The second GMT primary mirror segment. The GMT mirrors are cast in a rotating furnace underneath Wildcat Stadium on the University of Arizona Campus. More than 20 tons of glass is loaded into the oven atop a mold made of material similar to the heat shield tiles on the Space Shuttle. As the furnace heats and the glass begins to soften, the oven is spun at a rate of 6 rpm. As the glass flows into the mold, its upper surface takes on the shape of a parabola in response to the spinning of the furnace. The second GMT mirror has completed cooling and workers are cleaning the top surface after removal of the upper portions of the furnace.
