At present, only 12 of the telescope's planned 36 mirror segments are in place. The 1.9-meter hexagonal segments are slightly larger than the 36 mirror segments of the twin Keck I and II telescopes on Mauna Kea, Hawaii. As a result, the light-collecting area of the Spanish monster scope will be equivalent to that of a single 10.4-meter mirror — a 4% increase in diameter over Keck.However, since the GTC is a single instrument, it lacks the interferometric capabilities of the Keck Observatory pair or the quartet of 8.2-meter telescopes making up Europe's Very Large Telescope in Chile. (The special-design Hobby-Eberly Telescope in Texas and the similar SALT Telescope in South Africa are often listed as having mirrors 11 meters wide, but only parts of their mirrors direct light to the focus at once.)
The Gran Telescopio Canarias sits just below the rim of the Caldera de Taburiente, the steep, dormant volcano on the island of La Palma off the coast of Morocco. This is the site of Europe's Observatorio del Roque de los Muchachos, which has been expanding for several decades. The observatory is already home to the British/Dutch/Spanish 4.2-meter William Herschel Telescope, the Italian 3.6-meter Telescopio Nazionale Galileo, the MAGIC cosmic-ray telescope, and a host of smaller instruments.Construction of the GTC and its 35-meter-diameter dome cost 130 million euros and took seven years. It was hampered by planning problems, cost overruns, and the difficulty of accessing the 2,400-meter-altitude site.
Spain (to which the Canary Islands belong) is the 90% partner in the GTC Project. Three Mexican institutes are minor partners, as is the University of Florida at Gainesville, where engineers have developed a mid-infrared camera called CanariCam. Major research areas for the new telescope will be cosmology and the search for extrasolar planets.
More information is available at the GTC website.