1700

Introduction of the so-called 'Improved Calendar' in the Protestant states of Germany

10.5.1700

Enactment of the calendar patent for the Berlin Observator [Image]

18.5.1700

Appointment of Gottfried Kirch as director of the observatory

11.7.1700

Foundation of the Brandenburg Society

1711

Construction of the first observatory in Berlin [Images]

1832-35

Construction of the new observatory by Karl Friedrich Schinkel [Images]

1846

Discovery of the planet Neptune by Johann Gottfried Galle

1865

Appointment of Wilhelm Julius Foersters as director

1874

Foundation of the Astronomical Recheninstitut

1874

Foundation of the Astrophysical Observatory Potsdam (AOP)

1876-79

Construction of the main building of the AOP on the Telegrafenberg at Potsdam [Images]

1881

First Michelson experiment in Potsdam

1886

Discovery of canal rays by Eugen Goldstein

1888

Discovery of the polar motion of the Earth by Karl Friedrich Küstner

1888

First photographic determination of a radial velocity by Hermann Carl Vogel

1896

Experiments to find radio emission from the Sun by Johannes Wilsing and Julius Scheiner

1899

Completion of the Great Refractor at Potsdam [Images]

1904

Appointment of Karl Hermann Struve as director of the Berlin Observatory

1909

Berufung von Karl Schwarzschild zum Direktor des AOP

1911-13

Construction of the observatory in Babelsberg

1913

Relocation of the Berlin Observatory to Babelsberg

1913

Introduction of photoelectric photometry by Paul Guthnick in Babelsberg

1915

Completion of the Large Refractor in Babelsberg

1921-24

Construction of the Einstein Tower on the Telegrafenberg

1924

Completion of the 1.22-m telescope in Babelsberg

1931

Association of the Sonneberg Observatory to the Babelsberg Observatory

1.1.1947

Takeover of AOP and Babelsberg Observatory by the German Academy of Sciences

1954

Start of radio observations in Tremsdorf

1960

Completion of the 2-m telescope in Tautenburg

1969

Foundation of the Central Institute of Astrophysics

1.1.1992

Establishment of the Astrophysical Institute Potsdam (AIP)
Appointment of Karl-Heinz Rädler as scientific chairman

1998

Appointment of Günther Hasinger as scientific chairman of the AIP

2001

Appointment of Klaus G. Strassmeier as scientific chairman of the AIP

2004

Appointment of Matthias Steinmetz as scientific chairman of the AIP

The history of astronomy in Potsdam really began in Berlin in 1700. Initiated by Gottfried W. Leibniz, on July 11, 1700 the 'Brandenburgische Societät' -- the later Prussian Academy of Sciences -- was founded by the elector Friedrich III. in Berlin. Two months earlier the national calendar monopoly provided the funding for an observatory. By May 18 the first director, Gottfried Kirch, had been appointed. This happened in a hurry, because the profits from the national basic calendar, calculated and sold by the observatory, should have been the financial source for the academy. This kind of financing existed until the beginning of the 19th century, but the basic calendar was calculated until very recently --- it passed away after the 'Wende' in 1991.

In 1711 the first observatory was built in Dorotheen Street in Berlin and in 1835 a new observatory building, which was designed by the famous architect Karl Friedrich Schinkel, was completed in Linden Street (near Hallesches Tor). Alexander von Humboldt was then promoting astronomy by his famous 'Kosmos' lectures in 1827/28. He played an important role in providing the funds for both observatory and instruments.

The Berlin Observatory became known world-wide when Johann Gottfried Galle discovered the planet Neptune in 1846. The discoveries of the canal rays by Eugen Goldstein in 1886 in the physical laboratory of the observatory and of the variation in the altitude of the Earth's pole by Karl Friedrich Küstnerr in 1888 were likewise important.

The last two scientific events took place when Wilhelm Julius Foerster was director of the observatory, which was meanwhile attached to the University of Berlin. He prepared the basis for the astronomical observatories in Potsdam: in 1874 the foundation of the Astrophysical Observatory Potsdam on the Telegrafenberg and in 1913 the removal of the Berlin Observatory to Babelsberg.

