European Extremely Large Telescope

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This article or section contains information about an expected future scientific facility.
It is likely to contain information of a speculative nature and the content may change as the facility approaches completion.

European Extremely Large Telescope (E-ELT)
Not yet built
Organization	ESO
Location	Probably Chile or Roque de los Muchachos at the Canary Islands
Wavelength	Optical, near infrared
Built	Planned completion: 2017
Telescope style	Reflector
Diameter	42 m
Angular resolution	0.001 to 0.6 arcseconds depending on target and instruments used
Focal length	420-840 m (f/10 - f/20)
Mounting	Alt/az
Dome	Spherical
Website	http://www.eso.org/public/astronomy/projects/e-elt.html

The European Extremely Large Telescope (E-ELT) is an extremely large telescope design proposed for the next-generation European Southern Observatory optical telescope with a mirror diameter of 42 meters. ESO is focusing on this design after a feasibility study concluded that the proposed 100 m diameter Overwhelmingly Large Telescope would cost €1.5 billion (£1 billion), and be too complex.

Current fabrication technology limits single mirrors to being roughly 8 meters in a single piece. The next-largest telescopes currently in use are the Gran Telescopio Canarias and Southern African Large Telescope, which each use hexagonal mirrors fitted together to make a mirror more than 10 meters across. The ELT would need to use a similar design. In addition, ELT would also need to use techniques to work around atmospheric distortion of incoming light, known as adaptive optics.

Project E-ELT has the aim of observing the Universe in greater detail than even the Hubble Space Telescope. A mirror of approximately 42 meters would allow the study of the atmospheres of extrasolar planets. The 5-mirror anastigmat design is estimated to cost €800 million and could be completed by 2017[1].