The best stargazing spot on Earth may be a ridge in Antarctica
Astronomers hunting for perfect skies look for darkness, dryness, height and endless clear nights. A 2009 study concluded that the place offering all of these with the least atmospheric disturbance is Ridge A, deep in the interior of East Antarctica, far from any city and almost as far from comfort.
An observatory is simply a place built for watching something, whether volcanoes, weather, the oceans or the sky, though many people reserve the word for astronomy. Early versions could be as basic as a wall-mounted instrument for measuring angles between stars, or monuments like Stonehenge, whose layout lines up with certain celestial events. Today astronomical observatories sit on the ground, fly aboard aircraft, orbit in space or even hide underground.
For optical telescopes, location is everything. Light pollution drives them away from cities, and thin, dry mountain air reduces the turbulence that makes stars shimmer, which astronomers call poor seeing. Favoured regions include the American Southwest, Hawaii, the Canary Islands and the Andes. Since the mid-20th century observatories have climbed above 4,000 metres. Mauna Kea, near the top of a 4,205-metre Hawaiian volcano, is the best known. Bolivia's Chacaltaya held the altitude record from the 1940s until 2009, when it was overtaken by a University of Tokyo telescope perched at 5,640 metres in Chile's Atacama Desert.
Most optical instruments live under domes with a roof slit that opens at night, and the whole upper dome can usually rotate to aim at different parts of the sky. Radio telescopes, built since 1933, generally go without domes. They also flee populated areas, but for a different reason: interference from radio, television and radar. Unlike optical sites, they can sit in valleys, where surrounding hills add shielding.
As research institutions, observatories go back more than a millennium. An observatory operated in Baghdad by 825, and in 1420 the ruler Ulugh Beg built a celebrated one at Samarqand. Tycho Brahe's Uraniborg followed in 1580 on an island then Danish and now Swedish, and England's Royal Greenwich Observatory was founded in 1675.
Source: Observatory
