From: "Russell Jocoy" 
To: frank{at}katestone.com.au
Cc: atm{at}shore.net
Reply-To: "Russell Jocoy" 


>From: "Frank Q" 
>To: "Russell Jocoy" 
>Subject: Re: ATM Ronchi and foucault questions
>Date: Wed, 7 May 2003 08:27:00 +1000
>
>Hi Russell
>
>regarding
>
>  " 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."
>
>These are the same thing, however, be wary of the corrections involved.
>If BOTH ke and slit move together, the corrections are different to when
>only
>one of either the ke or slit are stationary and the other moves.
>
>If I remember correctly (this is the dodgy bit), zone corrections are r^2/R
>if only one of ke/slit
>moves and r^2/2R if they both move. Ie one scheme gives twice the
>corrections
>and this makes measurement easier and more accurate.
>
>Anyhow, check up on it and let me know if I got it right.
>I thought you might want to be aware of this as I wouldn't be surprised if
>someone out there in ATM land applied either twice or half the required
>corrections
>to their mirrors.
>
>Cheers
>
>Frank Q
>
>
>
>
>----- Original Message -----
>From: "Russell Jocoy" 
>To: 
>Sent: Tuesday, May 06, 2003 9:25 PM
>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")
> >
> >
> >
> >
> >
> > _________________________________________________________________
> > Tired of spam? Get advanced junk mail protection with MSN 8.
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>

("atm{at}shore.net")

    Thanks to all for your informative feedback, I will be in touch, I will
keep polishing, I will keep looking at those funny little & big lines,
and looking at those funny looking moon crater objects reflecting back
from my mirror across the knife edge.  Mirror making is like life, you
never know just what will happen
next, but with a liitle control at least you have a good idea......
        thanks again to all..
                                         RUSS JOCOY
("atm{at}shore.net")

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