Paranal Receives New Mirror

The Visible and Infrared Survey Telescope for Astronomy (VISTA) -- a 4.1-m-diameter primary mirror and a vital part of the world's newest and fastest survey telescope -- has been delivered to its new mountaintop home at the Paranal Observatory, where the telescope is being assembled at an altitude of 2518 m, in Chile's Atacama DesertCerro. VISTA will form part of ESO's Very Large Telescope facility. The mirror will be coupled with a small camera for initial testing before the main camera is installed in June; the facility is expected to begin operation early next year. "Now astronomers can really look forward to being able to perform unparalleled observing of our Southern skies," said Richard Wade, president of the ESO (European Organisation for Astronomical Research in the Southern Hemisphere) Council and chief operating officer of the UK Science and Technology Facilities Council (STFC). VISTA is the most strongly curved large mirror ever polished to such a precise and exacting surface accuracy, with deviations from a perfect surface of less than 1/3000th of the thickness of a human hair. On arrival at Cerro Paranal, it was lifted by crane into the telescope dome, where it was washed and coated with a thin layer of protected silver in the facility's coating plant. Silver is the best metal for the purpose, the ESO said, since it reflects over 98 percent of near-infrared light, better than the more commonly used aluminium. The the reflectivity produced by the silver coating -- a relatively new venture -- is well above that specified and exceeds all other telescopes to date, ESO said. VISTA is managed by the STFC's UK Astronomy Technology Centre.