Gran Telescopio de Canarias
Visitors of the Gran Telescopio de Canarias (GTC) inside the telescope, La Palma

The Gran Telescopio de Canarias on the island of La Palma is currently the largest optical-infrared telescope in the world and one of the most advanced. The primary mirror consists of 36 hexagonal segments of 1.90 m vertices, 8 cm thick, and 470 kg, which act together as a single mirror. The GTC collecting surface is equivalent to that of a telescope with a mirror diameter of 10.4 m. The focal length is 169.9 m and therefore the maximum field of view is 20 arcmin in diameter (about the size of the full Moon).

Gran Telescopio de Canarias at sunset | Photo: Ana García,
Gran Telescopio de Canarias at sunset | Photo: Ana García,


After years in the drawing boards of the Institute of Astrophysics of the Canary Islands, in 1994 GRANTECAN SA when it was founded, with the aim of designing and building the world’s largest telescope: the Gran Telescopio Canarias. Subsequently, agreements were signed with the Government of Mexico, for two of their universities to participate in the project and also joined as a partner the United States, through the University of Florida. The telescope cost no less than 130 million euros and has an annual budget of nearly 9 million Euros.

The construction of the telescope at the Observatorio del Roque de Los Muchachos on the island of La Palma, began in 2000 and the start of the science phase began operating in March 2009. The telescope time is shared by Spanish scientists (90%), Mexico (5%) and the U.S. (5%), the same percentage who contributed to the initial project.


  • We can compare the power of sight of the telescope to four million human eyes. It could distinguish the headlights of a car at about 20,000 miles away.
  • The metal structure of the dome is assembled with screws 16,000 and 43,000 metal nuts.
  • The mirrors are cleaned with powdered snow made of carbon dioxide. There are 6 spare mirrors.
  • GTC employs about 65 people or so (about 45 on the island of La Palma alone). There are 4 working groups: maintenance, science, management and development.
  • Any day between 10-20 people are working on the telescope, the rest work in offices remotely. However, at night, despite its size, the telescope requires only 2 people to run observations: an astronomer and a technician. It’s all computerized.



The Gran Telescopio de Canarias studies the nature of black holes, star and galaxy formation of a very young Universe. A fairly booming field developed here is the study of distant exoplanets (Planetary Transits) and very energetic events such as: very distant supernovae & black hole collisions.

See scientific publications derived from the Gran Telescopio de Canarias data by clicking here.

More about the other telescopes at the Observatory Roque de Los Muchachos can be found on the official website of the Observatory or at Telescopio Nazionale Galileo and William Herschel Telescope.