[JAN JĘDRZEJEWICZ AND EUROPEAN ASTRONOMY OF THE 2ND HALF OF THE 19TH CENTURY]

Jan Jędrzejewicz was an amateur astronomer who in the 2nd half of the 19th century created an observation centre, which considering the level of research was comparable to the European ones. Jędrzejewicz settled down in Plonsk in 1862 and worked as a doctor ever since but his greatest passion was astronomy, to which he dedicated all his free time. In 1875 Jędrzejewicz finished the construction of his observatory. He equipped it with basic astronomical and meteorological instruments, then began his observations and with time he became quite skilled in it. Jędrzejewicz focused mainly on binary stars but he also pointed his telescopes at the planets of the solar system, the comets, the Sun, as well as all the phenomena appearing in the sky at that time. Thanks to the variety of the objects observed and the number of observations he stood out from other observers in Poland and took a very good position in the mainstream of the 19th-century astronomy in Europe. Micrometer observations of binary stars made in Płońsk gained recognition in the West and were included in the catalogues of binary stars. Interest in Jędrzejewicz and his observatory was confirmed by numerous references in the English "Nature" magazine.