Re: [ATM] On Axis Foucault

[Jim Burrows <burrjaw@earthlink.net>]

At 2005-06-14 18:15 -0400, Dave wrote:

>The SA from a cube splitter is very significant for an f/2 system.  Just 
>ray trace to find out.

I've used a cube beam splitter to test a 10"f/1 Hindle sphere.  You can do 
the ray tracing during the test by constructing a beam splitter correction:

         (N²(y²+s²) - y²)(s - s' + t)² = s²t²

with zone radius y, index of refraction N, beam splitter size t, true 
normal intersection s, observed normal intersection s'.  Exercise for the 
reader:  find a good-enough approximation.  (CAUTION:  dragged that formula 
out of my notes, 2879 days old.)

The way to run the test is to put the source (point or slit) on one side of 
the cube, somehow frost the observation side, and merge the returns from 
the two zones (assuming Ritchey single zone mask) using a microscope 
focussed on the cube side - FPF (Focal Point Foucault).

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

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