天体测量技术及应用研究组知识库

According to the requirement of the Lower Latitude Meridian Circle (LLMC) that the instrument can still determine absolutely the position of a celestial body after a scientific CCD is attached to it, a new control plan is presented in this paper. The plan includes two parts. One is that the CCD camera is driven to track the stellar image in the horizontal direction when observed in the meridian direction. The other is that the CCD camera still moves in the horizontal, while the tube of the instrument moves in the vertical direction when observed in the prime vertical direction. In order to accomplish the plan we have developed a control system that includes three main parts: a personal computer (PC), a single chip microcontroller system for CCD driving scan and a vertical angle control system. The first two parts are described in the paper. The PC sends all kinds of instructions and data to the microcontroller via an output interface board. The control software in the PC is written in C++, and the one in the microcontroller is written in ASM. Two simplified program flow charts are presented. We also discuss the CCD tracking error caused by the control system, and propose a corresponding way to solve the problem.