Spring Cleaning

The southeastern US has emerged from pollen season, so it is time for the annual optics cleaning chores. I try not to clean my telescope mirrors more than once per year. They are covered when stored, but dirt finds its way on to my optics during both storage and observing.

For years I have used a cleaning formula passed down from a professional optician (thanks Don!) Generally, I use distilled water + 91% isopropyl alcohol + a drop or two of biodegradeable detergent. I use sterile cotton to gently swab the surface from the center outward, and I rinse very thoroughly with distilled water. Last winter, I washed my 14.5" mirror and I skipped the swabbing step since the coats were new, but some haze was left behind. Lesson learned - do the gentle swabbing.

After debating the use of isopropyl in mirror cleaning with my mirror-making and telescope-building friends, I decided to track down Jeff Decker, owner of Majestic Coatings, while attending NEAF last month. I wanted to get his recommendation since he coated my 14.5" mirror. I wanted a professional opinion on the isopropyl issue.

Fortunately I found Jeff and was able to discuss cleaning at length with him. We talked about the process and materials that he used on my mirror. Jeff recommended using isopropyl wipes (see below) to gently swab the surface of the mirror. He explained that since the overcoat is silicon dioxide (quartz), the isopropyl should not damage the underlying reflective coat (aluminum). I explained that I had made mirrors for years and that seemed very aggressive, but he reassured me by offering to recoat the mirror should any damage arise.

Given the discussion with Jeff, my mirror cleaning ritual has changed a little. I still use an air bulb to blow dust off the mirror first. Next, I rinse with distilled water and then soak in distilled + a tiny amount of biodegradeable detergent. I rinse after the soak with lots of distilled water, and I blow dry with the air bulb. Finally, I swab very gently with the isopropyl wipe. The wipe I used was very saturated, so I did a final rinse with distilled water and blew off all remaining droplets of water with the air bulb. My mirror is as clean as new now (and the air bulb wore out my hand muscles!)

The isopropyl swabs recommended to me by Jeff  are Clearview wipes from CleanTex. You can find them at http://cleantex.com/old/products/presaturated/clearview.htm . If my coats begin to fail over the coming year, I'll take Jeff up on his offer to recoat. Since Majestic has been in business for years, I anticipate no problems. Instead I expect to have a clean, happy mirror.

Next time - eyepiece cleaning.