Cleaning and Aluminizing the Hale Telescope Mirror

This is a fascinating time-lapse video (with narration) that shows the process of the cleaning and aluminizing of the Hale Telescope mirror, which is located at the Palomar Observatory. The mirror is first removed from the telescope and moved to the area inside the observatory where it will be cleaned. Near the end of the cleaning process, the old coat of aluminum is removed from the mirror, allowing one to see the honeycomb structure of the underside. When the mirror is ready, a new coat of aluminum is evaporated onto the glass.