Re: [ATM] Foucault test : DP=-H2/R or DP=-H2/R+H4/2R3 ??

[Jim Burrows <burrjaw@earthlink.net>]

At 2004-05-29 08:08 +0200, Raphaël Guinamard wrote:

>Jim: the second term is H4/2R3 or H4/2R2 as you wrote? It make sense to me
>that is should be homogene to m in the dimension equation.

Oops, shoulda used more scrap paper <g>, yes, it's H4/2R3.  Writing it 
pretty:  Foucault KE distance from mirror vertex f = R + 2x + 2x²/R, with x 
= parabolic mirror surface height at zone radius H = H²/2R, and fixed 
source at R.

>My miror is a 24" f/3.3. On the control paper the optician gave me it is
>written "mobile source".
>So he didn't make error. Am I Right?

Man!  A really fast 24" - quite a project!  If the optician did it 
correctly, he wouldn't use either formula because, as we said, it just 
applies to a parabola.  One should calculate the surface profile directly 
from the readings and then find the RMS deviation from the best-fit 
parabola.  If the readings (table of zone radii and corresponding KE 
positions) are on that control paper, e-mail them to me and I'll give you a 
second opinion.

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

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