(Wfoley2) wrote in message ...
Canned air might be OK for cleaning crap out of a keyboard or smoke alarm. It
is NOT a good idea for optics. There are lens brushes for this purpose. If
canned air will blow it off, then a brush will brush it off. Be sure the brush
is clean and without oils on it.
Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

I often use canned air to clean optics. The cautions about using it
slowly and only when the can is warm are true as otherwise it will
leave residue. Generally, if used at very slow rate, the impact
velocity of most dust should not be a problem.
I hand polish metal x-ray optics and use it to remove distilled water
from the mirror surfaces because no matter how pure the water, it
always leaves residue if allowed to form spots. Often, we use pure
gold surfaces and the gold is so soft that any brush will scratch it
so that is why we use the canned air.
Glass surfaces and the layer of Aluminum oxide on a telescope mirror
is probably harder than most of my optics so I do not expect canned
air to cause any pits or scratches.