An association introduces herself: The
is the central organisation of the german variable star observers.

Moreover the BAV is the section for variable star observation "Fachgruppe Veränderliche Sterne" of the Vereinigung der Sternfreunde (VdS) e.V.,
which is the german association of amateur astronomers.

In the following chapters we want to report further details about the BAV.




The BAV ("Berliner Arbeitsgemeinschaft für veränderliche Sterne" at that time) was founded in Berlin in march 1950 by amateur astronomers. In 1992 it was united with the "Arbeitskreis Veränderliche Sterne (AKV)", which had been the organization of variable star observers in the former German Democratic Republic (East Germany). Since that time the "Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne (BAV)" is an association for whole Germany. Objective of the association is to support amateurs in systematic observation of variable stars. Only long term observations have a great value and make it possible to draw astrophysical conclusions from. Therefore the purpose of the association is to publish observation results and support professional astronomers with additional information for their work. Observation programs of the BAV have been drawn up in cooperation with professional astronomers with respect to their research priorities. BAV is organized into several sections to provide a closer contact between observers in their special fields of interest.


Major fields of observations are Eclipsing binaries, RR Lyrae stars, Miras and Semiregular variables.

The aim of an observation is to get the time of maximum resp. minimum brightness of the variable.

Observing Eclipsing binaries or RR Lyrae stars you can get such a result within a couple of hours. During that period of time you should observe the star in intervals of 10 to 15 minutes. Observing Miras and other Long period variables you have to estimate the stars brightness during many weeks at every evening with a clear sky.

Mainly we observe visually and photographically using Argelanders estimation method. Another important field are CCD-observations.


Principles our work bases on can be imagined as a cycle consisting of 13 steps. It can be separated into 3 special topics:

• Meeting all the requirements amateur astronomers need for useful work. [steps (1) to (4)]:
  A major requirement of all BAV-activities is cooperation with professional astronomers. This cooperation and consultation (1) leads to BAV-observing programs including about 400 variable stars (2). To realize these programs, working material (star charts) are created and provided to the amateur (3). This way observations are possible without great expenses. More over ephemeries for the program stars are calculated (4) and published in the "BAV Circular".
• Tasks regarding the observation [(5) to (8)]:
  Observation are done chiefly to find out the time of maximum or minimum brightness. Only in case of special types of variables long term light curves are taken into consideration. Among other things the attraction comes from not knowing exactly the brightness behavior during a time interval. It can only be predicted approximately. The reasons for this are changes in periods and light curves.
• Processing of results [(9) to (13)]:
  Results are collected by the BAV (9). Basing on the old elements, time deviations (O-C) are calculated (10) and published (11). After collection of a sufficient number of results, elements can be improved (12) and published (13). These new elements make it possible to draw up better predictions and new ephemeries (4). With this the cycle has closed.

• Eclipsing binaries standard program with long term observation series of the BAV (64 stars)
• Eclipsing binaries program 82 consisting of stars without systematical observation by professional or amateur astronomers (62 stars)
• Eclipsing binaries with long periods requiring observating techniques like Miras and other Long period variables (20 stars)
• RR Lyrae stars standard program (26 stars)
• RR Lyrae stars program 90 (59 stars)
• Delta Scuti stars (27 stars)
• Cepheids for binocular observation (20 stars)
• Cepheids for telescope observation (35 stars)
• Miras und Long Period Variables with observation series partially since 1950 (71 stars)
• Semi- and irregular variables, RV Tauri stars (22 stars)
• Eruptive variables especially considering Novae (12 stars)

The BAV provides a lot of benefits to its members:

• BAV Conferences
  With a two-year period and at alternating places there is a conference of the BAV together with the general meeting. Here cooperation of members can be intensified. They can get to know not only each other but also their work and techniques. Moreover professional astronomers give reports about their work.
• BAV Sections
  The BAV is organized into sections to improve cooperation in special fields of work and to provide encouragement and consultation to the members.
  - Section for Eclipsing Binaries
  - Section for Short Period Pulsating stars
  - Section for Miras
  - Section for Semi- and Irregular Variables
  - Section for Cataclysmic and Eruptives
  - Section for Photoelectrical and CCD Observation
  - Section for Photographical Observation
  - Section for Evaluation and Publication of Observation Results
  - Section for Observating Charts
  Since mid of 1996 there are additionally persons to turn to on the topics data processing and internet.
• BAV Rundbrief
  The journal comes out three or four times a year with articles about observations and theory of variable stars.
• BAV Circular
  Ephemeries of the year for all of the BAV program stars.
• BAV Mitteilungen
  Publication of our observating results.
• BAV Schnellmitteilungen
  Can be published about suddenly appearing events e.g. Novea.

All interested people can make valuable contributions and work on a field that provides great fun. It is not necessary to use a big scope, even with a binocular you can observe a lot of variable stars.

We would like it very much to inform you in detail. Write to us. Surely there is one of our 210 members living close to your place.

At the moment (May 2010) the annual fee for membership is 21 €. Please look for the current value on this page (at the end of the page).

Address:

Munsterdamm 90
D 12169 Berlin