Extremely Large Telescope

The dome of ESO's Extremely Large Telescope on Cerro Armazones in Chile's Atacama Desert, at the 2025 topping-out ceremony that marked construction reaching its highest point, with flags fixed to the top of the frame. The numbers explain the scale of the steelwork: the main mirror will be 39 meters across, built from 798 segments, almost four times the width of Keck's. It stands at 3,046 meters, in the same desert as Paranal.