink.net
         -- Seattle N47.4723 W122.3662 (WGS84)

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