RE: [ATM] Foucault/interferometry comparisons

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

Vlad,

Very interesting!  I need to look at this more, to make sure I understand where
this second term comes in.  I checked for my 18" f/4.5, and it skews the outer
zone by .005", which is very significant.  Thanks.

-- Steve Koehler
   steve_koehler@securecomputing.com

> Nice presentation. The examples do indicate that Foucault does tend to see
> mirror surface flatter than interferometry. 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. If only the main term is used, a
> perfect mirror reads as overrcorrected (i.e. the outer zonal radii measure
> progressively longer than what they are "supposed" to be). Mainly
> negligible, but can become less than that for larger fast mirrors. This is
> of course, well known, but  it may have been neglected in some cases.
> 
> Vlad


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