A direct drive mount (DDM) requires excellent ballance on both axes. There is no clutch or break on the declination and polar axis. A ring of permanent magnets produces torque against a ring of electromagnets in order to rotate and lock the axes.
Because of the complex rib geometry, the primary mirror is low mass (17 kg, - if it was monolithic it would be 50 kg). Six nylon lateral pressure pads prevent the mirror from shifting in the cell. In addition, each lateral pressure pad slides vertically on six ball bearings.
The spider with the secondary mirror removed. The three-element flat field corrector is visible in the spider’s center gives an 80 millimeter flat focal plane. The entire assembly as pictured is 13 kilograms.
If this mirror blank was on display at a museum of modern art, connoisseurs would think it was an abstract installation. More beautiful, stiffer and lighter mirror blanks do not exist. This is the primary mirror in Norway's largest optical telescope. It is made of Schott borosilicate glass, 620 mm in diameter, 73 mm thick and weighs only 17 kg. Only Dream Cellular, LLC, can produce so lightweight and stiff mirror blanks.