Cleaning the Ritchie Mirror
Greg Bajuk
If you observed the heavens through the “big” telescope over the last six months you might have noticed that the main 27.5 inch mirror was covered with dust, dirt and debris. Insect remains and spider webs had collected in the mirror housing. During the winter moisture condensed in the mirror housing and on the mirror despite the presence of a heat lamp at the base of the telescope—the mirror was covered with moisture spots. All of these problems degraded the telescope image.On April 2nd a mirror cleaning team assembled at the observatory to remedy the problem. Malcolm Saunders led the effort with help from Doug Tanaka, Russ Heglund, Greg Bajuk, and David Browning.
Before removing the cover that protects the mirror, the team cleaned the external parts of the telescope which included the eyepiece ring, ring support struts, and the external mirror housing. We placed plastic covering under the telescope and over the computer desk area to catch cleaning fluid and to protect the sensitive telescope control electronics, and then lowered the telescope to the near horizontal position pointing north so that we could reach the mirror.
The basic cleaning procedure consisted of gently feather-dusting the mirror housing and then handvacuuming the housing and areas around the mirror with a crevice tool. We wiped down the mirror housing area with a moist cloth, and sprayed de-mineralized water on the mirror. The velocity of the water helped to remove the loose dust and debris and also softened the remaining dirt. Then we liberally sprayed a water/ alcohol mixture over the mirror to help loosen more dirt and any oil residue. (One person stood by to relieve the cleaning person in case of excessive alcohol fumes.) Then we hand-cleaned the entire mirror using sterile cotton balls. We gently rolled each cotton ball down the mirror to remove dirt. Rolling the cotton minimized scratching. We used even more water, alcohol and cotton on stubborn areas. Finally, we daubed up residual moisture drops with cotton until the mirror was completely dry.
We documented the entire procedure with still and video cameras, and placed a written procedure with pictures in our telescope procedures book. The video documentation on DVD is available for member review and for the benefit of those members who clean the mirror in the future.
A dramatically improved mirror!