Introduction

Abstract

The fundamental paper by Johnson and Morgan describing the standard stars, the first cluster observations, and the properties of the UBV system was published in 1953 (Johnson & Morgan 1953). We celebrated in 1993 the 40^th anniversary of this photometric system, which became used all around the world. Although some justified criticisms were raised against the definition of the U filter or the original reduction procedure of the U - B index, the UBV photometric system contains two of the most important parameters, namely the apparent V magnitude and the B - V colour index. They are very much used, but no recent catalogue of mean values has been prepared for several years, although the number of published measurements has nearly doubled. The previous catalogue (Nicolet 1978) collected the UBV data published prior to 1976 for 53845 stars. The data collections have been continuously updated, and the latest catalogue of original data has been described by Mermilliod (1987a). He also analysed the content and produced lists of erroneous or suspect measurements (Mermilliod 1987b, 1987c).