[ATM] Stubborn TDE

[David Steinhauer <desteinhauer@verizon.net>]

I've been trying to get rid of the TDE in my 6" f5 mirror, without success.

Here's my original Ronchi photo, before I tried tackling the TDE.  It is 
quite spherical, but has a
narrow TDE.  Note that all my Ronchigrams are outside of focus, and all 
my KE photos have the
knife edge approaching from the right.
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060521-Ronchi1-sm.JPG

First I tried using accented pressure just inside the edge, with TOT.  
All I did was increase the TDE
and create a central hill:
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060529-Ronchi-sm.JPG
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060529-KE-sm.JPG

Using Allyn Thompson's method, next I tried using short 1", narrow W 
strokes with TOT.  I did short
5 minute polishing sessions with 5 minutes of cold pressing in between.  
After quite a while I finally
managed to get it to look close to how it looked at the start.  However, 
the TDE is still there.
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060716-Ronchi-sm.JPG
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060716-KE-sm.JPG

I tried using accented pressure again, making sure I cold pressed every 
5-6 minutes.  But again the
TDE increased instead of decreased.
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060812F-Ronchi-sm.JPG

So I went back to the short 1" strokes with TOT.  This time I tried COC 
rather than a W stroke. 
Again I'm getting closer to my original photo, but it's taking a long 
time (twenty-four 5-minute
polishing sessions so far). 
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060829-Ronchi-sm.JPG
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060829-KE-sm.JPG
http://www.atmlist.net/contrib/desteinhauer-at-verizon-dot-net/060829_6inch/060829-KE2-sm.JPG

So, to summarize, my original Ronchi and KE photos look the best of 
all.  Until I started working on
the TDE, I would cold press for a while and then do long 1-hour 
polishing sessions with no cold
pressing in the middle.  I realize now that that was too long, but even 
so I still managed to get the best
figure so far.  With all of my efforts since then I've only managed to 
make it worse!  I've never been
able to see a diffraction ring all the way around - I've only seen it on 
just one side.

Any ideas on what I could be doing wrong?  How much downward pressure 
should I be applying?  I
tried doing MOT, but that also didn't get me anywhere at all. 

David Steinhauer
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