The construction of the 1m reflecting telescope at Hamburg Observatory marks the transition from classical astronomy to modern astrophysics. When it went into operation in 1911, it was the fourth biggest reflector in the world and for some time was the largest telescope in Germany, by aperture size. By 1920, the observatory director at the time, Richard Schorr, had recorded over 1.700 photoplates and discovered or rediscovered many minor planets and comets, primarily using the 1m Reflector.
Walter Baade, who worked with the instrument until 1931, increasingly dedicated himself to astrophysics. He succeeded in recording innumerable star clusters, gas nebulae and galaxies and he was first to prove the existence of isolated stars far outside the Milky Way.
The reflector has a diameter of 1m and a focal length of 15m. Remaining almost completely in its original state, this instrument is considered to be the most historically valuable instrument of Hamburg Observatory, with great significance for the history of science.
In 2013, the Förderverein Hamburger Sternwarte e. V. association refurbished the telescope in accordance with its original plans. Thanks to its special mounting by Zeiss the 1m Reflector is one of the most extraordinary constructions in the history of telescopes. In fact, one can easily move the instrument, despite it weighing 26 tonnes. Nowadays, it is not used for research but is instead used during public observation nights.
The building extension hosts the visitors centre of the Hamburg Observatory and the café „Raum & Zeit“ (“space & time”).
The Equatorial is a refracting telescope with a 26cm objective lens diameter and a focal length of 3m. It is the oldest telescope still in operation in Bergedorf – it had already been working in the old observatory in the city of Hamburg and moved to Bergedorf with the opening of the new observatory in 1909. The company A. Repsold & Söhne supplied the instrument in 1867, while the objective lens was produced by the company G. and S. Merz in Munich.
The name “Equatorial” refers to the mounting, which has one rotational axis along Earth’s rotation axis within the equatorial system of the Earth (equatorial or parallactic mounting). This was special at the time and allows adjustment of the telescope by rotating only one axis. Additionally, the instrument was equipped with big reference circles for the measurement of positions. A characteristic feature of this telescope is the wooden observer´s chair, which rotates on rails in the dome. It permits the astronomer to assume a comfortable position while observing.
The Equatorial is typical of classic astronomical instruments in the 19th century. At that time, the measurement of star positions was the primary task of observatories.
The Great Refractor
The Great Refractor of Hamburg Observatory is an early example for indurstrial cooperation. Tube and mounting are made by the Hamburg company A. Repsold & Söhne; the objective originates from Steinheil in Munich; dome and lifting platform are designed by Carl Zeiss in Jena.
A refractor is a telescope, which uses lenses, in contrast with a reflector telescope, which uses mirrors. A large objective lens, normally consisting of two lenses, produces an optical image. An astronomer can record this image directly at the telescope' s focal point with a photoplate or just take a closer look at it through an eyepiece. With 60cm diameter lenses and a focal length of 9m, the Great Refractor of Hamburg Observatory is one of the largest refractors in Germany. In the 19th century, refractors with long focal lengths were considered as default observatory equipment. Producing larger and larger lenses caused considerable problems though, so that in 20th century, reflectors gradually replaced the refractors.
Nevertheless, astronomers in Hamburg used the Great Refractor until 1980s for different scientific observations, e.g. for studying the Sun' s magnetic field or for measurements of the fast radio bursts of pulsars.
The Lippert Telescope
The Lippert Astrograph is named after its donor, Eduard Lippert, a prosperous merchant and amateur astronomer.
An astrograph is a light sensitive refracting telescope used for astrophotography. Originally, three astrographs were arranged in parallel, allowing simultaneous observation with different colour filters.
The building was completed in 1909; the instrumental equipment could only be finalised in 1914 though. Subsequently, the instruments were subject to several modifications. In 1957, a reflector with approximately the same focal length replaced the large astrograph. The other two astrographs were removed. The new reflector was again modified in 1974. Only the middle segments remained on the mounting, equipped with counterweights. Of the original instruments, only a guiding scope and a finder scope have been preserved.
The Lippert Astrograph helped discover several comets and numerous minor planets.
The Meridian Circle
When the observatory moved to Bergedorf in 1909, it obtained a meridian circle with a focal length of 2,3m and an aperture of 190mm, constructed by the company A. Repsold & Söhne.