In the middle of the 19th century spectral analysis was developed by Gustav Kirchhoff and Robert Bunsen. It provided the possibility of obtaining information on the physical parameters and chemical abundances of stars, by the spectral analysis of their light. Foerster recognized these possibilities and initiated the building of a solar observatory. in 1871 as a memorial to the crown prince, in which he emphasized the importance and profit of solar research, This idea was soon extended to the whole astrophysics.

The site of the observatory was chosen on a hill south of Potsdam, the Telegrafenberg, on which had been, from 1832 to 1848, a relay station of the telegraph for transmission of military information from Berlin to Koblenz. On 1 July 1874 the Astrophysical Observatory Potsdam was founded. Even before the construction of the observatory had started in the autumn of 1876, solar observations were being made from the tower of the former military orphanage in Linden Street in Potsdam by Gustav Spörer. The construction work started in 1876, and the main building of the observatory and its equipment were finished in the autumn of 1879.

The AOP was managed by a board of directors comprising Wilhelm Julius Foerster, Gustav Kirchhoff and Arthur Auwers. In 1882 Carl Hermann Vogel was appointed as sole director of the observatory. The main focus of his work was now on stellar astrophysics. He was the first successfully to determine radial velocities of stars photographically and as a result he discovered the spectroscopic binaries.

In 1899 what was then the largest refractor in the world, with lenses of 80 and 50~cm, manufactured by the firms of Steinheil and Repsold, was mounted in a 24-m dome. It was inaugurated in a great celebration by the German emperor, Wilhelm II. Although the Great Refractor of Potsdam did not realize all the hopes astronomers had for it, nevertheless two important discoveries should be mentioned: the interstellar calcium lines in the spectrum of the spectroscopic binary delta Orionis by Johannes Hartmann in 1904 and the presence of stellar calcium emission lines -- a hint on stellar surface activity -- by Gustav Eberhard and Hans Ludendorff about 1900.

Ten years later one of the most famous astrophysicists of this century, Karl Schwarzschild, became director of the observatory. In only a few years of work -- by 1916 he had died after a insidious illness -- he had made fundamental contributions in astrophysics and to General Relativity Theory. Only some weeks after publication by Einstein of his General theory, Schwarzschild found the first solution of the very complicated system of Einstein equations, which is now named after him as the 'Schwarzschild solution' and which is of fundamental importance for the theory of black holes.

There exist further close links between the AOP and Einstein's Relativity Theory. In 1881 Albert A. Michelson performed his experiments in an attempt to demonstrate the movement of the Earth through the hypothetical ether, in the cellar of the main building of the AOP. His negative results were fundamentally reconciled only through Einstein's Special Relativity Theory of 1905.

To prove the redshift of spectral lines in the gravitational field of the sun -- an effect proposed by Einstein's GRT -- was the aim of a solar tower telescope, which was built from 1921 to 1924 at the instigation of Erwin Finlay Freundlich. Though at that time it was not yet possible to measure the gravitational redshift, important developments in solar and plasma physics were started here and the architect, Erich Mendelsohn, created with this peculiarly expressionistic tower a unique scientific building.

Besides the work of Schwarzschild, in the following decades important observational programmes such as the ''Potsdamer Photometrische Durchmusterung'' and the outstanding investigations of Walter Grotrian on the solar corona found recognition all over the world.

At the end of the 19th century the Berlin Observatory, originally built outside the border of the town, was enclosed by blocks of flats and scientific observations were almost impossible. Therefore, Foerster proposed the removal of the observatory to a place with better observational conditions outside Berlin. In 1904 he appointed Karl Hermann Struve, former director of the observatory of K"onigsberg, as his successor to realize this project.

After test observations by Paul Guthnick in the summer of 1906 a new site was found on a hill in the eastern part of the Royal Park of Babelsberg. The ground was placed at the observatory's disposal by the crown free of charge. The costs of the new buildings and the new instruments amounted to 1.5 million Goldmark and could be covered by selling the landed property of the Berlin Observatory. The old observatary built by Schinkel was pulled down later. In June 1911 the construction of a new observatory began in Babelsberg and on 2nd August 1913 the removal from Berlin to Babelsberg was complete.

