The Archenhold Observatory () was named in honour of

Friedrich Simon Archenhold Friedrich Simon Archenhold (2 October 1861 in Lichtenau, Westphalia – 14 October 1939 in Berlin) was an astronomer who founded the Treptow Observatory (today the Archenhold Observatory) in Berlin-Treptow. He graduated from the Realgymnasium in ...

, is an

observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed. His ...

in Berlin-Treptow. It houses the ''Großer Refraktor'' (Great Refractor), which is the longest pointable

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

in the world. It is also called the ''Himmelskanone'' (Celestial Cannon).

History

Industrial Exposition

The Archenhold Observatory began as a temporary installation at the 1896 Great Industrial Exposition of Berlin. At the initiative of

Wilhelm Foerster Wilhelm Julius Foerster (16 December 1832 – 18 January 1921) was a German astronomer. His name can also be written Förster, but is usually written "Foerster" even in most German sources where 'ö' is otherwise used in the text. Biography A ...

and Max Wilhelm Meyer, it was intended to present scientific and astronomical knowledge to the general public. Plans for a large

that

had been working on were invoked for this purpose. Although his plans were for a research instrument, its design was already being criticised at the time. Admittance charges at the exposition were intended to finance the construction and later relocation of the instrument. The telescope was erected in the

Treptower Park Treptower Park (, with a silent ''w'') is a park alongside the river Spree in Alt-Treptow, in the district of Treptow-Köpenick, south of central Berlin. History It was the location of the Great Industrial Exposition of Berlin in 1896. It is ...

and sheltered in a wooden building that also provided exhibition space and a lecture theatre. When the industrial exposition opened on 1 May 1896, the Great Refractor was still unfinished; it began operation in September 1896. The telescope has an aperture of and a focal length of ; the movable mass is 130 metric tons. Due to the late completion there was no finance to move the telescope after the exposition. At the end of 1896 the city of Berlin gave permission for the observatory to remain in Treptower Park. Archenhold, without an astronomer's salary, decided to turn the installation into a

public observatory A public observatory is an astronomical observatory mainly dedicated to public and educational purposes. It is often supported by a municipality, a school or an astronomical society. The primary purpose of public observatories is to offer exte ...

. It was operated by a society, the ''Verein Treptow-Sternwarte e. V.'' with Archenhold as president. This is now considered the oldest and largest public observatory in

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

. The exhibition covered themes like history of astronomy, Earth and Moon, Sun and planets, comets and meteors, stars and star clusters, instruments and optics. Observations included standard objects,

lunar eclipses A lunar eclipse occurs when the Moon moves into the Earth's shadow. Such alignment occurs during an eclipse season, approximately every six months, during the full moon phase, when the Moon's orbital plane is closest to the plane of the Earth ...

comets A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are ...

and the

Nova A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramati ...

Cygni 1903. 23,000 visitors attended in 1897, the number rising to 60,000 by 1899 and remaining about constant until the 1930s.

New building

In 1908, the original wooden building was demolished and on 4 April 1909 a new building was inaugurated. On 2 June 1915,

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

gave his first public talk about

General Relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics ...

at the observatory. In 1931, Friedrich Simon Archenhold was succeeded as director by his son Günter Archenhold. Due to his Jewish ancestry, he was forced to resign in 1936. The family was expelled from the observatory; some emigrated, others ended up in

Nazi concentration camps From 1933 to 1945, Nazi Germany operated more than a thousand concentration camps, (officially) or (more commonly). The Nazi concentration camps are distinguished from other types of Nazi camps such as forced-labor camps, as well as concen ...

. The observatory was integrated into the city's school system. During

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

a bomb hit the southwest wing, but the Great Refractor was not severely damaged. Observations resumed as soon as July 1945 for the

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six month ...

. Edgar Mädlow was interim director, assisted by Herbert Pfaffe.

Naming after Archenhold

In 1946 the city of Berlin renamed the observatory ''Archenhold-Sternwarte''. On 1 June 1948

Diedrich Wattenberg Diedrich Wattenberg (13 June 1909 – 26 November 1996) was a German astronomer. He was a prolific populariser, writer and speaker on his subject, becoming in the 1950s a familiar presence on radio and, later, television programmes. Life Watte ...

, who had been working with Archenhold, was made director. Annual visitor numbers rose from 8,000 in 1946 to 25,000 in 1949. In 1958, the Great Refractor was decommissioned, but retained as a monument of technology. From 1959 onwards, the observatory was increasingly used for school education in physics and astronomy. To support this, in the 1960s, two further domes were erected in the grounds. A lecture theatre was also added, and in 1966 the solar physics cabinet was created, which could project the Sun at diameter or a solar spectrum at length. In November 1976, Wattenberg retired and Dieter B. Herrmann was made director of the observatory. In March 1982, the

planetarium A planetarium ( planetariums or ''planetaria'') is a theatre built primarily for presenting educational and entertaining shows about astronomy and the night sky, or for training in celestial navigation. A dominant feature of most planetarium ...

was replaced. 1983 saw the completion of the reconstruction of the Great Refractor, which had started in 1977. Annual visitor numbers during the 1980s were around the 70,000 mark. Archenhold had already suggested a major planetarium. This became reality in 1987 when the

Zeiss Major Planetarium The Zeiss Major Planetarium (German ) is a planetarium in Berlin, and one of the largest modern stellar theatres in Europe. It is located on the borders of the Ernst-Thälmann-Park housing estates in the Prenzlauer Berg locality of Berlin. ...

was built in the

Ernst-Thälmann-Park Ernst-Thälmann-Park is a park in the centre of the Prenzlauer Berg district in Berlin. It was laid out in 1986 at the site of a former coal gas plant and named after the former Communist party leader Ernst Thälmann (1886-1944). The former pl ...

