Re:ATM !! HELP!!! FIGURING HELP POLISHING!!!

[Dan Chaffee <dchaffee@gvi.net>]

Michael,

>A single foucault shadowgram is essentially useless!! 

I'm not so sure; having made a number of mirrors with f/#s above
f/7, I'm convinced that overcorrection can be seen at once
with just a cursory look in mirrors slower than that--in this
case, a 10" f/8 I believe. Having said that, I realize that
a foucault shadowgram may be exaggerating the contrast to
some extent, but actually, he had a number of shadowgrams
laid out in progression on his web page. It was upon those images
which I based my apparantly invisible suggestions that I posted 
immediately after his request.

Naturally, I do agree that measurements need to be taken at some point
(better sooner than later:-), especially when presenting the situation 
to the List, and particularily in the case of a beginner where he/she 
has no frame of reference for the real-life experience of evaluating 
shadows.  Personally, if I saw on one of my F/8ish mirrors what he 
recorded, I wouldn't even bother to measure; just return to a sphere 
with a hardish, full sized  lap, TOT with slow, light 1/3-1/2 strokes 
and narrow 'W' sideswing. Anyway, FWIW that's what my experience 
attempted to bring to this unfortunate soap-operatic episode.

Dan Chaffee
Kansas City