From: "Jerry" 
To: "'Russell Jocoy'" ,
        
Reply-To: "Jerry" 




-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net] On Behalf Of Russell
Jocoy
Sent: Tuesday, May 06, 2003 7:25 AM To: atm{at}shore.net
Subject: ATM Ronchi and foucault questions


("atm{at}shore.net")




      My ronchi screens have the light slit shining through the left side of

the screen and returning to
veiw on the right side . Is it necessary to have the light on top and to
veiw on the bottom??
I am getting nice images(although they are not spherical).


        I don't understand the setup so I will just describe my setup. In my
case I have a moving source with a slit and I replace the knife with a
grating. The returning beam is the only one going through the grating.



      My next question is on the foucault test. I would like to use the same

rig for my knife edge test
and do some rigging. This question may be dumb but in the foucault test the
knife edge  is stationary
and the light source moves?  Or  the knife edge moves and the light source
is stationary??


        It doesn't matter which is stationary. Just remember that the
movement will be twice the movement as with a tester on which both knife
and light source move together, such as a slitless tester.



It doesn't hurt to take a moment and look at the mirror with a Ronchi or
Foucault test every now and then. But don't worry about what you see until
you have polished completely. In other words... don't start figuring until
it is fully polished. It is fun to look at it now and then, but don't let
it slow you down in getting the job done. I don't know how the felt polish
thing works but with a pitch lap it would probably take me 12 hours to
polish that 9" by hand. I've seen some take longer and some take less.
My daughter fully polished out a 6" in 6 hours. I guess it is one of
those things that when it is done it is done. I track the time when
polishing but I don't dwell on thinking of the job in terms of time.

Jerry

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