Fundamental Astrometry - A Look Through the Past


B. M. Ševarlić




In view of the immense importance for all fields of astronomy and adjoining sciences, as well as for its application, the fundamental astrometry has striven during its very long history to continuously enhance the accuracy of the stellar positions on one hand, and to include in catalogs as many stars as possible on the other. Up till the middle of the last century one had to deal on the whole with bright stars, mainly those visible with the nacked eye, for they were used in the studies of the motion of bodies of the solar system and in the determination of the geographic coordinates. With the growing needs of the stellar astronomy, the rapid development of which took place since, a strong requirement was felt not only for ever more precise positions of these stars but for their proper motions as well. In more recent times such requirement was set out by many applied seiences, and at present by astronautics too. To achieve these ends the fundamental astrometry has steadily been creating more and more precise observational instruments, had contrived better and better observational and computing methods of elaborating catalogs, looking at the same time for new ways of more accurate determination of fundamental astronomical constants, whose accuracy is essential for that of stellar positions. In consequence the fundamental astrometry is disposing nowadays of a vast fund of stellar catalogs, which, with respect to the methods of their composition, might be classified as extbf{observational} and extbf{computed} ones. The former in their turn might be divided into extbf{absolute} and extbf{relative} (visual and photographic), and the latter into extbf{derived} and extbf{fundamental} in dependence upon whether they represent a new system or are related to some of the already existing fundamental systems. Finally, with respect to cellestial bodies whose positions or other characteristics they give, the catalogs can be classified as extbf{general}, if they comprise positions (frequently apparent magnitudes and spectral types as well as reduction constants) of the ordinary" stars, and extbf{special}, comprehending binaries, variable stars, stellar clusters, nebulae, paralaxes, radial velocities, photometric and spectrometric quantities etc. In the present brief monograph we shall try, in conformity with the above stated endeavours, to layout in a condensed form the development of instruments, accessories and observational methods of the fundamental astrometry from the most ancient times up to the present, and to give a survey of the principal stellar catalogs of the same period along with their basic characteristics and purposes.