How Do You Clean a Very Large Telescope Mirror? Very Carefully (Video)

If you ever wondered how scientists clean giant telescopes on Earth, wonder no more. This video from the European Southern Observatory shows just what it's like to clean and recoat one of the 8.2-meter main mirrors of observatory's Very Large Telescope in Chile's Atacama Desert.

"Every night the huge mirrors are exposed to the atmosphere whilst uncovered during observing sessions," ESO officials said in a video description. "They gradually accumulate dust and other pollutants that reduce their reflectivity, making them less effective at capturing faint light from the cosmos. So they are regularly removed from the telescope, taken down the mountain to the recoating facility, cleaned and finally recoated with a thin and highly reflective new aluminium layer." [These Are the Biggest Telescopes on Earth]

The mirror-cleaning process takes eight days and includes removing the mirror from its telescope and transferring it to a recoating plant. While it may look like a relatively relaxed process in this video, it's actually a tense operation, ESO officials explained. 

The Very Large Telescope is one of several observatories operated in Chile's Atacama Desert by ESO.

Editor's note: senior producer Steve Spaleta contributed to this report.

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Tariq Malik

Tariq is the Editor-in-Chief of and joined the team in 2001, first as an intern and staff writer, and later as an editor. He covers human spaceflight, exploration and space science, as well as skywatching and entertainment. He became's Managing Editor in 2009 and Editor-in-Chief in 2019. Before joining, Tariq was a staff reporter for The Los Angeles Times covering education and city beats in La Habra, Fullerton and Huntington Beach. In October 2022, Tariq received the Harry Kolcum Award for excellence in space reporting from the National Space Club Florida Committee. He is also an Eagle Scout (yes, he has the Space Exploration merit badge) and went to Space Camp four times as a kid and a fifth time as an adult. He has journalism degrees from the University of Southern California and New York University. You can find Tariq at and as the co-host to the This Week In Space podcast with space historian Rod Pyle on the TWiT network. To see his latest project, you can follow Tariq on Twitter @tariqjmalik.