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Old 04-11-2009, 06:40 PM
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marki
Waiting for next electron

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Join Date: Mar 2008
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Yes but the Al coating is applied in a vacuum so oxidation will not be a major problem particularly if the protective coating was also applied before the mirror was exposed to air. My concern is simply based on the integrity of the protective coating considering their micron thickness. Mirrors that are exposed to the environment such as the case in open tube and truss frame designs have to have their mirrors recoated periodically as the Al coating some how comes in contact with oxygen (eg the coatings fail) and dulls due to oxidation and the formation of AlO3. Could it not then be possible that 2-propanol used as a cleaner might also reach the surface Al ? I imagine any scope mirror that did not have protection against oxidation would have very little usefulness beyond 48Hrs as the mirrors would dull rapidly. Just as an aside, I did a little experiment today. Freshly cut Al does indeed react with with 2-propanol but very very slowly. It took about ten minutes for the surface to visibly dull.

Mark

Last edited by marki; 04-11-2009 at 06:51 PM.
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