[ATM] Incorrect foucault readings

[Dale Eason <atmpob@yahoo.com>]

In the last few days there was a post asking for
advice as to why his foucault readings did not match
the shadows.  He listed his reading for the mirror. 
In particular the edge zone was at .8 I think.  He
used a Stellefane tester and the mirror was something
like an 6 inch F6.

I am surprised that the mirror makers on the list did
not pay attention to the .8 reading for the edge zone.
 Something is definitly wrong here.  There is no way
that should be that large.  In fact I think it should
have been closer to .04.  For a moving source tester
the edge zone foucault reading should be very close to
the sagitta of the mirror I think.

I may have remembered the edge reading wrong but it
was still way too large.

I have deleted the message and can not find it
anymore.  Perhaps others can comment better now that I
have brought the matter up.

Dale Eason


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