The Determination of the Parameters of the Amimuth Pointing Detection System

An amimuth pointing detection system is setted in the LLMC (Lower Latitude Meridian Circle)for the detection of the instrumental amimuth pointing deviation after every transposition. The structure of this detection system and the way to determine various kinds of parameter in the system are described. It is made up of a piece of cubic reflection mirror in the centre of the instrument and an amimuth collimator. There is alway sone reflection surface of the cubic reflection mirror facing the amimuth collimator after every transposition between the meridian and prime vertical, thus forming one self-collimation optical system. The parameters needed to be determined are :the included angle between the four reflection surfaces of the cubic reflection mirror, the installation deviation of the cubic reflection mirror, the included ang le between the instrumental meridian plane and the prime plane, the scale of the Reticon on the focal plane of the amimuth collimator.