[ATM] 10 inch mirror Foucault image puzzle

[Vladimir Galogaza]

Dale,

>The mirror has been cleaned with optical glass cleaner
>and with alcohol. Neither have changed the appearance.

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.

Have you checked the mirror with polarized light for homogeneity?
>I'm not sure if they are on the front surface.

I was expecting experienced people to give advice how to decide on dilemma
if features are on front surface. My only idea is invasive. Grind and polish
a speck on the back to see if Foucault image of this part will change.
But there must be better ideas for sure.

Your images are excellent. They can be enlarged a lot for inspection
without pixels showing out. Is it your new camera?

Regards
Vladimir.