[ATM] Incorrect shadows

["Cheryl and Les" <lescher@columbus.rr.com>]

Hello Group--- I have an issue that I hope someone here can help me with.
I am trying to figure an 10 inch mirror with a ROC of 122 inches.  I am
using the slitless tester shown on the Stellafane site, with a dial
micormeter to measure the movement.

In  testing the mirror the micrometer readings are fairly close to what is
called for with r2/2R.  (C= 0, 32% =.010, 60% =.040, 75% =.059, 95% = .80)
But the problem is that when I remove the couder mask the shadows don't
correspond to what the books say they should.  Specifically, starting with
the knife edge at the center zone's ROC I have the "bottom of a bowl" type
shadow but when the knife edge is at the ROC for the edge zone the shadow
matches what I think is supposed to be the 70% zone of the mirror.  If I
move the knife edge back much further e.g. .190 inches , I get the shadow
you'd expect for the edge zone. ( The half-moon )

 Am I doing something fundamentally wrong?

Thanks in advance for any help anyone can offer.

Les

_______________________________________________
ATM mailing list http://www.atmlist.net/