Re: [ATM] RC cass secondary and starlaps.

[Jim Burrows <burrjaw@earthlink.net>]

At 2007-11-29 09:40 +0100, Dominic-Luc Webb wrote:

>Interesting! So, this is the secondary? What tests are you using?

The primary is tested using my 2D webcam Hartmann test, which 
performed pretty well on the mirror round robin.  For testing an RC 
cass, the output is the radial surface height every mm.

For the secondary, I had already made a 10" f/1 Hindle sphere, so I 
reprogrammed the Hartmann test, the "webcam Hindle-Hartmann test", to 
work on the secondary using the Hindle sphere.  In back of the hole 
in the Hindle sphere, the source is a laser shining on a 1/8" ball 
bearing and the webcam with its lens removed.  The light goes through 
the hole, bounces off the secondary with a checkerboard mask, to the 
Hindle sphere, back to the secondary, then back to the webcam.  As 
for the primary, the output of the test is the radial height of the 
secondary surface every mm.

Finally, the two surface files are read into a program which 
minimizes the wavefront RMS vs. the Terebizh solution (thanks to Mike 
Peck for finding that) to Born and Wolf's differential equations for 
the two aplanatic surfaces.

The four tests that can be run are webcam in and out of focus with 
either centered and non-centered masks on the secondary.  The test 
that came up with the 32 nm RMS was out/non-centered.  I'll take the 
other 3 tests tonight and hope for the best.

I'll send Dominic this e-mail with a picture (forbidden on the ATM list).

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

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