The Bamberg-Refraktor is a large telescope. The refracting telescope has an aperture of 320 millimetres, a focal length of five metres and is located in the Wilhelm Foerster Observatory in the Berlin district of Schöneberg.

The name "Bamberg" goes back to the builder of the telescope, Carl Bamberg (* 12. Juli 1847 in Kranichfeld; † 4. Juni 1892 in Friedenau), and the term "refractor" (Latin re = 'back' and frangere = 'refract') means that the telescope is made exclusively with light-refracting optical lenses and does not use mirrors or zone plates.

The 12-Zoll-telescope was built in 1889 in the Berlin workshops of Carl Bamberg in Friedenauer Bundesallee in Berlin, was at the time the largest telescope in the Kingdom of Prussia and the second largest in the German Empire after the refractor at the Observatoire de Strasbourg. It was characterised by careful manufacture, a large focal length and modern control technology. An electric clock was used for the largely automatic tracking of the telescope according to the hour angle of the object to be observed. The lenses were made of high-quality glass from the Glastechnisches Laboratorium Schott & Genossen in Jena. The total cost was 50,000 Mark, which corresponded to 250 kilograms of silver (Note: This amount of silver corresponds to a good 8,000 fine ounces with a market value (as of 2018/2019) of a good 100,000 euros).

Initially, it was not only available for research purposes, but primarily for the public in the observatory of the Urania on Invalidenstraße in Berlin, which was equipped with an electrically operated dome. Among the first astronomers working there were Friedrich Simon Archenhold and the co-founder of the Urania Wilhelm Foerster. With the refractor, the astronomer Gustav Witt discovered the asteroids (422) Berolina and (433) Eros in 1896 and 1898. The polar explorer Alfred Wegener, who was trained as an astronomer, also used the Bamberg refractor in the Urania.

During the Second World War, the building was severely damaged, but the glass lenses remained undamaged. The telescope was salvaged in 1951 and was repaired by the Askania workhouses in Berlin-Mariendorf. In 1955, it was set up as the largest operable telescope in Berlin on the grounds of the observatory of the Wilhelm Foerster Institute in General-Pape-Straße in Berlin, which had been built up since 1947 in the half-ruin of a former officers' mess by the two Berlin amateur astronomers Hans Rechlin and Hans Mühle and transferred to the Wilhelm-Foerster-Sternwarte Association in June 1953. The Bamberg-Refraktor was also used there for public demonstrations, but also for training astronomers. However, the light pollution from the nearby railway facilities at Südkreuz proved unfavourable for night sky observations, so a new location was sought.

In November 1961, the foundation stone was laid for the Wilhelm Foerster Observatory built with funds from the Deutsche Klassenlotterie Berlin on the Insulaner in Berlin-Schöneberg, which was piled up after the war as a mountain of rubble to a height of a good 78 metres. In 1962, Askania in Berlin-Mariendorf carried out a general overhaul of the telescope, and since the opening of the Wilhelm Foerster Observatory on 30 January 1963, the refractor in the largest dome of the public observatory has been the most important and frequently used instrument for demonstrations by the society. The movable dome with a diameter of eleven metres dates from 1905. It was no longer needed at the Berlin Zeiss-Ikon factories in Berlin-Friedenau and was given to the observatory.

Using the Bamberg-Refraktor, Adolf Voigt and Hans Giebler of the Berlin Lunar Observers Group made the roll film images for the Berlin Lunar Atlas from 1964 to 1969, which have since been made available as a digitisation. Today, the large refractor is mainly used for public demonstrations.

In 1996 and 1997 the Bamberg refractor was overhauled by Gebhard Kühn at Zeiss in Jena, and in 2020, it was equipped with a new electrically controlled tracking by the company 4H Jena-Engineering.