The "Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne" was founded 1950 by amateur astronomers at the Archenhold Observatory in Berlin-Treptow. The intention was - and still is - to support amateurs in the systematic observation of variable stars.
The observations are published and therefore may give professionals additional information for their work. The observation programs of the BAV are composed in cooperation with professionals in regard to their research foci.

Especially long-term observations are highly valuable and enable us to deduce the physical characteristics of variable stars. From measurements of brightness variations the times of maximum or minimum are derived. Moreover, the elements of brightness variations of specific stars are derived and new variables are systematically sought and classified.

Until the 1980s visual observations dominated. Later the light-electric photometry was established, while nowadays the CCD-technology prevails. Today more than 2,000 maxima and mimima are observed per year.

The following variable types are systematically observed: Eclipsing binaries, short-period pulsating stars (RR Lyrae, delta Scuti and delta Cephei stars), long-period pulsating stars (Mira stars, RV-Tauri and semi-regular stars), eruptive and cataclysmic stars.

The observation results are communicated in the BAV Mitteilungen. Between 1950 and 1981 these were mainly published in the Astronomische Nachrichten, since then primarily in the Information Bulletin on Variable Stars (IBVS) of the commissions 27 and 42 of the IAU. Until 2010 more than 200 BAV Mitteilungen were published with more than 43,000 observed maxima and minima.

The professionals are interested in the collaboration with amateurs as long as they can rely on high quality CCD-results which are typical for the BAV observations. At the biennial BAV conventions professionals do not only present their work, but also express wishes for support by amateurs.

Collection of more than 160,000 times of minima about 2,000 eclipsing binaries In 2004 this data collection – to honor its creator now called "Lichtenknecker- Database of the BAV" – was opened to the experts. It is available through this BAV- webpage. The BAV does not have any rights on the recorded observation results; these are still with the authors and observers. But particularly with regard to the enormous efforts we expect the citation of the official title "Lichtenknecker-Database of the BAV" whenever using its data.
The observations were collected from many worldwide available literature sources. In our understanding they are nearly complete, especially with regard to historic observations. The search covered more than 200 publications and periodicals. The criteria for including stars in the database are a brightness of more than 13 mag in normal light and a declination north of -20 degree. There is no limit for the amplitude or period.

A comprehensive description of the work of the BAV is available through one of the following links available.
english version
german version

Berlin, September 21^st, 2010; Joachim Hübscher