From: "Tom Krajci" 
To: 
Reply-To: "Tom Krajci" 


From: kwhitefire{at}juno.com

>Wire test according to Kevin, Seeker of the Darkness:
>(I may be wrong, but it seems to work)

>Substitute a wire (I use a hair) for the knife edge.  Use a couder
screen.  >Numbers as with a Focault test.

There is no absolute need for the couder screen if you use a pinstick. For
the Foucalt test the screen helps identify where you should look on the
mirror.  A pin stick will do the same job for the wire test, and is easier
to fabricate...especially if you want to experiment with measuring more or
fewer zones on the mirror.  (If you test many zones on the mirror with the
wire test...you may want to use some way to identify/highlight which pin
you are making the measurement for...perhaps a penlight or laser pointer
shining on the pinstick just below the pin on which you are interested in
taking zonal measurements.)

Once you do the wire test, then put a knife edge back in place, and check
your overall smoothness by nulling all the zones, and check to see if you
have a diffraction ring all 'round the mirror.  Then put a ronchi grating
in place and look at the overall figure and evidence of turned edge.

Tom Krajci
Tashkent, Uzbekistan

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