Cerro Paranal - the exceptional site for the VLT (1991)

Cerro Paranal is a 2,635-m high mountain, about 120 km south of the town of Antofagasta and 12 km inland from the Pacific Coast. It is situated in the middle of the Chilean Atacama desert, in what is believed to be the driest area on Earth. The geographical coordinates are 24^o 40' S, 70^o 25' W.

ESO had been searching for the best possible site for its new super telescope already since 1983. The Paranal mountain early became one of the candidate sites. The mountain and the surrounding area was donated to ESO by the Chilean Government in 1988 on the condition that ESO would indeed build the VLT Observatory there.

Following 8 years of extensive site testing and based on the excellent reports about the astronomical conditions at Paranal, the ESO Council decided to install the VLT at Paranal in December 1990. Indeed, this exceptional site offers up to 350 clear nights a year with unusually stable atmospheric conditions. Test observations have shown that, 15% of the time, local atmospheric turbulence spreads light from a star over an angle of less than 0.45 arcsec, allowing extremely sharp images to be obtained. Moreover, there is very little water vapour in the air over Paranal, greatly increasing the atmospheric transparency at infrared wavelengths. It is generally recognized as being the best, known site for an astronomical observatory in the southern hemisphere.

The construction work at Paranal began in 1991.