Ministerio de Ciencia, Innovación y Universidades Gobierno de Canarias Universidad de La Laguna CSIC Centro de Excelencia Severo Ochoa

Sky Quality

Astronomical Sky Quality

Why the Canaries?The astronomical quality of an observatory is largely measured by the clarity of the sky and the number of usable observing hours per year. These factors are heavily influenced by the climate and geography of the area.

The Canary Islands benefit from exceptional astronomical quality as a result of the following features:

  • They are near to the equator yet out of the reach of tropical storms. The whole of the Northern Celestial Hemisphere and part of the Southern can be observed from them.
  • The Observatories are located 2,400 m above sea level, on top of the temperature inversion layer produced by the trade winds. This ensures that the installations are always above the so-called "sea of clouds" where the atmosphere, stabilised by the ocean, is clean and turbulence-free.

The predominant trade winds and the cold sea current that bathes the islands are together responsible for the pleasant climate and the troposphere being divided into two distinct layers through temperature inversion. 

Underneath the "sea of clouds" the turbulent motion of the lower layers of the atmosphere predominates. The "sea of clouds" acts like a lid, keeping out atmospheric, particle and light pollution. In the upper layer, where the OT and ORM are sited, the predominant winds are dry and turbulence-free and the atmosphere is extremely clear with very low cirrus (high cloud) frequency.   

Further information: Sky Quality Group Website (Site testing)

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