More than 100 astronomers, physicists and engineers throughout the country are celebrating a major milestone – a 51,900-lb mirror blank that is a perfect fit for a Large Synoptic Survey Telescope (LSST) being built in Cerro Pachón, Chile. The mirror blank consists of an outer 27.5-ft-diameter primary mirror and an inner 16.5-ft third mirror cast in one mold. According to the team, it’s the first time a combined primary and tertiary mirror has been produced on such a large scale. Members of the team building the LSST, a large survey telescope being built in Northern Chile, gather to celebrate the successful casting of the telescope's 27.5-foot-diameter mirror blank. (Photo: Howard Lester/LSST Corp.) The LSST requires three large mirrors to give crisp images over a record large field of view. The two largest of these mirrors are concentric and fit neatly onto a single mirror blank. The single-piece primary and tertiary mirror blank emerged from the oven at the University of Arizona's Steward Observatory Mirror Lab in Tucson, Ariz., where team members gathered to celebrate. In January, LSST announced receipt of two major gifts -- $20 million from the Charles Simonyi Fund for Arts and Sciences, and $10 million from Bill Gates. These gifts are being used to enable the construction of LSST's three large mirrors. The finished mirror is scheduled to be delivered in 2012.The LSST will be the widest, fastest, deepest eye of the new digital age when it begins science operations from Cerro Pachón, Chile, in 2015. It will provide time-lapse digital imaging across the entire available night sky every three days, mapping the structure of our dynamic universe and exploring the nature of dark matter and dark energy. The LSST research and development effort is funded in part by the National Science Foundation under Scientific Program Order No. 9 (AST-0551161) and Scientific Program Order No. 1 (AST-0244680) through Cooperative Agreement AST-0132798. Additional funding comes from private donations, and in-kind support at Department of Energy laboratories and other LSSTC institutional members.In 2003, the LSST Corp. was formed as a nonprofit Arizona corporation with headquarters in Tucson. Membership has since expanded to 25 members, including a number of national laboratories, observatories, universities, research institutes, and Google Inc. For more information, visit: www.lsst.org