From: Mark Holm 
To: bcjawsss24{at}verizon.net, atm{at}shore.net
Reply-To: Mark Holm 


There is good cleaning advice at:
http://skyandtelescope.com/howto/scopes/article_152_1.asp

If you forget the url in the future, there is a link to it at www.atmsite.org.

Ink migration is possible.  The surface of the mirror has an oxide layer on it.
    I will refrain from going in to the chemistry of chromatography (it is an
interesting and involved subject as well as a hugely important chemical
technique), but it is possible that you have an example of thin layer
chromatography.  Black marker inks typically have a blue-purple component.
That
component may have separated and moved.  It seems a little more likely that
there has been enough extra oxidation of the surface to get the oxide layer
up to 1/4 wave thickness so that it is now acting like an interference
filter. Blue-purple would be a typical color to see.  The color you see
should depend on
the angle you look at in the case of interference and not in the case of
chromatography.

If the former explanation is true, you should be able to get the stain, as
well as the rest of the center dot, off with a soak in actetone, MEK or
perhaps mineral spirits.  If it is oxidation, solvents won't do a thing,
except remove the center dot.

Mark Holm
mdholm{at}telerama.com

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