Telescope ELT - Artist's view. - 3 - dimensional model of the European Extremely Large...

Telescope ELT - Artist's view. - 3 - dimensional model of the European Extremely Large Telescope - Artist's view of the ELT (Extremely Large Telescope), a telescope project measuring 42 metres in diameter. Construction of this European project could start in 2010, with a planned inauguration around 2017. Its main mirror will consist of 906 hexagonal mirrors assembled together, and its total surface will be equal to that of a football field. With a 42 - m diameter primary mirror, the present baseline, its total rotating mass is 5500 tons. The two platforms on each side of the structure hold large instruments. The telescope features a novel, innovative design, based on 5 mirrors. The primary 42 - m mirror is composed of 906 segments, each 1.45 m wide, while the secondary mirror is as large as 6 m in diameter. A tertiary mirror, 4.2 m in diameter, relays the light to the adaptive optics system, composed of two mirrors: a 2.5 - m mirror supported by 5000 or more actuators so as to be able to distort its own shape a thousand times per second, and one 2.7 m in diameter that allows for the final image corrections. This five mirror approach results in an exceptional image quality, with no significant aberrations in the field of view