Development of the Automatic Control System and Photon Counting Terminal of An Astrolabe at the Yunnan Observatory

A circle inductosyn and a digital indicator, the elements of the angle tester, are installed on the rotation axis of the astrolabe. The location of the automatic guiding and the position tracking of the astrolabe are controlled by a microcomputer. The tracking and location accuracies are ±4" and ±3-4", respectively. By adopting the photon counting technique, the limiting magnitude of the astrolabe increases up to the 11th magnitude from the original 7th one. The observational capability of the instrument is greatly increased and it will make greater contribution to the future star catalog compilation.