From: "Richard F.L.R. Snashall" 
To: ATM List 
Reply-To: "Richard F.L.R. Snashall" 




waldo kitty wrote:
 >

 >
 > 1. Introduction
 >
 > The quick and time-honored answer to the ATM's question, "How good is
 > good enough?" is the Rayleigh Criterion: the max minus min (or "peak
 > minus valley", P-V) wavefront error cannot exceed ¬ wave. However, it
 > has been noted that there are good ¬-wave mirrors and poor ¬-wave
 > mirrors, so work on a mirror is often continued until the wavefront P-V
 > is significantly and perhaps unnecessarily less than ¬ wave. Two
 > criteria, solidly based on wave optics, are introduced here which
 > provide a more precise answer: the Root Mean Square (RMS) error and the
 > Strehl Ratio. It is shown that these criteria can be found by reduction
 > of data from the usual amateur procedures, the Foucault, classic
 > caustic, and the "poor-man's" caustic tests. Their use
could reduce the
 > amount of effort required to produce a satisfactory mirror.
 >


Has anyone here considered the possibility of using something a stronger
than Strehl ratio?  I'm thinking about something like the expected value of
the error from the centroid, given intensity squared as the weighting
function; or something like that.

        Rick S.

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