Re: [ATM] RE: [atm_free] The zonal Foucault test is free ofinherentcorrection bias - some supporting graphs

["vladimir sacek" <vlad@copper.net>]

Steve,

 > Nothing has turned up in the simulations--Foucault performs nearly
flawlessly. <

I'd say that it is rather Foucault simulations performing nearly flawlessly. 
Consequently, the Foucault also does but only under condition fulfilled by 
the simulation, which is that the intensity level in each of the two zonal 
openings can be precisely measured. Something our eyes can't even come close 
to during the actual test. Linfoot himself acknowledeges that, and states in 
the conclusion: "The zonal settings are most accurately determined not by 
comparing the brightness of the apertures (i.e. zonal openings) with the 
knife-edge stationary, but by observing which darkens in advance of the 
other as the knife-edge is brought across."

That brings us to a practical problem of determining at what point of either 
side of the focusing zone this becomes apparent to an average eye. And, 
alternately, at which point it ceases to be apparent and becomes to look 
like a null. It seems logical that it depends on physical  properties of the 
3-dimensional intensity distribution within focusing zone. Any significant 
asymmetry here could be a source of measurement bias.

If there is such bias, it doesn't necessarily mean that it presents an 
impassable obstacle for experienced mirror-makers. They don't need to know 
what it is, where is it coming from, or why, just that doing a specific 
slight modification to the ortodox routine - applying some sort of "fudge 
factor", or some other specific form of deviation - makes it more likely to 
come closer to a desirable result.

In any instance, before anything else is done on this subject, it should be 
positively determined if there is a clear evidence of the "alleged" bias 
and, if it is there, specify its extent.

Vlad


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