Sidereus Nuncius
The first telescopes appeared in the Netherlands in 1608 when Middelburg spectacle-maker Hans Lippershey tried to obtain a patent on one. By 1609 Galileo had heard about it and built his own improved version. He probably was not the first person to aim the new invention at the night sky but his was the first systematic (and published) study of celestial bodies using one. One of Galileo's first telescopes had 8x to 10x linear magnification and was made out of lenses that he had ground himself. This was increased to 20x linear magnification in the improved telescope he used to make the observations in "Sidereus Nuncius".
Leibniz Institute for Astrophysics Potsdam
The first new instruments were delivered in the spring of 1914. The 65 cm refractor — the first big astronomical instrument manufactured by the famous enterprise of Carl Zeiss Jena — was mounted in 1915, whereas the completion of the 122 cm reflector telescope was delayed until 1924 by the First World War. Struve died in 1920 from an accident, and his successor was Paul Guthnick, who introduced in 1913 photoelectric photometry into astronomy as the first objective method of measuring the brightness of stars. When the 122 cm telescope (at this time the second largest in the world) was finished, the Babelsberg Observatory was the best-equipped observatory of Europe.