Re: ATM Focault testing....problems

["A.G. Ruud" <mrsruud@hotmail.com>]

Craig and listmembers: I have found it easier to to get the Foucault tester 
aligned by moving the mirror holder instead of the light source. By removing 
the pinhole or slit in order to allow more light to reflect off of the 
mirror you can easily see the reflection on the lightsource. Then it is 
simply a matter of moving the mirror holder up and down and back and forth 
until you can see the relfected beam on the slit/pinhole. You then place the 
slit ot pinhole in front of the lightsource and do a final alignment in 
order to get the returning beam where it belongs. It is important to have 
the mirror holder and tester as closely aligned as possible before you start 
to seek the proper location. It is similar to the procedure used to 
determine the focal length by trying to get the reflected beam to as small a 
point as possible. I hope that this might be able to help you spend as 
little time as necessary setting up the Foucault Test apparatus.
Alan Ruud


>From: "Craig Gibson" <craiggib@icon.co.za>
>Reply-To: "Craig Gibson" <craiggib@icon.co.za>
>To: atm@shore.net
>Subject: ATM Focault testing....problems
>Date: Tue, 26 Sep 2000 18:03:36 +0200
>
>
>Hi all
>
>I have got to the interesting stage with my first 8" but getting really
>frustrated with this seemingly simple procedure.
>
>I put the knife/lighthouse a little further from the mirror than the
>ROC.
>I turn on the light source and start to look for the point where the
>the mirror is totally illuminated by bobbing my head all over the
>place to the amusement of the household, including my dog.It
>usually ends up being quite far away from the knife edge. At least
>now I roughly have the distance from the mirror where the knife
>edge should be.
>Do I have to fiddle with the mirror now to get the reflected light on
>the knife edge? Am I doing this all in the wrong sequence? Or does
>this type of thing usually take a little fiddling to get right?
>I presume the lightsource should be roughly at the same height as
>the centre of the mirror.
>
>My apologies for all the questions, but while the books are clear on
>the concept the practical implementation therof is a problem...for
>me anyway :)
>
>Many Thanks
>
>Craig
>

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