Re: ATM : What is a TDE

[Brad Davy <bdavy@fred.net>]

I thought I had a TDE, based on the Ronchi Test.  I tried everything you
mentioned, but it kept getting worse.  Everything I did just made the
center get deeper!  So I went back and read the archives some more, read
Texereau some more.  Yesterday, after trying for a week, I had an
ephiphany!

Hand Position!  I was polishing with one hand on the center of the tool
or mirror, whichever is on top, and the other hand on top of the first. 
This was causing greater localized pressure in the center.  Yesterday, I
switched to the hands on the outside edge with the tool on top, using
1/4 W strokes.  Within 40 minutes, my deep hyperboloid was again a
sphere, with no visible signs of turning on the edge.  I think many
supposed TDEs are actually just unpolished edges that have not been
blended with the rest of the curve.

Now to find that parabola!

robert allen wrote:

>         All three are curable by the same method. You must use
>         strokes that remove glass from the inside of the edge. [not
>         from edge or center] These are short strokes MOT and
>         long strokes TOT. 

Brad
bdavy@fred.net                  http://www.fred.net/bdavy