A CCD Detector Attached to the Lower Latitude Meridian Circle——(Ⅰ)The Observational Principle

In this group of 5 article, with this present, article as the first one, the observational principle, various instrument constants, the method for determining the errors and the accuracy of determining of the Lower Latitude Meridian Circle (LLMC) with a CCD detector are expounded, and the absolute accuracy of location which can be attained after a CCD detector is attached to the LLMC and the role of the construction of the highly accurate reference frame of the celestial sphere played by the LLMD with a CCD detector are systematically discussed and described. In this present article, the way to give full play to the superiority of the graound-bared observation, the observational method, the formulae for the calculation of the time and zenith distance of a star passing across the meridian circle or the prime circle arc briefly decribed and the determining accuracy of the relative position in the small-angle astrometry is also estimated. Finally, it comes to the conclusion that the requirement of the tracking accuracy of the micrometer is decreased after the CCD detector is adopted.