Re: [ATM] ATM: Slit equipped and slitless testers-

["David Harbour" <stainless_steel@suddenlink.net>]

100%  in agreement with you, Jerry. Well stated.

R-101/
Davey/

----- Original Message ----- 
From: "Jerry" <wa4guu@verizon.net>
To: "'David Harbour'" <stainless_steel@suddenlink.net>; "'Mark Cowan'" 
<toolontop@yahoo.com>; <atm@atmlist.net>
Sent: Sunday, May 18, 2008 7:49 AM
Subject: RE: [ATM] ATM: Slit equipped and slitless testers-


I don't worry so much about being embarrassed by being wrong and being
parabolized. I learn more by being parabolized than by watching someone else
be parabolized.

I don't think this is true for anything other than a spherical surface. I
think "covered up completely" and "serve any useful function" is a gray
area. For aspheric mirrors the image does not have a single focal point.
Zones having shorter or longer ROC than the knife position will pass light
from the extended (slit-less) light source past the knife. Depending on the
size of the source bulb, it could be that the pupil of the eye is the only
limit to how much light is seen in zones with shorter or longer ROC's than
the one the knife is set for.

The slit serves as a limit to the brightness of those zones. That is a
useful function for the other jaw... until it is covered up completely.

Jerry





-----Original Message-----
From: David Harbour

Mark, all:


The image of the slit is reversed, so of course the knife-edge
encounters the opposite jaw first- even so, after the edge of this jaw is
covered up completely, it cannot possibly serve any useful function
whatsoever; it is not visible.



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