From: "Russell Jocoy" 
To: IAPDK{at}ADMIN.DRAKE.EDU, atm{at}shore.net
Reply-To: "Russell Jocoy" 


>From: IAPDK{at}ADMIN.DRAKE.EDU
>Reply-To: IAPDK{at}ADMIN.DRAKE.EDU
>To: atm{at}shore.net
>Subject: ATM Mirror as knife-edge
>Date: Tue, 29 Jul 2003 08:41:43 -0500 (CDT)
>
>
>To perform Foucault testing in my little project area the mirror is placed
>on a counter and the tester on a work stand about 8' away.  There is
>no room behind the stand, so to get behind the KE involves bending
>and twisting into a really uncomfortable position, not conducive to
>patient reading.  This was getting really frustrating with the latest
>figuring process (the mirror had developed a yin-yang kind of surface due
>to an uneven support), and I could just not come up with consistent
>readings with any confidence.  Can't change the room, so time to change
>the tool.
>
>I replaced the KE with a .5" wide 1" long front-surface
mirror scavenged
>from a flatbed scanner.  It has a very smooth and straight edge under
>10x magnification.  It is tilted back at 45 degrees and is viewed by
>looking straight down.  As the mirror is moved out of the light
>cone the virtual knife edge (an Air Nife?) gives an excellent view of
>the mirror.
>
>This is MUCH more comfortable, bending but no squatting or twisting.
>
>The light source is a pinhole, but it's a bit dark and only works with
>all the room lights off, so the next thing is to make a slitless version.
>Or maybe a small lens over an LED to make a bright virtual pinhole.
>
>Paul Kline
>pk6811s{at}acad.drake.edu
>



("atm{at}shore.net")

    Paul,      I put forth this idea on the net 6 months ago. It may seem
like a great idea and the image may look good but you are now testing not
only your telescope mirror but the mirror you are using to
change your veiw... It does not work well ( only for drastic changes on the
surface of your primary)
I would suggest to find a "hall" or  a room leading into a hall. 
Also think about using a room diagonally
and down from your eyepoint. My tester is at eye level and goes down to the
floor., this saves a little
space and keeps the primary leaned back to the testing stand for less
stress for a thin mirror.
       If your view mirror is of the utmost flatness , you might get by, but
let others on the list have their
say on this one...         Russ Jocoy
("atm{at}shore.net")

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