[ATM] A foucault puzzle

[Dale Eason]

http://doeason.home.comcast.net/foucault_images/2_6inch_foucault.jpg

A foucault image of 6 inch mirrors with holes in the
center.  The one on the left is coated, the one on the
right is not.

The one on the right is supposed to be a F2.5 sphere
for a MAK.  It was made many years ago and was in
storage for many years.  It is not mine.  I find two
things interesting.  One is the surface ripple.  It
might have slowly etched from the wrapping paper it
was stored in.  I don't know.

The most puzzling thing is that the pattern continues
where the hole is.  I included the left image to show
that it is not the fault of the camera or lens but
happens with the right hand mirror but not the other.

Both the back and front of the sphere have been
polished to a transparent finish.  You can see through
it just like a lens.  I don't know if that has
anything to do with it.  First it was on a bare wood
test stand. Then in this image I tried putting a black
foam piece behind it and that was no different than
the bare wood test stand.

Have any of you experienced something like this with
blanks with a hole in them?  I have seen only these
two so I have little experience.

Dale Eason

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