Re: [ATM] Bench star test

[Jim Burrows <burrjaw@earthlink.net>]

At 2007-06-01 23:15 -0700, Dale Eason wrote:

>I tried what is for me a new way to star test and then
>compared it to my simulated star test from
>interferometry data.  The mirror is an 8 inch with ROC
>of 119 inches.
>
>The bench star test was done at ROC using a red laser
>diode with the lens removed to make a point source
>light.  The detector was a Philips web cam with the
>lens removed.
>
>http://home.comcast.net/~doeason/interferometer/star_bench_igram.jpg
>
>The red image is the laser and web cam.  The black and
>white image is the simulated version from
>interferometry data.
>
>I think the laser point source and web cam show
>promise.

I tried to reduce such images to find the mirror surface using the 
Misell iteration which was used to find the Hubble primary deviations 
up in space when NASA stupidly chucked it up without even an 
amateur's Foucault test which would have told them it was a chunk of 
junk.  Anyway, the bench test Misell wouldn't converge.  My solution 
was to put a mask on the mirror, and then the Misell would converge 
if you restricted the iteration to only change the slopes of the 
mirror surface visible through the mask holes - this became my 2D 
webcam Hartmann test.

My guess is that in the Hubble case, they had to restrict the 
iterations to only give a smooth surface - at least the Hubble 
primary had that property.  I wanted the bench test to find higher 
order aberrations without having to model them directly.

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


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