Methods for identification of the digital frames and selection of reference stars on them

Abstract

Requirements for accuracy of astronomical observations continue to rise. Coordinates determination of celestial objects is performed by relative method with using of reference stars. Method of the reference stars selection and methods for determining the position of objects on digital frames determine the accuracy of astronomical observations of stars. The sets of frame measurements and stars catalog should be prepared to form the set of reference stars, that are corresponded to the investigated region of the celestial sphere. Pairs of these sets are identified by using of the following identification method: - Common task of the identification the measurements of the frame and stars in the catalog is divided into the private ones; - Preliminary selection of hypotheses of identification the measurements of frame and stars in the catalog is performed; - Intragroup identification is reduces to the assignment problem that can be solved by the Hungarian method. The purpose of the method of the reference stars selection is described below. Constants plates are formed on the base of the identification pairs of frame and catalog star measurements. They link coordinates of stars measurements in the coordinate system of the CCD frame and equatorial coordinate system. The rejection of a significant number of the identified pairs is performed after solving the problem of identification. This action is necessary to improve the accuracy parameters of estimates of the constants plates. Decisive statistic for the pairs rejection is the summary deviation between the estimates of the equatorial coordinates of identified "measurement-star" pair. Also the estimation method of the accuracy parameters of estimates of reference stars coordinates on the digital frame was developed. The obtained results confirm efficiency and reliability of the developed method. The indirect confirmation of the efficiency of developed method of the digital frames identification and reference stars selection on them is a high accuracy parameters of the positional measurements of asteroids performed with the involvement of this method. The computational method of the reference stars selection is used in the CoLiTec software for automated asteroids and comets discoveries on the series of CCD frames. Also the method of the reference stars selection provides high parameters of accuracy, as evidenced by results of the CoLiTec software.