Determining the Absolute Parameters of the Meridian Circle by Observing the Prime Vertical (Ⅳ) Curvature Correction of the Recording Times in the Prime Vertical Direction

In this paper, the expression of the curvature correction of the recording times in the prime vertical direction is derived by means of the method of the solution for spherical triangle in combination with the plane projection of the field of view. By taking the given values of the latitude and one-sided collimation error, for example, the correction is calculated. When a zenith distance is smaller and a star is observed by rotating the axis of a meridian circle, this kind of correction is several hundred times greater than that of the Danjon astrolabe. Since the expression of the correction for the high order terms can be derived by this method according to the requirements, the method, as a way for derivation, can meet the needs of the derivation of the correction of different quantities. The check formula is also given in this paper.