The report presents an analysis of the history of the Public Astronomical Observatory (NAO) "Yuri Gagarin", the city of Stara Zagora, which was officially opened on February 26, 1961. The initiative to open it belongs to a group of enthusiasts, among which the figure of Boncho Bonev is of particular importance. With financial and material assistance from the municipality of Stara Zagora, the first premises were equipped and the first astronomical instruments and equipment were purchased. The observatory bears the name of the world's first pilot - cosmonaut Yuri Gagarin. The natural evolution of the development of the Observatory is presented, as well as the need of creation an observational base outside the city, in the area of the Ayazmo Park (opened in 1968). The supply with amateur telescopes is shown, as well as of a large optical instrument for professional astronomical work – a refractor (200/3000 mm), the Kude system, the production of the Carl Zeiss, Jena (former East Germany). The acquired ZKP-2 planetarium at the Carl Zeiss factory in Jena expands the NAO's capabilities in the education and promotion of astronomy and space science.The evolution of extracurricular astronomy training and the mass popularization of the achievements of astronomy, aeronautics, physics and human technology in PAOP are analyzed, as well as scientific observations of artificial Earth satellites. In this connection, in 1979 a specialized out-of-town observation base was built in the area of the Stara Zagora Mineral Baths, equipped with one of the most modern devices of its time – the AFU-75 satellite camera. An attempt was made to periodize the history of PAOP «Yu. Gagarin», the main stages being arranged in time according to significant historical, technological, organizational or other events.