Re: [ATM] 10 inch mirror Foucault image puzzle

[Mike Lockwood <melockwo@uiuc.edu>]

Dale,

It seems like it has to be some kind of chemical attack, and the 
pattern could be due to something that was laid on top of it, patterns 
of condensation that formed on it, a residue that remained when it was 
stored, insect tracks (I liked the worm track suggestion), or some 
combination thereof.

I was once given a 5.25" long focus mirror that was in an old ATM's 
telescope.  At the bottom of the tube, on top of the mirror, we found 
a mouse skeleton.  Being about 1990 or so before I was seriously 
making mirrors, I sent it off for recoating.  When I tried to use it, 
images were horrible.

Fast forward a bit over ten years when I finally tested the mirror.  I 
saw thousands and thousands of tiny peaks and valleys over portions of 
the mirror, like the texture of a piece of coarse sandpaper, but with 
much less height variation because the surface still looked polished. 
  In the background I could see faint parabolic shadows.  Clearly the 
mouse (and who knows what else) etched the surface.  Unfortunately 
this was before I had a digital camera, and I simply refigured the mirror.

	Mike Lockwood


Vladimir Galogaza wrote:
> If fingerprints resisted cleaning they are probably etched in after
> so long time. Perhaps a bit of polishing will be needed again. This
> can be done on one of the smallest edge fingerprints just to see
> the effect. If you are allowed to do it.
> 
> But this is minor problem compared to main question about origin of
> strange features in Foucault image.

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