RE: [ATM] Foucault/interferometry comparisons

["Koehler, Steve" <Steve_Koehler@securecomputing.com>]

Vlad,

> One thing that may be worth
> checking out is whether the zonal readings are obtained with the use of
> both
> terms for the longitudinal radius displacement (i.e. h^2/2R + h^4/4R^3 for
> moving source), or only the main term.

It looks like there is no second term for a moving source tester.  From Jim
Burrows' Mirror Math, the differential equation for a moving source is x' =
y/(f-x), where y is the radial distance on the mirror, x is the sagitta at y,
and f is the longitudinal position of the zone null.  Taking x = y^2/(2*r) for a
paraboloid, this boils down to f = r+x, which only has the y^2/(2*R) term.

It looks like a fixed source tester has the correction term, but its effect is
probably half of what I wrote, before.

-- Steve Koehler
   steve_koehler@securecomputing.com

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