The Variable Star Observers Switzerland (VSOS) is a working group of the Swiss Astronomical Society. The members are engaged in the observation and the recording of the changing brightness of variable stars.


April 30, 2018:   New observation of a Close Binary Eclipsing System: Hendrik Pruijs recorded RW Tau during 3 months. Thanks to his numerous measurements, it was possible to define the Time of Minimum and the Period of RW Tau with an uncertainty of only +/- 0.00003 days. See report and measurements.
April 10, 2018:   New observation of a Close Binary Eclipsing System: Dieter Hofer recorded AM Leo and created a lightcurve.
March 3, 2018:   Meeting with Exoplanet Workshop at the Observatory Zimmerwald, considering the data reduction using the software AstroImageJ.
Invitation,  Protocol,  Script part A,  B,  C,  D
Jan. 21, 2018:   Practical for planning: A new "Time of Minimum" calculator is available. Knowing the epoch and the period of a variable star, the excel sheet calculates the times of the 30 coming minmium phases, starting from any date.
Jan. 15, 2018:   Announcement: Workshop for Observation of Exoplanets. As announced recently, the team around the Sonnenturm in Uecht has already achieved some great success and made the results available to an international headquarter. The point now is to intensify and consolidate our previous observations. That's why we meet us to the Exoplanet Workshop at Zimmerwald Observatory. For more information, please consult the Invitation.
Dec. 21, 2017:   Great success: Anna Friedli, already known for her observations of exoplanets, submitted her graduation diploma work with the title "Ferne Welten - Transitbeobachtungen von Exoplaneten". The excellent work was graded with an award and laudation. Congratulations!
Dec. 17, 2017:   New observation of a Close Binary Eclipsing System: Hendrik Pruijs recorded X Tri and created a lightcurve. Ulrich Grebien wrote the corresponding datasheet.
Oct. 17, 2017:   A new issue of the BAV-Journal was published. Editor: Lienhard Pagel.
Oct. 16, 2017:   Again: The station SON (Sonnenturm: Thomas Friedli, Anna Friedli and Patrick Enderli) confirmed an exoplanet! During a 127-minute observation campaign, a planet passed the star HAT-P-23. The planet, called HAT-P-23b, caused a decrease of the brightness of the star of just 0.0169 mag, but this could certainly be proved. Congratulations!
Further observation details can be found here.
Aug. 5, 2017:   Thomas and Anna Friedli observed the exoplanets "Qatar-1 b" and "HAT-P-36 b" with the Robotic Solar Observation Telescope (roboSOT), which is installed on top of the Sonnenturm at Uecht near Niedermuhlern. For the successful recording, the transit method was applied. Congratulations!
July 24, 2017:   Ulrich Grebien developped a practical data sheet, making the planning, observation and recording of Variables more easier. Each of the sheets is made for a certain variable Star and contents general information, reference stars, finder charts, time of minimum and period calculator.
June 20, 2017:   The VSOS goes online.
May 23, 2017:   Workshop with Hendrik Pruijs about the determination of the brightness of a star, using the software AstroImageJ.
Feb. 13, 2017:   Lecture with Ulrich Grebien about Variable Stars.