From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Scott:
Pinstick is my favorite.  Ronchi will also help to show a sharper slope
change (wave in the line) in that area just to get a feel for where it
really is.  Monochromatic light with the ronchi can vividly sharpen the
lines.

If it's just the tiniest zone just inside the edge, you might use a
rouge-charged thumb tangentially.  I've had mixed success with this, (it
works, but easy to overdo it).  Somewhere there's a photo of Mogey using
his finger to take down a zone on some large optic.

I use a very slow spindle, like 2-4 rpm, and use my right index finger as a
guide on the side of the mirror to set where the ball of my right thumb
rides.  Short tangential strokes, maybe 60-80 per minute with pressure get
distributed all the way around as the mirror turns.  If you can feel the
edge of the mirror under your thumb, then you're too close.  Moderate
pressure and three turns around should be good for a start.  This warms the
zone considerably, so make sure the mirror really cools before you judge
progress.  Shifting the thumb slightly after each rotation helps to
distribute the action.

Similarly, the edge of a larger lap worked TOT around just inside the edge
and with accented pressure from your thumb will work well too.  Just make
sure the edge of the lap is irregular (press a zigzag shape with foil or
carve) so you don't dig a sharp groove.

Soft pitch helps here, as there's no danger of turning the edge.  The lap
never really travels over it, and the rest of the lap has so little
pressure, it fairly floats over the surface and has almost no effect on the
inner zones.

These methods need careful application, and it's essential to keep thinking
about how you will spread the action evenly.


Colin
The Red Thumb Brotherhood.

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of Scott
Berfield
Sent: Monday, June 09, 2003 2:38 AM To: atm{at}shore.net
Subject: ATM how to approach the current situation




Hi guys,

Making some progress on the 12", but need some advice for how to
proceed. This URL is a set of screen dumps from Figure45. I am a little
suspicious of the edge readings since I have a great deal of trouble
reading the 6th zone on the mask due to diffraction and having to look at
the two opposite zones in alternation. Thinking about trying a pinstick or
something like it to help. It looks to me like I need to work the narrow
zone just inside the edge as the primary target. The Berry book talks about
using a small lap in tangential strokes to work narrow zones. Any pointers
on doing this or on other approaches that might work?

Thanks in advance.

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Don't worry about people stealing your ideas. If your ideas are any good,
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