Friday’s Feature Film

Cleaning Mirror
Still from YouTube movie showing the realuminizing of the 5-meter mirror of the Hale Telescope.
Stuart Goldman
Did you know that the giant mirrors of major telescopes regularly get a fresh coating of aluminum to keep them in top working order? It's not a simple process. Technicians have to take the back end of a telescope apart, remove the enormous mirror, clean it, put it into a realuminizing tank, then put everything back together. It's a little easier for a segmented mirror like Keck, because engineers can use the smaller spare segments to take the place of ones to be refreshed.

You can watch the process thanks to a time-lapse movie on YouTube. Richard Koolish forwarded me the link to a 3½-minute-long movie showing the realuminizing process for the famed 5-meter Hale Telescope atop Palomar Mountain. (One of the first things I learned after starting at S&T 20 years ago is that the telescopes aren't on "Mount Palomar.") I suppose that I found the movie especially interesting because I've stood under the massive telescope and watched as astronomers prepared for a night's observations.

The movie's uploader, "palomarskyguy," has two other videos to watch too.

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.


This site uses Akismet to reduce spam. Learn how your comment data is processed.