Re: [ATM] Transverse Error

[Jim Burrows <burrjaw@earthlink.net>]

At 2008-01-25 13:47 -0600, Mike Lockwood wrote:

>In Foucault testing we mostly assume light is behaving like a ray
>bundle, and it works sufficiently well to make superb mirrors.
>FigureXP is used for reducing Foucault data, so I explained transverse
>error in that context.
>
>Rays are still good enough, IMO.  I get enough FFTs at my day job, and
>if I keep transverse errors very low my eyes and my clients never
>complain.

Yes, 150 years of Foucault testing have proven its worth, including 
on the Hubble primary <g>.  Where the FFT intrudes on the ATM is when 
he tries to deduce the mirror surface using a single image, e.g., 
Hartmann tests, interferometry (maybe you don't need FFT in that case 
if you've got a good reference not too far from the surface).

My objection to transverse error is it is so far from wave optics 
that you can't trust it for the "Am I done?" test.

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

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