MAIN OPTICAL SYSTEM OF CHINA’S 2.16-m TELESCOPE

This paper introduces configuration of the main optical system of China’s 2.16-m telescope and the results of its optical design. There are three foci in this telescope: the Cassegrain, the coude and the prime foci. Ritchey-Chretien (R-C) system is used as the Cassegrain system. The 2-lens and 3-lens correctors are prepared for the Cassegrain and the prime foci respectively. The most significant characteristic of this optical system is that the coude and Cassegrain systems share one secondary mirror. A relay mirror is added to the coude system. When the two systems exchange, the secondary mirror moves slightly, and the coude system obtained is free from both spherical aberration and coma simultaneously. Some other coude configurations and a special configuration for setting the focal reducer are also introduced in this paper.