During almost twenty years of the photometric monitoring, UBV measurements of 76 bright Be stars of all luminosity classes were secured at the Hvar Observatory. For 46 of them, the time coverage was sufficient enough to permit more detailed studies on the incidence and time scales of the light and colour variability. The results are summarized in Table 4 (click here) in which Be stars are divided into early- and late-B types. Light variations on both, long and short time scales are frequent among early Be stars, in contrast to late-type Be stars. In several known spectroscopic binaries we succeeded to demonstrate the presence of phase-locked light variations related to their binary nature (KX And, LQ And, RX Cas, V1507 Cyg, CX Dra, V360 Lac, Per, Tau).
Sudden brightenings, on a time scale of a few days, were detected for o Cas and QR Vul.
In addition, UBV measurements of 48 check stars of, mostly, early spectral types were collected in the present long-term observing project.
We dedicate this paper to the memory of our late friends and colleagues Dr. Jiřı Horn and Dr. Karel Juza who not only participated in the observations but also did enormous work on the final reduction of the Hvar data.
We thank the following people who helped to secure the observations reported in this study: Drs. J. Arsenijević, J. Grygar, P. Mayer and P. Polechová, and Messrs. D. Čikotić, J. Havelka, J. Honsa, Z. Ivanović, V. Kocourek, M. Muminović, N. Novak, M. Stupar, M. Tlamicha, J. Vacek and F. Žárský. We also acknowledge the mechanical, optical and electronic maintenance of the telescope and photometer by Dr. P. Mayer and Messrs. K. Dvo°ák, K. Havlıček, J. Honsa and J. Vacek.
We are indebted to Drs. D. Baade, J. Cuypers, J. Dachs, H. Hensberge, A.-M. Hubert and J.R. Percy for their valuable comments on the first draft of this paper. Special thanks belong to the referee, Dr. C. Sterken, for his very useful suggestions and a careful proofreading of the text. This research has made use of the Simbad database, operated at CDS, Strasbourg, France.
The whole project has been continuously supported by the Croatian Ministry of Science and Technology. Finishing of this study was supported by the internal grant No. 30303 of the Academy of Sciences of the Czech Republic to P. Harmanec.