I never use compressed air in any form for optical devices - camera lenses, binoculars, eyepieces, etc. The compressed air can force dust and dirt particles into crevices and places where it shouldn't, and otherwise might not be able to go. I do use a small compressor for artwork and model painting, but I've never used it for cleaning optics or other sensitive equipment, like computers. For my 8" SCT, I commandeered one of my wife's unused (unused is important!) makeup brushes with which I very LIGHTLY sweep dust off the surface. Only when I'm confident that I've removed all of the grit, I then follow with a bit of lens cleaning solution and a lens cloth or lens tissue. I never scrub the surface but only lightly remove fingerprints or other smudges with the dampened cloth. I usually just use the same solution that I use for my eyeglasses, which I buy from Costco. I may do this once or twice a year, depending on use. I keep my brush in two Ziploc bags, one inside the other, to keep it from getting dirty. I admit to also having used the makeup brush on my Newtonian optics, but only one or twice in perhaps ten years. When I do that, I BARELY touch the surface with the brush, because I know that even the relatively soft hairs of a makeup brush or a lens brush can scratch the aluminum coating or drag particles across the surface that can also scratch. Chuck, I'm very envious of your shop and shop skills. I worked in an automotive shop for several years, and I miss the pneumatic tools. Kim -----Original Message----- From: utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com [mailto:utah-astronomy-bounces+kimharch=cut.net@mailman.xmission.com] On Behalf Of Josephine Grahn Sent: Tuesday, May 08, 2007 12:34 PM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] dirty lens We should all remember the difference between the very delicate coatings deposited onto a primary mirror, and the much tougher surfaces of eyepieces and corrector lenses. While care should always be taken, what Joe is cleaning is more akin to his eyeglasses than to the primary mirror. Blowing grit off is fine, and you never want to rub grit around on any glass surface, but for the corrector lens, there is no need to be quite so careful.