 This finely figured, thin meniscus mirror, held in shape by a 156-element active optics system, regularly delivers sub-arcsecond seeing.The mirror was ground and polished into its parabolic shape at the Optical Fabrication and Engineering Facility of the College of Optical Sciences of the University of Arizona (in Tucson, Arizona).The LDT is housed in a 73-foot-tall, 62-foot-diameter metal dome located at an elevation of 7,800 feet and about 40 miles southeast of Flagstaff.