GMT mirror casting at UA
GMT2: Nearly 1700 unique hexagonally shaped alumina-silicate fiber refractory cores are installed to form the 8.4 meter diameter oven mold for this second mirror casting for the Giant Magellan Telescope (GMT). Randy Lutz, manager of the Mirror Lab casting team, installs each of the cores individually in a precisely determined location and distribution within the oven tub walls. The core installation, metrology, inspection, and cleaning procedures take the team about six weeks to complete. Hexagonal shaped refractory caps bonded to the tops of the cores form the base on which the borosilicate glass chunks will be loaded. During the oven firing and spinning cycle, the molten glass will flow accross the surface formed by the core tops and down into the spaces between the cores, forming the curved paraboloid upper faceplate and the honeycomb like supporting structure for the interior "ribs" of the mirror.