Astronomy and astrophysics abstracts Vols 51A and 51B, literature 1990, Part 1, edited by G. Burkhardt, U. Esser, H. Hefele, I. Heinrich, W. Hofmann, D. Krahn, V.R. Matas, L.D. Schmadel, R. Wielen and G. Zech. Published for astronomisches rechen-institut