Extremely Large Telescope Construction Update | European Southern Observatory

Extremely Large Telescope Construction Update | European Southern Observatory

The Extremely Large Telescope’s dome, still partially uncovered and showing its steel skeleton in the beginning of this video, has mostly finished receiving its layer of protective insulated cladding, designed to protect the telescope and its instruments from the harsh desert environment, including very rare but heavy rains. When the massive doors were installed the dome reached its highest point of 80 meters in April 2025 with a topping-out ceremony that featured the raising of the European Southern Observatory and Chile flags on top of the dome. Later in the year, the dome’s doors were moved for the first time.

Meanwhile, inside the dome, the main structure of the Extremely Large Telescope (ELT), that will hold its mirrors and instruments, is progressing fast. This structure, currently weighing around 3500 tonnes, was recently rotated around its vertical axis for the first time.

This video does not capture the advances carried out off-site, such as testing the ELT’s deformable mirror, key to correct atmospheric turbulence and obtain sharp images. The construction of MICADO and METIS, the first instruments to be installed at the ELT, is also progressing well. An agreement for MOSAIC, another ELT instrument, was signed in the end of 2025. With the telescope components and instruments coming together, the ELT is well on its way to start observing the cosmos later this decade.

The ELT and its groundbreaking 39-meter main mirror will tackle major challenges in astronomy and, ultimately, help us understand our place in the Universe.

Learn more about the ELT: https://elt.eso.org

Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, extending along a narrow strip of land between the Andes Mountains and the Pacific Ocean.

Credit: ESO
Duration: 2 minutes
Release Date: July 20, 2026

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