. Until 2013 it and the Archenhold Observatory formed a single organisational entity.

Berlin re-united

After

German reunification German reunification (german: link=no, Deutsche Wiedervereinigung) was the process of re-establishing Germany as a united and fully sovereign state, which took place between 2 May 1989 and 15 March 1991. The day of 3 October 1990 when the Ge ...

in 1990, the observatory came under control of the city's school administration. Significant repairs of the Great Refractor had to be carried out in 1989/1990 and 1995. As of 2018, the telescope remains operational and is available for night observing. The observatory underwent major refurbishment in 1995/1996. The exhibition was also completely revised. Since 2002, the observatory belongs to the

German Museum of Technology (German Museum of Technology) in Berlin, Germany is a museum of science and technology, and exhibits a large collection of historical technical artifacts. The museum's main emphasis originally was on rail transport, but today it also features e ...

. Dieter B. Herrmann retired in 2005. The observatory was then led for a while by the head of the astronomy department of the technology museum, Klaus Staubermann. In 2009, Felix Lühning became director of the Archenhold Observatory.

Equipment

Great Refractor

The Great Refractor was built in 1896 for the Great Industrial Exposition of Berlin. With an aperture of , a

focal length The focal length of an optical system is a measure of how strongly the system converges or diverges light; it is the inverse of the system's optical power. A positive focal length indicates that a system converges light, while a negative foca ...

of and a movable mass of 130 metric tons, it is considered a masterpiece of technology. The lenses were made by C. A. Steinheil & Söhne. Since 1967, the telescope is a protected monument.

Zeiss Small Planetarium

The

is located in an dome with 38 seats. In 1959 it was the first Zeiss Small Planetarium in the GDR. In 1982 it was replaced with the more modern ZKP-2 projector. In 1994 the planetarium room was refurbished.

Solar physics cabinet

The solar physics cabinet is situated in the grounds of the observatory. It was designed and built in 1965 by Diedrich Wattenberg and Erwin Rolf. A

coelostat A solar telescope is a special purpose telescope used to observe the Sun. Solar telescopes usually detect light with wavelengths in, or not far outside, the visible spectrum. Obsolete names for Sun telescopes include heliograph and photoheliograph ...

redirects the light from the Sun into the building. The sunlight is optionally dispersed into the spectral colours through four 60° prisms. With an

H-alpha H-alpha (Hα) is a specific deep-red visible spectral line in the Balmer series with a wavelength of 656.28 nm in air and 656.46 nm in vacuum; it occurs when a hydrogen electron falls from its third to second lowest energy level. H-alph ...

filter it is possible to observe prominences and active regions on the Sun.

Additional telescopes

In 1962, two observing domes were erected in the grounds north of the main building. These have diameters of and , resp. They house a Zeiss Cassegrain telescope ( aperture, focal length) and a refractor with

coudé focus A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century by Isaac Newton as an alternat ...

( aperture, focal length). Two further domes on the roof of the main building house an

astrograph An astrograph (or astrographic camera) is a telescope designed for the sole purpose of astrophotography. Astrographs are mostly used in wide-field astronomical surveys of the sky and for detection of objects such as asteroids, meteors, a ...

( aperture, focal length) and the historic Urania Refractor of 1888, which was transferred from the Berlin Urania. Two further shelters with roll-off roofs on top of the main building contain a comet seeker ( aperture, focal length) and a

Newtonian telescope The Newtonian telescope, also called the Newtonian reflector or just a Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton, using a concave primary mirror and a flat diagonal secondary mirror. Newton' ...

( aperture, focal length).

Reference

* Diedrich Wattenberg: ''Die Archenhold Sternwarte Berlin-Treptow.'' Berlin 1956. * Diedrich Wattenberg: ''75 Jahre Archenhold-Sternwarte.'' Festgabe. Berlin-Treptow 1971 (Archenhold-Sternwarte Berlin-Treptow. Vorträge und Schriften, 41). * Dieter B. Herrmann: ''100 Jahre Archenhold-Sternwarte''. 2. Auflage, paetec Gesellschaft für Bildung und Technik, Berlin 1996, . * Dieter B. Herrmann: ''Sterne über Treptow – Geschichte der Archenhold-Sternwarte.'' (herausgegeben vom Rat des Stadtbezirks Berlin-Treptow, Abteilung Kultur) Heimatgeschichtliches Kabinett, Berlin 1986.

External links

*
Förderverein der Archenhold-Sterwarte und des Zeiss-Großplanetariums Berlin e. V.
{{Authority control Astronomical observatories in Germany Museums in Berlin Science museums in Germany Buildings and structures in Treptow-Köpenick World's fair architecture in Germany Great refractors