The Hobby-Eberly Telescope's mirror is a slightly concave honeycomb of 91 hexagonal mirrors--each a 260-pound slab of glass coated in silver. The entire telescope weighs 84 tons, all of which rotates on air gaskets that ride on a gigantic concrete ring. Even the dome is unorthodox, opening like a clam shell instead of with the traditional slot. Photograph courtesy of McDonald Observatory, The University of Texas at Austin.