The delicate metalic surface of the mirror at the heart of an astronomical telescope must be renewed periodically. When a telescope is pointed to the sky, its mirror is necessarily exposed to the elements. Oxidation and airborn particles such as dust and pollen gradually reduce the mirror's reflectivity, making the telescope less efficient.

Washing the mirror helps to restore some of the lost reflectivity, but can do only so much. Renewing the thin metalic coating requires that the mirror be removed from the telescope, the old coating carefully stripped with acid, and the glass meticulously cleaned. The mirror is then placed in a chamber under high vaccuum and a new surface applied by vaporizing metal in the chamber.

The thin layer of aluminum which coats the front surface of Lick Observatory's Shane 3-meter Reflector is replaced about every three years. The task of removing, resurfacing, and replacing the six-ton mirror, occupies a crew of more than half a dozen technicians for four to five days.

These pages record in pictures the latest realuminizing of the 3-meter mirror, begun on Monday, February 14th, 2000, and completed on Thursday the 17th.

Morning and afternoon of Monday, February 14th: Removing the Mirror (approx 1.0 Mb)
Evening of the 14th through the small hours of the morning of the 15th: Cleaning and Stripping (approx. 0.6 Mb)
Morning and afternoon of the 15th: Moving the Mirror (approx. 0.9 Mb)
Afternoon and evening of the 15th: Applying the Coating (approx 1.0 Mb)
The 16th and 17th: Reinstalling the Mirror (approx. 0.7 Mb)

The 3-meter telescope was returned to operation on the night of February 18th, one day ahead of schedule.

Last modified: Mon Feb 20 15:00:00 PST 2000 HOME
Elinor Gates