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.