The Extremely Large Telescope’ss 80-meter-tall dome takes shape in the Atacama Desert. (Image credit: ESO/G. Vecchia)
The European Southern Observatory has released a new view of the Extremely Large Telescope (ELT), as its colossal outer dome nears completion at Cerro Armazones in Chile’s Atacama Desert.
What is it?
Captured in December 2025, the newly released photo (it came out on Feb. 11) reveals how construction is progressing on the ELT’s 80-meter-tall (260-foot) protective dome, which will one day host a 39-m (128-ft) concave primary mirror four times larger than those employed by its predecessors.
The photo gives us an imposing view of the ELT’s massive motorized doors, which are in the process of receiving their outer aluminium cladding. Once in place, the outer skin will help protect the optics from the intense heat of the day while limiting night-time cooling. Shock absorbers built into the base of the structure, meanwhile, will be tasked with safeguarding the telescope from the threat posed by earthquake tremors.
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When complete, the entire upper section of the colossal dome will rotate on the concrete “pier” below, allowing the telescope within unfettered access to the pristine dark skies above, while protecting the delicate instrumentation inside from the extreme desert environment beyond.
When will it be ready?
The dome is scheduled to be complete sometime in 2027, soon after which the five enormous mirrors tasked with collecting and directing the light from the deep universe are expected to be installed in their new home.
Astronomers are hoping to make their first test observations with the ELT — a milestone referred to as “first light” — in early 2029, with the initial scientific observations expected in December the following year.
The ELT is expected to represent a significant leap forward in ground-based optical and infrared astronomy, granting scientists the sharpest views of distant cosmic objects ever attained, seeking out unknown Earth-like exoplanets and generally expanding our understanding of the cosmos.
Check out our explainer article to discover more facts about the world’s largest telescope!