ATM Interval Figuring, was 19th Nervous Breakdown

["Bill T." <twentiethwave@hotmail.com>]

Grand Ol' Frank Ward wrote...
>Try http://www.mindspring.com/~thewards/Figuring.htm

Good article, Frank.

I usually use the "intervals" method myself.  If you know what the intervals 
between Foucault micrometer readings should be you don't have to use the 
Foucault reduction software until late in the game.  I especially applaud 
your "whole surface" approach to figuring.

There was some suggestion that we should throw the Foucault test out the 
window when trying for mirrors above ~1/4 wave, and rely only on the star 
test.  Even if we don't believe the P/V from the crunched Foucault numbers, 
examining the Foucault intervals still provides an accurate way to tell if 
we are adding or reducing correction in relation to before, and whether the 
overall correction is distributed evenly across the surface.

Although the distribution of correction can be inferred from the star test 
on a perfect night, the Foucault intervals provide a more consistently 
available test.  I use the star test all the time, but I rely on the 
Foucault intervals to keep the surface sorted out evenly.


Bill T.


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