Re: [ATM] Edge polish - when to call it good

["jamoore47" <JohnMoore47@mail2web.net>]

hi Mark!,

sounds like you did a really fine job in testing for the polish,
but like you said, being as it is going to be a beginner's mirror,
you will probably be okay, 10.5 hours is more than enough time,
for a complete polish on a 6 inch mirror, in fact, for that time,
sounds like not enough pressure was being put on the polisher,
during the polishing process, but I'm just guessing, during polishing
there should be an average, of five to 10 pounds of pressure on a 6 inch mirror,
with a medium hardness sub faceted lap.

after you finish parabolizing, use the star test for your final evaluation,
you can always go back to finish polishing the mirror, If the view is not satisfactory,
or if the star test shows a satisfactory image, you can either leave it be,
or try a new star test, and make a mask for the outer 3/8 edge of the mirror,
and test again with the mask in place and see what you come up with,

My best wishes to you and your mirror, for a final tip,
on your next mirror, use slightly shorter strokes, and the pressure of five to 10 pounds,
with a good sub faceted lap, and you're polishing sessions should go a lot faster,
also use a 60/40 approach, meaning 60% of the time, TOT, 40% of the time,
MOT. The reason for a 60/40 approached, is to ensure the polish will meet,
at the 70% zone.

Hope This Helps!, and my best wishes to you,

John Moore.
atm since 1974.
======================================================================================


-----Original Message-----
From: Mark [mailto:MarkSKowalski@comcast.net]
Sent: Sun 11/12/2006 11:25 PM
To: atm@atmlist.net
Subject: [ATM] Edge polish - when to call it good
 
I've spent probably 4 hours trying to finish the polish around the edge of a
6" f/6 mirror.  Darn last 3/8" is bugging me.  10.5 hrs spent polishing so
far.
 
With a laser, I get a little bit of reflective texture around the edge.
>From center to that last 3/8" zone there's virtually no scintillation.  The
Ronchi shows some TDE but not much. Visual inspection using a strong light
shows no grayness, no pits, no scratches, just a nice polish.  
 
I think I'm worrying too much.  That laser test is sooo sensitive.  Should I
just call it good and get on to figuring?  I'm probably going to donate the
mirror to some young Newton anyway...
 
Mark


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