The Multiple Mirror Telescope operated between 1979 and 1998 with six honeycombed borosilicate mirrors by Corning, each with a diameter of 72inch, which were donated by the NRO after cancellation of the reconnaissance mission KH-10 (codename DORIAN) based on the Manned Orbiting Laboratory [REF].
With the exception of the Bolshoi Teleskop Azimutalnyi (BTA-6) and William Herschel's 40-foot telescope, major optical telescopes prior to the MMT used equatorial mounts.