[ATM] Foucault

["David Williams" <dwilliams1128@earthlink.net>]

Hello list

To do the foucault test: what do I do first.  I've turned the light on, now do I center the light between the knife and the light house?  My house is stationary.  Next I see the image of the mirror iluminated evenly overal, and when I move the knife to the left from the right the light dissappears at once..  This means that the knive is at the Radius of Curvature--- Right?  But what zone is at the radius of curvature?  Is it the whole thing?  Or just one part?  

Next,  I've heard that I need to use a mask with 6 parts hins Sixtests;  but the foucault tester I have is so sensitive that I haven't gotten used to it yet.  Does any one have advice on this?  

Also I understand how to use a micrometer, but I wonder what it's used for (to measure what compared to the R of C).  The spindle is 0 zero when it is out and the knife is even with the light house.  Then as you move the knife back from the house and lengthen the R of C the spindle contracts and is closer to 9.  

My friend Jerry Martensen who made a few scopes before, racked the micrometer all the way to the 9 position toward you to start making readings.  This didn't make sense to me.
  
Also I don't understand PLOP.

Maybe someone can enlighten me on that.
Thanks
David
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