Extremely Large Telescope gets a roof | Space photo of the day for August 5, 2025

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The world's largest optical telescope is still under construction but is raising the roof on its progress.

A domed building is under construction in the middle of a desert, surrounded by cranes and machines and scaffolding.
A view of the Extremely Large Telescope under construction. (Image credit: ESO/CHEPOX)

In the middle of Chile's Atacama desert, there's lots of activity as construction on the Extremely Large Telescope (ELT) is still underway, with cranes helping to move pieces in place.

What is it?

Here, the world's largest optical telescope will scan the sky with a primary segmented mirror stretching 128 feet (39 meters) in diameter, roughly four times larger than any current ground-based optical telescope. The large mirror will not only allow the telescope to collect more light, but according to the ESO, the telescope will also provide images 15 times sharper than the Hubble Space Telescope.

Where is it?

The ELT is being built in Chile's Cerro Armazones, a mountaintop in the Atacama desert.

A photo showing the roof being raised on the ELT. (Image credit: ESO/CHEPOX)

Why is it amazing?

In April 2025, crews at the ELT celebrated the telescope's topping-out or roofing ceremony, as the roof was raised over the dome of the telescope. Flags from both the ESO and Chile were placed on the scaffolding over the roof.

In Chilean tradition, this ceremony is known as Tijerales, and was celebrated on April 16, 2025 with a traditional barbeque for the crew. The ceremony was also livestreamed to ESO's headquarters in Garching, Germany, bringing together an international community excited about the future of astronomy.

Want to learn more?

You can read more about the Extremely Large Telescope and other telescopes in Chile.

Kenna Hughes-Castleberry
Kenna Hughes-Castleberry

Kenna Hughes-Castleberry is the Content Manager at Space.com. Formerly, she was the Science Communicator at JILA, a physics research institute. Kenna is also a freelance science journalist. Her beats include quantum technology, AI, animal intelligence, corvids, and cephalopods.

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