My first Magazine Sky & Telescope - 03.2019

Telescope Care I’ve never had quite the courage to do that, but I believe he’s right. I have cleaned mirrors with Glass Plus and Kleenex without harm- ing them. But there’s a tried-and- true method that’s safer, and it’s easy enough that it should be your standard method, too. First, remove the mirror from its cell if possible. If you can’t, then you’ll have to clean it in the cell, as I’ve done in the illustrations here. Next, blow off any dust that you can. Don’t use a high-pressure air jet; just puff away whatever is loose. Get a couple dozen cotton balls ready. You’ll want to be able to pick them up one at a time with wet hands. Have some distilled or deionized water ready, too. Take off your rings. Trim your ﬁ ngernails. Seriously. Prepare a bowl of warm, soapy water. Add just a couple drops of Dawn, Ivory, or some other gentle dish soap. Unscented is best (fewer additives), but that’s not critical. Wash your hands ﬁ rst to get most of the oils off, then soak the ﬁ nger- tips of your dominant hand for a few minutes in the mirror-washing water. This will soften up your skin and get it squeaky clean. Next, rinse the mirror under warm running water. From this point on, don’t let any water dry on the mirror. Tap water leaves mineral deposits when it dries, and Mirror COATING SERVICES Here’s a list of com- panies that currently provide aluminization services for amateurs in North America. 38 t FIRST BATH Top: Flooding the mirror with warm tap water will remove a lot of the dirt. Middle: Gently swipe a soapy wet cotton ball across the mirror. Use a fresh cotton ball for each pass to avoid scraping grit particles across the mirror again and again. Bottom: Use your soapy, softened fi ngertips to feel for any remain- ing grit particles. those are hard to get off. Rinse off all the dirt you can. Use your sink sprayer if it has one. You might even soak the mirror for a while if you have stubborn spots. Once you’ve gotten off every- thing you can with running water, start in with the cotton balls. Take a single cotton ball, dip it in the soapy water, and, starting at the top of the mirror, wipe it gently across the mirror in one steady, light swipe from one edge to the other. Now throw that cotton ball away. If the cotton picked up any grit, you don’t want to be scraping it across the surface on your next pass. Work your way down with over- lapping horizontal motions, using one cotton ball per swipe. (Yes, if you’re careful you can rotate the cotton ball and get a second clean swipe out of it.) When you’ve done the entire mirror, rotate it 90° and do it again. Now take a deep breath and touch the mirror with your ﬁ n- gertips. (This is why you trimmed your ﬁ ngernails — you just want the ﬂ eshy parts of your ﬁ ngers to Aluminum Coating 807 Rutherdale Ave., San Carlos, CA 94070 650-868-5035 alcoat.net Evaporated Metal Films 239 Cherry St., Ithaca, NY 14850 800-456–7070 dynasil.com H. L. Clausing, Inc. 8038 N. Monticello Ave., Skokie, IL 60076 847-676-0330 clausing.com Evaporated Coatings Inc. 2365 Maryland Rd., Willow Grove, PA 19090 215-659-3080 evaporatedcoatings.com Galaxy Optics P.O. Box 2045, Buena Vista, CO 81211 719-395-8242 galaxyoptics.com North American Coating Laboratories 9450 Pineneedle Dr., Mentor, OH 44060 866-216-6225; nacl.com M A RCH 2 019 • SK Y & TELESCOPE

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