This is an oddball question... I recently bought an Orion 150mm Mak-Cass that I have mentioned in some recent threads in the forums. Last night was the first when the temperature in our area dropped appreciably while I was observing (went down to the low 50's from close to 70 during the day). Things were getting close to dewing up and I noticed a sheen of moisture on the OTA. When I picked up the tube to get back in, I noticed a fairly large fingerprint-like smudge on the corrector plate - it was visible when I shined by phone flashlight by chance on the front of the telescope while wrapping things up for the day. I was puzzled since I am really careful about not taking my mitts anywhere near the glass in optics and take pains to handle the scope only on the metal parts on the outside - I am close to 100% certain it wasn't me. The odd thing is that smudge is basically gone this AM after the scope has been indoors and warmed up to the 70s.
Looks like the cooling down and the moisture build up made the print visible. I was curious whether anyone has seen fingerprint marks left behind on the inside of the corrector plate during the assembly process? There seem to be some threads alluding to something like this, but nothing definitive. I didn't want to try cleaning the outside of the corrector plate since I'm always afraid that I will do more damage by pressing and dragging a piece of grit inadvertently on the optics, especially if it is on the inside which would make the effort futile.
Any ideas or experience with something like this?
[I didn't take a picture with a phone last night, unfortunately... so can't post any]