The Thirty Meter Telescope has recently been publicized as being the largest optical telescope on earth—most recently in a Honolulu Star-Advertiser that called it the “world’s largest telescope” without even adding the “optical” classifier—which clearly erroneous; even the TMT is dwarfed by the 305 meter dish of the Arecibo radio telescope in Puerto Rice, for instance.
But if the TMT is ever the world’s largest optical telescope, it won’t be for long. The European Extremely Large Telescope (EELT) recently got the green light for construction, and the E-ELT’s official Web sight says it is slated for “first light”—the moment that it begins making observations—in 2024, within two years of the TMT’s projected first light. Other astronomy sights give other estimates; space.com projects that the TMT will begin full operations between 2025 and 2030
A point by point comparison:
Primary Mirror Diameter:
E-ELT: 39 meters129 feet
EMT: 30 meters
E-ELT: 978 square meters
TMT: 655 square meters
TMT: Mauna Kea, Hawaii, Northern Hemisphere.
E-ELT: Cerro Amazones, Atacama Desert. Chile, Southern Hemisphere.
— Alan McNarie