Σ II 2 in the Struve Double Star Catalog, and together with a 14th-magnitude star as β 550 in the Burnham Double Star Catalogue. Observation Aldebaran is one of the easiest stars to find in the night sky, partly due to its brightness and partly due to being near one of the more noticeable asterisms in the sky. Following the three stars of Orion's belt in the opposite direction to Sirius, the first bright star encountered is Aldebaran. It is best seen at midnight between late November and early December. The star is, by chance, in the line of sight between the Earth and the Hyades, so it has the appearance of being the brightest member of the open cluster, but the cluster that forms the bull's-head-shaped asterism is more than twice as far away, at about 150 light years. Aldebaran is 5.47 degrees south of the ecliptic and so can be occulted by the Moon. Such occultations occur when the Moon's ascending node is near the autumnal equinox. A series of 49 occultations occurred starting on 29 January 2015 and ending at 3 September 2018. Each event was visible from points in the northern hemisphere or close to the equator; people in e.g. Australia or South Africa can never observe an Aldebaran occultation since it is too far south of the ecliptic. A reasonably accurate estimate for the diameter of Aldebaran was obtained during the occultation of 22 September 1978. In the 2020s, Aldebaran is in conjunction in ecliptic longitude with the sun around May 30 of each year. With a near-infrared J band magnitude of −2.1, only Betelgeuse (−2.9), R Doradus (−2.6), and Arcturus (−2.2) are brighter at that wavelength. Observational history On 11 March AD 509, a lunar occultation of Aldebaran was observed in Athens, Greece. English astronomer Edmund Halley studied the timing of this event, and in 1718 concluded that Aldebaran must have changed position since that time, moving several minutes of arc further to the north. This, as well as observations of the changing positions of stars Sirius and Arcturus, led to the discovery of proper motion. Based on present day observations, the position of Aldebaran has shifted 7′ in the last 2000 years; roughly a quarter the diameter of the full moon. Due to precession of the equinoxes, 5,000 years ago the vernal equinox was close to Aldebaran. Between 420,000 and 210,000 years ago,