Main Stellar Spectrograph (MSS) . ... Optical elements have been designed mainly at the Vavilov Optical State Institute, Leningrad. ... There are two Schmidt cameras with a focal length of F=600mm and F=300mm. ... In 1991 the Schmidt camera (F:2.3) was modified by the Stellar Spectroscopy Laboratory for using of new detectors (a two-dimensional photon counting system, CCD's). ... The optical layout of MSS with the Schmidt camera (F:2.3)(without its preslit devices) is presented here . ...