低纬子午环用CCD测微器观测时的星径曲率改正

本文推导了低纬子午环采用ＣＣＤ测微器观测时所得测定值的各种星径曲率改正公式。针对云南天文台具体的地理位置（纬度为２５°），在不同观测天顶距情况下，给出了ＣＣＤ视场中不同位置的天体通过参考平面（子午平面或卯酉平面）时，星过记录时刻和天顶距测定值的星径曲率改正模拟运算结果。结果表明：对于偏离ＣＣＤ芯片相对中心的天体，其星径曲率改正值比较大，且随天体偏离距离的增加而增大。

On the Problem of Curvature Correction in Case of Low Latitude Meridian Circle(LLMC) with an Attached CCD

Since the first engineering project of LLMC is almost completed in Yunnan Observatory, it is urgent to make adequate preparation for the second engineering, that is to say,the planned project of Low Latitude Meridian Circle with an attached CCD(hereafter LLMC CCD). As a part of the preparatory tasks, it is imminent to solve the problem of curvature correction under circumstances of LLMC CCD. Different kinds of curvature correction are formulated in this article. Considering the specific geographical latitude in Yunnan Observatory and various observing zenith distance, authors have presented simulated results for curvature correction of recorded time and corresponding zenith distance when various celestial bodies cross reference planes, i. e., the meridian plane or prime and vertical plane. Results indicate that the curvature correction seems to be larger than was previously expected for celestial bodies deviating from the relative centre of the CCD chip, the much more celestial bodies in question deviate, the larger the curvature correction is.