On January 12th at 9:20 p.m. CET, the asteroid of the main belt (994) Otthild covers a star visible with the naked eye in the constellation lynx. The 3.9 Mag Helle 38 Lyncis (HIP 45688) is a multiple system in which the bright A component is covered over Germany. The weaker B component with 6.0 MAG is located at a distance of only about 2.6 arch seconds and a position angle of about 222 degrees in the sky. Two other stars that also belong to the system are further away and only shine with a magnitude of 12.5. At the time of the cover, the target is about 37 degrees in height in the northeastern sky. The moon does not bother the observation, it is still under the horizon.
Shortly before the occultation, the star and the asteroid "merge" optically and the combined brightness of both objects increases slightly to around 3.7 mag. What then happens in the case of a occlusion differs by the observation method. When the star occultation takes place, the bright A component is hidden for a maximum of 2.1 seconds and we can catch a brief undisturbed view of the weak B component with a telescope or binoculars. With the naked eye, the star occultation becomes an extraordinary experience, because the star 38 Lyncis disappears from the sky for a short time.
The cover path
As with a solar eclipse, the star covering can only be observed in a shadow path - if the weather is part of it. Using position data for star and asteroid, the approximately 26 -kilometer shadow reaches the German -speaking area near Peenemünde around 9:20 p.m. CET. He crosses Germany in just more than 30 seconds and roams the Netherlands at Eindhoven. However, errors in the astrometric position of the light star should not be underestimated when calculating the path; The individual predictions deviate from each other by several kilometers in the position of the path. Therefore, all observation stations, also in the error limits and beyond, should try their luck. The pre -calculated path cards with zoom function can be called up in the Occult Watcher Cloud: path card 1 and path card 2
Visual observations can be measured using a stopwatch and a radio-controlled clock. The times of the beginning and end of the occultation must be determined as precisely as possible, as well as the geographical position of the observation station (longitude, latitude and altitude above the sea). Detailed instructions for visual observation can be found on the IOTA/ES website. Since the observation of a stellar occultation cannot be repeated, the sequence of the measurement should be practiced beforehand. Measurements with cameras are preferable to visual observations in terms of accuracy. However, bright star occultations are rare and one should not miss the experience of the "star eclipse" with the naked eye. Such a bright stellar occultation over Germany was last seen in July 2010 by the asteroid (472) Roma. At that time, more than 200 stations throughout Europe reported their observations.
