Determination of Zero Point for the Celestial Reference Frame(I)-Analysis of Objects Observed and the Observational Method

The importance Of determination of the zero point for the fundamental reference frame and the observational method used are described in this paper. The Newcom's method used the motions of inner planets to derive the equinox and equator, however the observations in the day time are usually subject to sources of systematic and random errors, which are four times to ones in the night observation. For the object that has the apparent area, the irregularity of the surface edge causes the error of its position. By comparison, the minnor planet is considered as most appropriate object. However in the past due to the observation error, the zero points determined by observing the minnor planets had large difference. we anaylze the reason and propose a new mothed in which we will use the low latitude merdian circle to determine the positions of asteriods. It is shown that the accuracy of the position will be reached to ±0.03.