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

[Jim Burrows <burrjaw@earthlink.net>]

At 2004-05-28 23:13 +0200, Raphaël Guinamard wrote:

>I've read in the French version of Texereau book "La construction du
>télescope d'amateur" that the general formula (for any type of curve) of the
>longetudinal aberation DeltaP is given as DP=-H2/R+H4/2R3, where H is the
>radius of the zone and R the curvature radius of the miror.
>For the parabola, the formula is given as DP= -H2/R, but without saying if
>the H4/2R3 is neglicted or if simply doesnt exist.

DP = h²/2R is exact for a parabola and moving-source.  Fixed-source is 
quite a bit more complicated - just multiplying by two is an approximation 
which is generally good enough, but not at the level we're talking about 
here.  Back in a bit after wasting some scrap paper...

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

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