used to confirm or rule out physical and visual systems (binaries and multiplets). Notable results were included in "A General Catalogue of Photoelectric Magnitudes and Colours in the UBV System of 3578 Galaxies, Brighter than the 16-th V Magnitude (1936-1982)" by G. Longo, Antoinette de Vaucouleurs and H.G. Corwin (1983) (see also Gérard de Vaucouleurs), with significant part of its data obtained from Belogradchik observatory. During the 1990s, beside fast stellar electro-photometry of variable stars, it was also a base for meticulous observations of minor bodies of the Solar System, including the famous Shoemaker-Levy 9 comet encounter with Jupiter in July 1994. In recent years Romanian astronomers have jointly used the observatory for an astrometry project, linked to the Gaia programme, prior to its launch in December 2013. It was by that time an automatic seismograph was mounted in an adjacent isolated compartment, where it serves both Romanian and Bulgarian seismologists. Current field of research involves CCD observations mainly of a long range of variable star types, as well as active galactic nuclei (AGN) - namely blazars. Observations are performed by researchers of several teams, as part of respective national and international scientific projects. Through the years Belogradchik Observatory saw cooperation and conducted simultaneous observations with similar facilities in Ukraine (Crimean Astrophysical Observatory), Russia (Terskol Observatory (Caucasus)), Armenia (Byurakan Observatory), Greece (Skinakas Observatory (Crete), and Chelmos Observatory (Peloponnese)), Serbia, Romania, Slovakia (Skalnaté pleso Observatory (Tatry)), Czech Republic (Ondřejov Observatory), Poland (Toruń Observatory), Germany, France, and India, among others. Simultaneous observations with Rozhen Observatory are also regularly carried out. Observational time is managed and distributed by a specialized time allocation committee of the institute. See also List of astronomical observatories :Category:Astronomical observatories by country :Category:Astronomical observatories in Bulgaria References External links Official website Institute of Astronomy website Rozhen Observatory website Alexander Tomov's history as a director (in Bulgarian) Bulgarian Academy of Sciences Astronomical observatories in Bulgaria Buildings and structures in Vidin Province Belogradchik Municipality