The Meridian Circle is an astronomical telescope, which pivots only North-South only. With its help, one can define the transit time of a star through the meridian. The meridian is the supposed line that celestial bodies pass at their highest point over the horizon during the day.
The exact observation of meridian passages combined with the exact measurement of the altitudes above the horizon allows one to accurately determine a star’ s celestial coordinates.. Conversely, pre-determined stellar coordinates allow one to calculate the exact time (sidereal time). Such methods help determine the local time, the time for the time zones (CET) and the universal time (GMT or UT). Until World War II, the calculation and the announcement of time was one of the main functions of Hamburg Observatory.
Until 1964, the Meridian Circle in Bergedorf was used in two major projects to survey current star positions (AGK2 and AGK3). In 1967, the instrument was dismantled, modernised and shipped to Perth (Australia) for mapping the southern hemisphere.
The Oskar Luehning Telescope
Constructed in 1975, with a 1.2m diameter mirror, the Oskar Luehning Telescope is the largest and the newest telescope at Hamburg Observatory. The dome and the mounting date back to 1954 however. Initially, this building hosted the Great Hamburg Schmidt Spiegel that was later shipped to Spain.
A donation from the Nikolaus Luehning foundation financed the telescope in 1974. It is named after the son of Nikolaus, Oskar Luehning, who intended to study Astronomy, but died in World War II before he could.
Since 2001, the telescope has been equipped with a modern CCD camera, which has a field of view a quarter of the diameter of the moon. The computer-aided control of the dome and the telescope enables remote observations via the internet.
Besides the telescope, the building hosts a vaporisation plant for cleaning and coating mirrors.
The Salvador Spiegel
The Salvador-Spiegel is a Cassegrain telescope with a 40cm diameter objective and a focal length of 8m. It was installed around 1960. The instrument was used for measuring the brightness of stars. Today, it is used for public observations.
Images taken from telescopes with parabolic main mirrors show distortions even at relatively small distances from the optical axis. On these images, stars are point-like only in the centre of the picture; towards the edges, they are increasingly deformed. This problem impaired complete photographic mapping of the sky and reduced the ability to discover stars and galaxies.
Schmidt solved the problem with a new camera, the Schmidt camera, equipped with a corrector plate to compensate for the spherical aberration outside the optical axis. Schmidt' s first wide-angle telescope, completed in 1930, was a world sensation. After World War II, over 20 large Schmidt telescopes were installed globally. This was the beginning of the era of photographic sky survey.
The Great Schmidt Spiegel was inaugurated in 1954. However, since the observing conditions in Bergedorf were inadequate from the very beginning, the instrument was transferred to Calar Alto in the South of Spain in the early 1970s. The Schmidt Spiegel reached its prime with the “Hamburg Quasar Survey” (HQS) performed in Spain from 1985 to 1997.
Today, the era of photography in astronomy is over. In 2015, the Hamburg Schmidt Spiegel on the Calar Alto was equipped with a CCD camera and has been used remotely to observe asteroids and comets since.
The Sonnenbau (forefront) was constructed in the 1940s, especially for solar observations. Two boxes with movable mirrors (coelostats) were installed on the rails on the south side of the building. These coelostats redirected the sunlight into the building. After the war, this construction was used for some time to measure the weak global magnetic field of the Sun.
During the war, observations of the Sun were of major importance because of the impact of solar activity on radio communication on Earth. The measurements helped predict radio frequency interference, which was particularly significant for the high frequency radio communication on submarines. Besides the solar observatory in Bergedorf, at that time a number of this type of observatories was built in Germany. They were mostly located at higher altitude, in places with better observing conditions (such as Göttingen, Schauinsland, Zugspitze, Wendelstein). Some of these stations still exist.
In 2010, the Sonnenbau was reconstructed and since has been used as a seminar room and computer lab.
In 1876, at the location of the present Elbphilharmonie, a time ball was installed on the roof of the store Kaiserspeicher Nr. 1.
Every day, shortly before noon, a 1 m black ball was lifted in the tower and dropped 3m down exactly at noon, so that ship captains could set their on-board clocks for exact navigation.
Until 1934, the time ball in the port was controlled remotely by electric contacts at the pendulum clocks of Hamburg Observatory. The exact time was determined with the help of the Meridian Circle.