The Gemini North telescope, on a mountain-top in Hawaii, has a mirror 8.1m in diameter, six times wider than the main light-collecting surface of the Hubble.
British astronomers, who have played a pivotal role in the pounds 115m project, said the clarity of the first images had surpassed those of the Hubble. "The images are twice as good as Hubble and, to be frank, they haven't even started yet," said Paul Murdin, head of astronomy at the Particle Physics and Astronomy Research Council.
Light picked up by ground-based telescopes suffers interference as it passes through the atmosphere, so, to give ultra-clear images, Gemini North's 20-ton mirror has a coating of reflective aluminium weighing no more than an empty soft-drink can. Patrick Roche, a project scientist on Gemini and astronomer at Oxford University, said the telescope is able to resolve a point of light in the sky with an angle of one tenth of an arcsecond wide - equivalent to being able to spot a 10p coin in Oxford from a position 40 miles away in London.
A second telescope, called Gemini South, is being built on a mountain in the Atacama desert of Chile, so that astronomers can cover the southern sky.
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