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 120 cm mirror telescope was delayed until 1924 as a result of the First World War. Struve died in 1920 from an accident, and his successor was Paul Guth\-nick, who introduced in 1913 photoelectric photometry into astronomy as the first objective method of measuring the brightness of stars. When the 120 cm telescope -- at this time it was the second largest in the world -- was finished, the Babelsberg Observatory was the best-equipped observatory of Europe.

The development of the photoelectric method for investigating weakly variable stars and spectroscopic investigations with the 120 cm telescope made the Babelsberg observatory well-known beyond Europe, too.

At the beginning of 1931 the Sonneberg Observatory founded by Cuno Hoffmeister was attached to the Babelsberg Observatory. For more than 60 years a photographic sky survey was carried out, which represents the second largest archive of astronomical photographic plates. This archive and the discovery and investigation of variable stars popularized the name Sonneberg all over the astronomical world.

With the beginning of the regime of fascism, the fortunes of astronomy in Potsdam as well as in Babelsberg started to decline. The banishment of Jewish co-workers played an essential role in this process. The beginning of the Second World War practically marked the cessation of astronomical research.

The new start after the war was very difficult. In Potsdam the Einstein Tower had suffered heavy damage by bombs, in Babelsberg valuable instruments, among them the 120 cm telescope, were dismounted and removed to the Soviet Union as war reparations.

In January 1947 the German Academy of Sciences took the Astrophysical Observatory Potsdam and the Babelsberg Observatory under its administration, but it was not until the beginning of the 1950s before astronomical research started anew.

In June 1954 the Observatory for Solar Radio Astronomy in Tremsdorf (17 km distant south-east from Potsdam) began its work as a part of the AOP. The history started in 1896: after the discovery of the radio waves by Heinrich Hertz in 1888, Johannes Wilsing and Julius Scheiner, fellows of the AOP, tried to detect radio emission from the Sun. They did not succeed, because of the low sensivity of their equipment. After the Second World War Herbert Daene started once again to attempt radio observations of the Sun at the site of Sternwarte Babelsberg and these were continued in Tremsdorf. In October 1960 the 2m telescope built by Carl Zeiss Jena was inaugurated in the Tautenburg Forest near Jena and the new Karl Schwarzschild Institute was founded. The Schmidt variant of this telescope is up to now the largest astronomical wide-field camera in the world and it was the main observational instrument of the astronomers of the GDR.

In 1969 the four East-German astronomical institutes, Astrophysical Observatory Potsdam, Babelsberg Observatory, the Thuringian Sonneberg Observatory, and Karl-Schwarzschild Observatory Tautenburg, were joined in the course of academy reform to the Central Institute of Astrophysics of the Academy of Sciences of the GDR. The Solar Observatory Einstein Tower and Observatory for Solar Radio Astronomy were affiliated later.

One part of the scientific activities concerned cosmic magnetic fields and cosmic dynamos, phenomena of turbulence, magnetic and eruptive processes on the Sun, explosive energy dissipation processes in plasmas, variable stars and stellar activity. Another part was directed to the early phases of cosmic evolution und the origin of structures in the Universe, large-scale structures up to those of superclusters and to active galaxies. In this connection special methods of image processing have been developed. In addition, investigations in astrometry have also been performed.

The scientific work of the Zentralinstitut für Astrophysik suffered strongly from the isolation of the GDR from the western world. It was very difficult to come into contact with western colleagues. When in the autumn of 1989 the 'Wall' was demolished, new possibilities at once arose.

On the basis of the prescriptions of the 'Einigungsvertrag' for the Academy of Science of the GDR, the Central Institute of Astrophysics was dissolved on 31st December 1991. On the recommendation of the Wissenschaftsrat on 1st January 1992 the Astrophysical Institute Potsdam, with a greatly reduced staff, was founded. The Sonneberg Observatory and the Karl Schwarzschild Observatory Tautenburg are no longer affiliated to the Astrophysical Institute Potsdam.