The Stellar Occultation Timing Association Switzerland (SOTAS) is a working group of the Swiss Astronomical Society. The members are engaged in the observation and the recording of occultations of stars, caused by astronomical bodies such as asteroids, moons and planets.


December 2, 2018:   In addition to stellar data, Gaia Data Release 2 (DR2) also contains accurate astrometry and photometry of about 14000 asteroids covering 22 months of observations. From these data, the Gaia team is able to derive shape models from numerous asteroids. The great thing about this is that we will be able to combine our occultation results with all these shape models to get accurate measurements of the diameter – provided we have at least two well-timed and spaced chords to fit to the shape model.
October 27, 2018:   The first meeting of the working group SOTAS was held in the Liceo cantonale in Bellinzona. Totally 16 "Occultazionisti" exchanged their experiences and discussed the coming projects. The successful event was very motivating for all participants.
Protocol,   Digital VTI,   Prepointing,   History,   1st observation in CH,   ESOP37-Review,   ESOP37-Lectures
September 8, 2018:   The astronomical exhibition AME2018 was successfully held in D-Villingen. The Swiss Astronomical Society and the magazine ORION participated to this event too. The topic of this year was dedicated to the useful observations of stellar occultations by asteroids. The observing campaigns are coordinated by IOTA-ES, the European Section of the International Occultation Timing Association. Please enjoy some impressions:
Picture 1: Helen Oertli (orionmedien), Christian Wernli (president of SAG), Thomas Baer (editor of ORION)
Picture 2: Helen Oertli (orionmedien)
Picture 3: Sven Melchert (president of VdS).
August, 2018:   Meeting of the Stellar Occultation Timing Association Switzerland (SOTAS), Bellinzona
Invitation,   Registration
May 13, 2018:   New: The Swiss Occultation Numbers, a monthly statistic about the observing activities of SOTAS members, was launched.
April 21, 2018:   Great success for SOTAS members: At 00:31 UT, the shadow of (130) Elektra, a 180 km asteroid, crossed Europe with center line directly along Switzerland. After good preparation works (workshop) and thanks to brillant weather conditions along the whole path, totally 9 (nine!) SOTAS stations recorded the disappearance and reappearance of the light of a 11.6 mag star. Eric Frappa (Euraster) arranged the chords and simulated the suitable model of the asteroid. Well done guys!
See the observations in detail...
April 5, 2018:   Announcement: On August 24 - 26, 2018, the 37th European Symposium on Occultation Projects (ESOP) will be held in CZ-Rokycany (near Pilsen).
March 30, 2018:   Dave Herald published the Summary Report of asteroidal occultations. It includes the observations during the year 2017. The publication is expected in the coming Minor Planet Circular.
More reports...
Dec. 30, 2017:   Oliver Klös (IOTA-ES) updated the list of Asteroid Occultations in Europe with target stars brighter than 9 mag. Call for observation: (788) Hohensteina (Feb. 22) and (129) Antigone (Feb. 23). Thanks to Oliver for the information.
Nov. 9, 2017:   Four times a year, the Journal for Occultation Astronomy (JOA) will be published by IOTA-ES. The magazine contains helpful information, reports and predictions concerning occultations. The journal is free, except the latest two issues (available with membership).
Wanted: Writers for the magazine. Who can imagine to write for the magazine? Please contact me.
Nov. 6, 2017:   Grazing occultation of Aldebaran by the moon: Between 03:14 and 03:18 UT, the star Aldebaran (alpha Tauri) was occulted in a grazing pattern caused by the limb profile of the moon. The observing path of this spectacular event passed Eglisau, a small town North of Switzerland. Stefan Meister prepared and organized an excellent observing campaign. Unfortunately, and once more, sky was clouded out during the interesting moments.
Oct. 5, 2017:   Star occultation by Triton: After an extra workshop and numerous previous successful tests, we all felt ready for the rare occultation event. Unfortunately, the weather was clouded out, stormy and/or rainy all over Switzerland exactly during the occultation event. Only one station reported an observation!
Summary and what we expected to see! Results
Sept. 18, 2017:   SOTAS has got a forum! Discuss your projects and stay informed. Register for automatic messages.
Special thanks to SAG for hosting the forum.
Sept. 16, 2017:   Meeting with workshop at the observatory Bülach, considering the technics of recording and video time inserter. Goal: The participants are ready to record the occultation by Triton on Oct. 5, 2017.
Tips and recording schedule.
Sept. 15-19, 2017:   The 36th European Symposium on Occultation Projects (ESOP) was held in D-Freiberg. There were no participants from Switzerland. Program with Lectures and Abstracts.
Aug. 19, 2017:   A new Website referring to the occultation by Triton was launched: Therein the MIT Planetary Astronomy Lab and the Deutsches SOFIA Institut will actualize the relevant information for planning and observation of the stellar occultation by Triton.
July 1, 2017:   A Map of the Triton Occultation shows the path of the shadow and further information about the occultation circumstances on October 5, 2017.
June 30, 2017:   Steve Preston and Oliver Klös published the Calls for Observations of asteroidal occultations in Europe (target star brighter than 9 mag).
June 7, 2017:   Dave Herald published the Summary Report of asteroidal occultations. It includes the observations from 2015/08/07 to 2017/02/10. The publication is expected in Minor Planet Circular no. 104988.
More reports...
June 2, 2017:   "3 - 2 - 1 - lift off" for the new working group! Let's occult!