Re: [ATM] Diffraction Assisted Figure Test

[Jim Burrows <burrjaw@earthlink.net>]

At 2007-03-04 20:50 +0100, Arjan te Marvelde wrote:

>I just came (again) across this page on Bob Mays' website and was wondering
>whether anybody had actually tried this test. At first glance it looks quite
>elegant, but surely there must be a caveat in it?
>
>Link: http://bobmay.astronomy.net/DAFTtest/dafttest.htm
>
>Instead of using the wires to obtain the spikes, square holes with 45deg
>mutual orientation  may be as effective as wires?

The caveat is to work with diffraction you have to use the Fourier 
transform.  I've got a couple of "Hartmann" test reduction programs, 1D:
         http://home.earthlink.net/~burrjaw/public/hart.zip 
(Win32, 2001-12-31, 508 k)
and 2D:
         http://home.earthlink.net/~burrjaw/public/hart2d.zip 
(Win32, 2006-02-02, 1.14 M)

Both programs use the image from a web cam with the lens taken off, 
and the 2D version uses, as Arjan suggests, a "checkerboard" 
mask.  I've been using (too long <grumble>) a version of the 2D 
program to figure an RC cass secondary using a Hindle sphere.

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


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