Lens coating

[Caldwell 14]

I bought a Celestron Nexstar 102 stl a few weeks back and have now had a good few nights out with it, its actually a better scope than I thought it would be for 350 quid. I have been allowing any dew to dry off inside the house before I put the leas cap back on and put it back in its case. Tonight I noticed when checking it was all dry that there appears to be a few imperfections in the coating on the outside of the lens. I only noticed when I looked down the tube into the light, should I be worried?

[rfdesigner]

Best thing is to take a pic of the 'defect' and post it.

It's probably nothing to worry about at all.. do you keep some dessicant in the box with it?

Derek

[ronin]

If you have let it dry inside then it is probably just deposits from the evaporation of the water. Water marks are common if the dew simply evaporates. The stuff in the atmosphere isn't pure water and will leave a deposit. Actually the stuff in the atmosphere is a mild acid, and the coating is likely to be Magnesium Flouride or Calcium Flouride

Although many say not to touch glass it does get dirty so it is either live with the marks or clean. Bet you clean the windows at home and on the car, and on the car it is a rubber blade the "scraps" the dirt off.

If you have something to clean it with use that, a cotton wool bud is a good instrument with something to dampen the surface. Just get the surface damp so that whatever is there is loosened and so comes off easier.

[great_bear]

I remember there's also something about Celestron coatings that can make them look a bit peculiar if looked at from a certain angle.

Best not to worry about it really - dew would not have damaged coatings on a brand-new telescope.

[Caldwell 14]

Thanks to everybody for their replies.

On closer inspection, and I do mean close, there are about half a dozen pin sized holes in the coating which appears to be on the INSIDE of the lens. You can clearly see them as white/clear through the bluish coating of the lens, The light has to be just right to see them, if a light is shone into the tube directly you can't see them at all.

What do we think?

[king-jaffethehutt]

I have had these on nearly every optical device I have owned and no real drama's caused.

camera lenses with very very fine scatches in the coatings and fluff inside expensive zoom lenses that are sealed units

Slight bubbles in surface coatings. i would imagine only the very high end stuff escapes this?