Fig. 4
a Sectional machining drawing of the primary mirror with the honeycomb-shaped light-weighted structure. The marked dimensions are the geometric dimensions in actual production. b Schematic diagram of the primary mirror and the mirror cell. c 100 load spreaders are arranged at the back of the primary mirror. d Finite element analysis model of the primary mirror. e and f Gravity-induced surface deformation at the zenith and horizontal directions. g and h Surface residuals after being compensated in the zenith and horizontal directions. i The latest update on the manufacturing progress of the primary mirror at the Mirror Lab of the Steward Observatory, University of Arizona: the recently cast 6.5 m blank out of the furnace and in good condition