The Amimuth Transmission of the LLMC

The structure of the amimuth transmission mechanism used in the LLMC is described in this paper.It is to fit the need of 180 degree transposition of the horizontal axis and alternate observation along the meridian and prime vertical, i.e., the instrument is transposed to fixed direction using a step motor after it is raised 13mm by the two raising and lowering motors.The reason why the instrumental amimuth direction deviates after it is transposed and the method to measure and correct this deviation by combining mechanical and astronomical means are analyzed.