Uploaded January 2025 | Updated September 2026, 2 weeks ago

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With a 39-metre primary mirror, ESO's Extremely Large Telescope will have five mirrors in total. Two of them — M4 and M5 — will work together to cancel out atmospheric turbulence and vibrations due to wind and the telescope's mechanisms.

We are now testing the sophisticated cell that will support the M5. This mirror will have to tip and tilt 10 times per second while remaining perfectly flat and rigid – a technological challenge, as the mirror weighs 500 kg!

Discover more about ESO’s ELT at: elt.eso.org

Watch our ELT playlist here: youtube.com/playlist?list=PLSZ2Jv0bEZHy7el0mIrOMRKkhCw8pemaZ

#ELT #BiggestEyeOnTheSky

Credits: ESO
Directed by: Angelos Tsaousis
Editing: Angelos Tsaousis
Web and technical support: Gurvan Bazin and Raquel Yumi Shida
Written by: Bárbara Ferreira
Footage and photos: ESO, L. Calçada,
A. Tsaousis, M. Kornmesser, J. Porte, B. Speet
F. Kamphues, J. C. Muñoz-Mateos, Sener.
Music: Jon Kennedy – Blow keys.
Acknowledgements: Sener.