From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


The lateral spacing of the light path is o.k.  It doesn't have to be over/under.

when you get close enough to the ROC with the Ronchi grating, doesn't it
act like a foucault?  When one grating line image becomes so wide, doesn't
it appear like the foucault test image?  I think it does.  This could be
your jumping off point to come up with a modified grating, maybe a straight
edge instead of the grating. Be careful in deciding which edge you are
using and the direction of the Ke movement.

Colin


-----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")

      Hello all,
     I have some questions about Ronchi testing, and the knife edge in the
foucault test.
             I am still polishing my 3/4 x 9" mirror. I have  6.5 hours of
polish with a felt covered tool
     and CEO. I made my pitch lap last weekend using a latex mold that I
made myself. Well the
     squares came out all nice and even, and beveled. One thing that was
wrong was the face of the
mold that follows the curve was uneven in thickness, thus nice looking
squares at random elevations.
         Well you can probably predict the out come after warm pressing this
lap.... all the squares filled
in. I rechanneled and pressed til I had full contact. Any way I have now
1hr polish with the lap, which
cleaned the surface quite well.
        Now I have been doing ronchi tests wth my rig and have a mechanical
question,........
      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).
      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??
These sound like the same thing but I guess not.  I am not  going to worry
too much about the
strange ronchi shapes I am seeing until I polish some more. I can barely
see the surface with a
light source on reflection . I tried the sun test with a magnifing glass
and it didn't pass, niether did
any lenses I own , camera , etc. Although I didn't try my new binocs. Well
thats a tough test anyway.
     I am running on here thanks to all
                                             RUSS JOCOY

("atm{at}shore.net")





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