In 1982, Ohara supplied E6 Low Expansion Glass to The University of Arizona for  the first spin cast trial mirror, used in The Vatican Advanced Technology Telescope. Over the decades, Ohara’s E6 has been used in the Smithsonian Astrophysical Observatory, the Large Binocular Telescope, and the Multiple Mirror Telescope Conversion, to name a few. Currently, E6 Low Expansion Glass is being used to make the primary mirrors for the Giant Magellan Telescope (GMT)! The GMT is under construction at the Las Campanas Observatory in Chile. This segmented mirror telescope will utilize seven monolithic lightweight mirrors (the largest in the world): 6 off-axis 8.4 meter (27 ft.) in diameter mirror segments surrounding 1 single on-axis mirror segment, forming a single optical surface 24.5 meters (80 ft.) in diameter. 

The 8.4-meter lightweight honeycomb GMT mirror segments are being produced at the Richard F. Caris Mirror Lab at the University of Arizona. Ohara E6 glass is placed inside a giant rotating oven where it is “spin cast,” giving the glass a natural parabolic shape. Each of the 8.4-meter diameter primary mirror segments weighs approximately 19 tons. 

Watch the videos below to learn about OHARA’s and the U of A’s production processes.