Thirty Meter Telescope stats


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; 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

Mirror Segments:

E-ELT 698

TMT: 492

Collecting Area:

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

2 replies
  1. Guenther Hasinger
    Guenther Hasinger says:

    One other important factor in this comparison is the fact that Maunakea has arguably the best “seeing”, i.e. image quality of those telescope sites. The stars twinkle due to the atmospheric turbulence. Because of the way Madame Pele has shaped the Hawaiian shield volcanoes and because they are isolated in the middle of the Pacific, the air turbulence over Maunakea is minimal – on some good nights the stars do almost not twinkle at all. Thus the special power of Maunakea helps the somewhat smaller TMT to be as powerful (or even more powerful) than the big scopes in Chile. In addition, Maunakea covers the northern hemisphere with many important objects not visible from the South (e.g. the Anromeda Nebula).

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *