Jan Walery Jędrzejewicz was a medical doctor with active practice in Płońsk and an astronomer by passion. In fact, astronomy was a second profession for ‘Dr. Jedrzejewicz’, as he signed his astronomical publications. He built his own observatory in Płońsk, small village situated about 70 km from Warsaw, which he equipped with professional instruments. Thanks to that, he could perform precise astronomical observations. In the astronomical community, he was known and esteemed for his precise measurements of double stars. He also measured the position of many comets discovered at that times, including long-period ones. This study is devoted to the analysis of precision of Jędrzejewicz measurements on the examples of three long-period comets, today known as C/1885 X1 Fabry, C/1885 X2 Barnard and C/1886 T1 Barnard-Hartwig.

Jan WaleryJędrzejewicz是一名医生，曾在普沃斯克（Płońsk）积极从事医疗工作，并且是一位充满激情的天文学家。实际上，天文学是“博士”的第二职业。杰德热维兹（Jedrzejewicz），他签署了天文出版物。他在距华沙约70公里的小村庄普沃斯克（Płońsk）建造了自己的天文台，并配备了专业仪器。因此，他可以进行精确的天文观测。在天文界，他以对双星的精确测量而闻名。他还测量了当时发现的许多彗星的位置，包括长周期的彗星。这项研究致力于以三个长周期彗星（今天称为C / 1885 X1 Fabry，C / 1885 X2 Barnard和C / 1886 T1 Barnard-Hartwig）为例，对Jędrzejewicz测量的精度进行分析。