Installation of Multiple Mirror Telescope, by Chacon, Vicki, 1978, Smithsonian Archives - History Div, One of the six cells, designed to hold the 72-inch mirrors of the Multiple Mirror Telescope (MMT), is lowered into place at the Smithsonian Astrophysical Observatory, located on top of Mt. Hopkins, Arizona. The MMT is some 8,500 feet above the Santa Cruz Valley..