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December 7, 2023


All about GTC

How will it work?

The mirrors

Telescopes are basically systems of lenses or mirrors that refract or reflect the light that reaches us from objects in the Universe. Astronomers collect this light and study it. Until a few years ago the size of mirrors limited how far we could see, but the development of large telescopes like the GTC means those limits are now being pushed back.

The primary mirror gathers light and deflects it to the secondary mirror, which in turn deflects it either to the Cassegrain focus or the tertiary mirror. From there the light is deflected to either the folded Cassegrain foci or the Nasmyth foci - we will explain what foci are a little later on.

By now it will be obvious that the mirrors we have been talking about for the GTC are no ordinary mirrors. They are a step forward in the way we use materials and technology in the pursuit of better image quality.


Each segment’s shape varies slightly, a scarcely perceptible but crucial difference that means there needs to be a way of identifying the pieces so they can be fitted perfectly into the jigsaw puzzle. This prompted GRANTECAN to give the mirrors Canarian names. Engraved on the reverse, together with a code, will be the names of the islands themselves, their national parks, birds, trees, plants and regional dances, helping identify the project even more closely with the Canary Islands.

The technical name of the ‘Folía’ mirror, for example, is OP-MI-SG-006-0001. OP stands for optical, M1 for mirror one (primary mirror), SG for ‘segment,’ 006 for ‘type six’ and 0001 to show that Folia is the first of seven segments of this type.

Main islands, from west to east:El Hierro, La Palma, La Gomera, Tenerife, Gran Canaria, Fuerteventura and Lanzarote.

National parks and reserves: Timanfaya (Lanzarote), Jandía (Fuerteventura), Tejeda (Gran Canaria), Teide (Tenerife), Garajonay (La Gomera), Taburiente (La Palma) and Frontera (El Hierro).

Trees of the islands: Almácigo - Mount Atlas mastic, Sabina, Marmolán, Sanguino, Drago - dragon tree, Aderno and Mocán.

Canarian plants: Cardón - canary island spurge, Bejeque, Tabaiba, Verode, Tajinaste, Codeso and Retama - Teide broom.

Birds of the islands: Guincho - osprey, Graja - chough, Capirote - Blackcap, Canario - canary, Alpispa  - grey wagtail, Guirre - Egyptian vulture and Pardela - little shearwater.

Regional dances: Folía, Isa, Seguidilla, Tanganillo, Sorondongo, Saltona and Vivo.