Vapor deposition of the primary mirror

In the process of repeating vapor deposition of the aluminum of the primary mirror, the old aluminum film is removed from the glass of the primary mirror, the glass surface is carefully washed, and a new reflective coating is applied. Observatory staff take this opportunity to conduct large-scale maintenance of the telescope, as this work cannot be carried out while the Subaru Telescope is in nightly use. These works take a few months in total.