A team of opticians has completed a one-piece, 27-ft-diameter mirror that soon will be incorporated into the Subaru Telescope, which is under construction at the summit of Mauna Kea in Hawaii. Led by Scott Smith of Contraves Brashear Systems of Wampum, Pa., the group removed more than 9 tons of material from the original 33-ton piece of glass. The glass features a mean residual surface error of less than 0.0000005 and has a thickness of 8 in. Delivered to Hawaii in September, the mirror will be supported by 261 computer-controlled actuators, used to prevent wind and gravity from distorting it. The mirror is to be assembled in the telescope in January 1999.