By the 50th anniversary of the Observatory, they had built an astrophysical laboratory with a mechanical workshop and installed the Europe's largest refractor, (30 inch). Astrophysical research really gained momentum with the appointment of Feodor Bredikhin as a director of the Observatory in 1890 and transfer of Aristarkh Belopolsky from the Moscow Observatory, an expert in stellar spectroscopy and solar research. In 1923, they installed a big Littrow spectrograph, and in 1940 – a horizontal solar telescope, manufactured at a Leningrad factory. After having received an astrograph in 1894, the observatory began its work on astrophotography. In 1927, the Observatory received a zone astrograph and with its help the Russian astronomers catalogued the stars of the near-polar areas of the sky. Regular observation of movements of celestial poles began with the construction of the zenith telescope in 1904. In 1920, the Observatory started transmitting the exact time by radio signals. The observatory participated in the basic geodesic work, namely in measuring degrees of the arc of the meridian from the Danube to the Arctic Ocean (until 1851), and in triangulation of Spitsbergen in 1899–1901. Military geodesists and hydrographers used to work at the Observatory as interns. The Pulkovo Meridian, which passes through the center of the main building of the Observatory and is located at 30°19,6‘ east of Greenwich, was the point of departure for all former geographical maps of Russia.