With increasing industrialisation and the growing importance of shipping to the city, the exact measurement of time became a crucial role of the observatory, and a time ball was installed in the port with an underground electrical link to the observatory. There was a price to pay for the development to which the observatory itself was contributing; light pollution, and vibration and dust from street traffic eventually became such serious problems that Rümker and Richard Reinhard Emil Schorr (1867 – 1951), then an “observator” at the observatory, proposed to move the observatory to the current location in Bergedorf in 1892, although the official inauguration did not actually occur until 1912 under Schorr’s directorship (12 years after Rümker’s death in 1900). New instruments were ordered; the principal ones in the new observatory were the Meridian Circle and Great Refractor (60cm diameter) from Repsold, the 1m Reflector from Carl Zeiss, the Lippert Astrograph (purchased with a generous donation from Eduard Lippert, a local merchant) and of course the 26cm equatorial from the previous location. The move to Bergedorf ushered in the peak of Hamburg Observatory’s productivity; it was at this time one of Europe’s largest observatories, with Germany’s largest reflecting telescope and one of the world’s most powerful refractors.6, 19  

Fig. 5. With an increase in trade, light and smoke from the busy harbour soon became a major problem to Hamburg Observatory.20

Fig. 6. Richard Schorr.20

Throughout the 1910s and 1920s, the Great Refractor saw much use by Professor Kasimir Graf (1878 – 1950), who joined the observatory as an assistant in 1902, and became an “observator” in 1909. His observations of the planets were particularly impressive (although in 1924 he convinced himself that he had seen the now-infamous Martian “canals”). He left Bergedorf to become the director of the Vienna observatory in 1928.7, 19 In one of the few instances of professional-amateur collaboration at Bergedorf, his role in collaboration with local amateur Max Beyer is discussed below.

Fig. 7. The construction of the domes for the meridian circle in Bergedorf, 1908.20

In 1920, Walter Baade (1893 – 1960), one of Hamburg’s most famous astronomers, joined the observatory as Schorr’s assistant. This was despite his personally stated goal of working at one of the large American observatories, a goal which under the political and economic conditions of the time was quite unrealisable (during the founding of the International Astronomical Union, it was decided that German astronomers could not be members, a move justified at the time by the willing collaboration of some German scientists in the service of the military, and hence their perceived duplicity in World War I gas attacks in Belgium and France.8). Hamburg was literally Baade’s “next best choice”. From 1920 – 1931, Baade used the 1m reflector, first as an assistant, then as the sole observer. Initially he concentrated on the familiar Bergedorf material – comets, planets and asteroids \226 but then his observing programmes widened to stars in the galactic halo, and later he showed special interest in the “spiral nebulae”. The instrument was also critical for Baade’s work on his two-stellar-populations theory. In 1931 he achieved his dream, and accepted a position at the Mount Wilson observatory in California, much to Bergedorf’s disappointment.9, 19

Bernhard Schmidt (1879 – 1935) was born in Estonia and had an interest in science and mathematics from a young age. In 1926 he sought a role at Potsdam Observatory, but was looking for independent work, rather than the sort of supervised, structured programme offered by Potsdam. Schmidt preferred Bergedorf’s more flexible approach, and the observatory provided him with rooms and materials. He was to become another of Bergedorf’s famous astronomers, and it was the observatory’s willingness to allow him his own personal, independent working style which undoubtedly contributed to his innovations.

Fig. 8. Bernard Schmidt (left) in 1935.20

Schmidt began to think about how he might design and build an astronomical camera capable of working over wide angles with low focal ratios and with high resultant image quality. His now hugely celebrated Schmidt corrector plate was born on an eclipse expedition (with Baade) in the Philippines. The first Schmidt corrector plate was built in the winter of 1929, and it was to revolutionise photographic astronomy. The first actual “Schmidt telescope” was constructed in 1930 and produced images dramatically superior to their predecessors.21 The success of this innovation needs no further comment, and his work is commemorated at the Bergedorf observatory in a small museum inaugurated in 1979.22

Fig. 9. The world’s first Schmidt telescope (constructed in 1930 at Hamburg Observatory), here seen in 1932.20

The AGK2 (Astronomische Gesellschaft Katalog 2) was a stellar position project consisting of 200,000 stars, for which observations began in 1928. Bergedorf completed 50% of the work, the rest being completed by Pulkovo and Bonn observatories. Owing to the outbreak of World War II, however, it was not published until 1951.10 In addition to a large contribution to AGK2, between 1920 and 1953 Bergedorf astronomers Schwassmann and Wachmann used the Lippert astrograph to catalogue the spectra of 160,000 stars (the Bergedorfer Spektraldurchmusterung). Such work from Bergedorf and other observatories contributed significantly to the development of stellar evolution theory, including the Hertzsprung-Russell diagram familiar to astronomy students the world over.19

Fig. 10. Sample pages from the AGK2 catalogue.20

By the mid thirties, the question of a successor was increasingly on Schorr’s mind, and for him there was a natural choice: Walter Baade, who of course by now was at Mount Wilson in California. Mount Wilson was already in the process of building its own 1.2m Schmidt telescope, and Baade knew that Hamburg would require one with urgency if it were to compete with the American facility. Financial delays in Bergedorf seemed increasingly likely, whereas the Mount Wilson project was progressing rapidly. In a telegram sent to Schorr 1937 July 19 from Mount Wilson, Baade wrote (translation in brackets is the author’s):

HABE MIT SCHWEREN HERZENS FUER MT WILSON ENTSCHIEDEN STOP HOFFE DASS DIE HEIMAT MICH VERSTEHT [I have with a heavy heart decided on Mt Wilson STOP I hope that the homeland understands].11

This was a bitter blow to Schorr, whose next choice was Otto Heckmann. Heckmann had interests in cosmology, and in particular looked favourably on relativity theory, but the Nazi regime did not approve of such “non-German physics”. With the greatest difficulty on Schorr’s part, however, Heckmann became director in 1941.12 In fact, owing to the outbreak of the war, the 1.2m Schmidt telescope was not delivered to Bergedorf until 14 years after Baade’s decision, in 1951.13, 19

In the years before the outbreak of World War II, light pollution from Hamburg city was becoming an increasing problem, and more frequent air traffic meant that pilots required better orientational assistance when flying at night. Regular flights had begun between Hamburg and Berlin, and between Malmø in Sweden and Hannover. In 1925, the first navigational aid lights were installed in and around Hamburg, and this was the beginning of the era of light pollution with which so many near-city observatories became plagued. The observational side of Bergedorf’s work was never fully to recover.14