[ATM] My main testing method ..

[vorblesnak@peak.org]

I have been wanting to throw this out to the list and get some discussion
on it.

I use a very coarse ronchi grid, 50 lines to the inch, but I don't use it
the way the gurus of ronchi use it, I don't match curves.  I use the lines
to smooth the mirror, no zones, turned edge is identified, (actually I
could just tell you one was there, after all I polished the mirror),
regular curve from edge to center.  I also look at the sharpness of the
lines to gain some idea of the smoothness of the surface.

Now I pull it back to the ROC and look for that moment when the lines at
the center begin to diffuse into a gray zone, a zone of confusion.  I
concentrate on just the middle of the mirror and watch for that subtle
change.  That is line one.  Now I do the same thing to the edge of the
mirror on the vertical center where the lines are easiest to see.  That is
line two.  The distance between should be r squared over R.

This is very much like a Foucault test but I could never read the shadows
of the Foucault test well enough to figure the mirror.  I know, I know,
some of you will argue that I still can't read the shadows.  Using the
ronchi this way allows me to read alot of data from the mirror and still
get pretty close to a precision test.

So, kick it around a bit.  Peck holes in it and give me some opinions please.

David Davis
Toledo, OR 97391

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