Category of Astronomical Heritage: tangible immovable
Rundetårn, Copenhagen, Denmark

Description

Geographical position

Rundetårn (Round Tower), , Købmagergade 52A (Pedestrian street), 1150 Copenhagen, Denmark

Location

Lat. 55° 40′ 52.86″ N, long. 12° 34′ 33.0204″ E, elevation 16m above mean sea level.

IAU observatory code

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Description of (scientific/cultural/natural) heritage

Fig. 1. Rundetårn (Round Tower), Copenhagen (Wikipedia)

The new observatory, the ten-storey round tower (Rundetårn), part of the Trinitatis church, was built in 1637/42 by the architect Hans Steenwinkel the Younger (1587--1639).

The gilded Rebus on the south facade, which includes the four Hebrew consonants, refers to the patron King Christian IV. (1577--1648), King of Denmark and Norway of 1588 to 1648: <i>Lead Jehovah, the right teaching and justice into the heart of the crowned King Christian IV, 1642</i>

Fig. 2. 209-m-Spiral Ramp ("Donkey Stairway") in Rundetårn, Copenhagen (Wikipedia, Mariano ZF Barcelona)

The 209-m-Spiral Ramp ("Donkey Stairway", Eselstreppe, equestrian staircase) is unique in European architecture.

The building (Stellaburgis Hafniens) was used for scientific purposes by the University of Copenhagen until 1861, as an astronomical observatory, as a student church and as a university library (founded in 1482).

The platform in 35-m height offers excellent observation conditions. Nowadays the observation deck affers a nice view of Copenhagen with all the towers and impressive buildings.
The platform is surrounded by a wrought-iron lattice (1643) made by Kaspar Fincke (1584--1655), Court Artist in metalwork, coming from Bohemia, with Christian IV’s monogram; in addition, the letters RFP, which represent the King’s motto: <i>Regna Firmat Pietas</i> (Piety Strengthens the Realms).

In the Great Fire of 1728 the Trinitatis Complex was severely damaged but was rebuilt. The Round Tower is the oldest observatory in Europe, still in operation, as a Public Observatory.

In 1929, a dome (7m high and 6m in diameter) was added on the observing platform.

History

Fig. 3. Rundetårn, Copenhagen, Rebus "1642" (Wikipedia, Christian Bickel)

The first director

Christian Sørensen Severin, called Longomontanus (1562--1647) began in 1589 as an assistant to Tycho Brahe in Uraniborg, studied from 1597 to 1602 in Breslau (Wrocław), Danzig (Gdańsk), Königsberg (Kaliningrad) and Rostock, and in 1605 was appointed as a first professor at the University of Copenhagen. His work Astronomia Danica (Amsterdam 1622) was dedicated to Christian IV.

He proposed to replace Tycho’s lost observatories Uraniborg and Stjerneborg, Island Hven, Denmark (today Ven, Sweden), which were destroyed in 1601.

In 1929 the platform on the tower was replaced by a dome.

State of preservation

The Rundetårn was built by Hans van Steenwinckel the Younger (1587--1639) in Dutch Baroque style (1637--1642), initiated by Christian IV of Denmark (1577--1648), King of Denmark and Norway of 1588 to 1648, and finished in 1643 by the Dutch architect Leonhard Blasius (ÔÇá1644), also Royal architect of Christian IV.
The building is still in good condition. Conservation status: Protected in 1932.

Comparison with related/similar sites

Fig. 3. Rundetårn, Copenhagen (1642), (Doppelmayr, Johann Gabriel: Atlas Coelestis in quo Mundus Spectabilis. Nuremberg: Homann’s Heirs 1742)

It is a very unique building at this time, a starting point for tower observatories -- comparable to other Mathematical Towers:
Clementinum Prague (1722), Zwehrenturm in Kassel (1710), Specola - Bologna Observatory (1712), Old Vienna Academy Observatory -- tower on the top (1755), Osservatorio Astronomico di Brera of the Jesuits in Milano (1762), Padova (Padua) Observatory (1767), Mannheim Observatory (1772).

Very large tower observatories are:
Kremsmünster, Austria (1749), Mathematical Tower of the University Breslau / Wrocław (1791), Bogotá Observatory, Columbia (1803).

Threats or potential threats

no threats

Present use

The Rundetårn is used as a public observatory.

Astronomical relevance today

The Rundetårn, Copenhagen, was used for scientific purposes by the University of Copenhagen (Library and Observatory) until 1861, then the light pollution from the surrounding city and vibrations caused by the ever increasing traffic in the streets below had made the observations inaccurate. Since then, no modern astronomy was produced any more, the tower is now used for public outreach.

A new Copenhagen observatory, the Østervold Observatory, on a bastion of the city fortifications was inaugurated in 1861 (Neoclassical style) to the design of Hans Christian Hansen (1803--1883), a famous Danish architect, influenced by Karl Friedrich Schinkel (1781--1841).

References

Bibliography (books and published articles)

Poulsen, Erling: Centuries of Astronomy -- Astronomy in Denmark (2009), https://web.archive.org/web/20090202090040/http://rundetaarn.dk/engelsk/observatorium/history.htm
Wolfschmidt, Gudrun (Hg.): Astronomie im Ostseeraum -- Astronomy in the Baltic. Proceedings der Tagung des Arbeitskreises Astronomiegeschichte in der Astronomischen Gesellschaft in Kiel 2015. Hamburg: tredition (Nuncius Hamburgensis -- Beiträge zur Geschichte der Naturwissenschaften; Band 38) 2018.