I prefer my optics really clean. Lens pens can smear oily dirt on the lens, or worse, scratch the lens if there is sand on it. I only use them in the field as a last resort. At home I blow off the dust with compressed air. Then I use lens tissue (available from Edmund Optics: http://www.edmundoptics.com/onlineca...=1954&search=1
) and isopropyl alcohol (aka, 100% rubbing alcohol from the local pharmacy). I fold the tissue into a tight wad no more than a half inch square and hold one edge with a pair of tweezers. I put a couple drops of alcohol on the opposite edge and wipe the lens in a circular pattern as though the tissue were a squeegee. You may have to do that two or three times, using fresh tissue each time. Do that when the lens gets really dirty and the lens pen will last longer.