In a long awaited announcement, America’s largest optical telescope project unveiled the chosen site for its new observatory. After a long and extensive campaign of site testing and comparison, and, more importantly perhaps, much politicking, the Thirty Meter Telescope board have reached an agreement to build their telescope on the Mauna Kea in Hawaii.

The TMT, a collaboration of US, Canadian and Japanese institutes, is one of three projects in the so-called class of extremely large telescopes, or ELTs. In the last year, two potenial sites were studied in a final run-off: the well known Hawaiian mountain Mauna Kea, and Cerro Armazones, an as yet undeveloped site in the Chilean Andes. As both sites are excellent from the astroclimatological perspective, it is rumoured that the Japanese involvement was at least partly responsible for the final choice. All three of the partner countries already have telescopes and infastructure on Mauna Kea.

With the smallest of the ELTs, the 24-m
Giant Magellan Telescope confirmed to be sited at Las Campanas, also in Chile, and ESO’s strong ties with the country, TMT will ensure that an ELT will also be watching the Northern skies. In addition seems sensible to question the sanity of locating three of the world’s most powerful telescopes in a relatively small area – and one with substantial seismic activity at that.

All eyes are now on ESO, whose 42-m ELT project, the imaginatively named European ELT, is the last in the trio to be found a home. While ESO are running an extensive testing campaign at 5 sites around the world, there is much speculation that TMT’s second-choice site, Armazones, could now be in the running for the E-ELT. An announcement from ESO is expected in the next year.