Computer identification of celestial objects and its problems: the case of optical identification of X-ray sources.

When a new celestial source is detected in an energy range, for example X-rays, where the total number of known sources is relatively small, attempts will be made to identify it with objects already known in other energy ranges. The authors discuss the problems that they encountered in trying to identify a number of X-ray sources, detected by the Imaging Proportional Counter of the Einstein Observatory, with catalogued extragalactic objects. The main problem is the lack of precision in the coordinates of the less recent catalogues.