List of highest astronomical observatories

This is a list of the highest astronomical observatories in the world, considering only ground-based observatories and ordered by elevation above mean sea level. The main list includes only permanent observatories with facilities constructed at a fixed location, followed by a supplementary list for temporary observatories such as transportable telescopes or instrument packages. For large observatories with numerous telescopes at a single location, only a single entry is included listing the main elevation of the observatory or of the highest operational instrument if that information is available.

Prior to the late 19th century, almost all astronomical observatories throughout history were located at modest elevations, often close to cities and educational institutions for the simple reason of convenience. As air pollution from industrialization and light pollution from artificial lighting increased during the Industrial Revolution, astronomers sought observatory sites in remote locations with clear and dark skies, naturally drawing them towards the mountains. The first permanent mountaintop astronomical observatory was the Lick Observatory constructed from 1876 to 1887, at the modest elevation of 1,283 m (4,209 ft) atop Mount Hamilton in California. The first high altitude observatory was constructed atop the 2,877 m (9,439 ft) Pic du Midi de Bigorre in the French Pyrenees starting in 1878, with its first telescope and dome installed in 1904. Astronomical observations were also made from Mont Blanc in the late 1800s.

A few other high altitude observatories (such as the Lowell Observatory in Arizona and Sphinx Observatory in Switzerland) were constructed through the first half of the 20th century. However, the two most important and prominent of the early 20th century observatories, Mount Wilson Observatory and Palomar Observatory, were both located on mid-elevation mountaintops of about 1,700 m (5,600 ft) in southern California. The stunning successes and discoveries made there using the world's largest telescopes, the 100-inch Hooker Telescope and 200-inch Hale Telescope, spurred the move to ever higher sites for the new generation of observatories and telescopes after World War II, along with a worldwide search for locations which had the best astronomical seeing.

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