Re: [ATM] Fixing Tom's oblate sphere

[Mike Lockwood <melockwo@uiuc.edu>]

Tom,

As for your link problem, I am finding the easiest way to view your 
photos is just to go to

   http://www.atmlist.net/contrib/tpolk-at-decatur-al-dot-gov/

and then navigate the folders you have set up.

> Thanks for all the help. Looks like I'm headed in the right direction. 

Yes, there is some progress, but it should be faster.  I think we're 
still missing something.

Questions:
What is your stroke speed?  (How many per minute?)
How often do you have to re-channel your lap?
Does the pitch lap feel like it's glued to the surface, or like it's 
skidding on top of the polishing slurry?
Does the friction change during polishing sessions?
Does it feel different right after a cold press?

> This has given me a new respect for the Ronchi test, which I placed
> behind the Foucault test. Still trying to fully visualize the glass
> surface in my head when looking at the Ronchi. I wish I had the
> mathematical skills to pursue it further (or to know it's not possible),
> but it seems something along the lines of David Rowes' Fringe XP could
> be developed for the Ronchi. Instead of points, lines widths would
> critical valves as they changed from outside to inside ROC.

Foucault, used by a practiced hand, will readily give quantitative 
data about the mirror's surface.  That is more difficult with ronchi. 
  Foucault is also more precise, in my opinion, especially when you 
have curved ronchi lines later in figuring.

	Mike Lockwood

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