The Theoretic Basis of Astrometric Positioning Using Photographs with Small View-Field

Nowadays, photoelectric devices (for example, CCD camerae) have been widely used in Astronomical Photography, but they have met considerable difficulty in Astrometry. Although they can take a picture of a much fainter celestial body than ordinary astronomical plate does during much shorter time, they have too small sight-field. So it is very difficult to photo a candidate body and several position-compared stars in one picture.In this paper, the character of small view-field is employed. Based on the mathematic concept "differential", the relational formulas of the spherical coordinates and the standard coordinates are simplified. Finally, a programme, how to conjunct some-small view-field pictures for calculating the position of a candidate body, is suggested. With this method it is not necessary to exchange devices during observations, and the transition calculation from a wide view-field plate to a small view-field picture is omited. This method is quite suitable to position very faint celestial bodies conveniently and immediately.