Denmark Copenhagen Copenhagen Observatory

Østervold Observatory

About

Østervold Observatory, also known as the Copenhagen University Observatory, was established in 1861 to replace the outdated Rundetårn observatory. Located on the former bastions of Copenhagen’s old fortifications, it offered improved conditions for astronomical research, away from the growing light pollution and vibrations of the city. Designed under the guidance of astronomer Heinrich Louis d'Arrest, the observatory became a center for groundbreaking studies in nebulas and stellar spectroscopy. It also housed the International Astronomical Union’s news service bureau from 1922 to 1965. Though no longer active in research, the building now serves the University of Copenhagen and stands as a monument to Denmark’s scientific heritage.

Copenhagen Denmark

Location

The Østervold Observatory, also known as the Copenhagen University Observatory, is located on Øster Voldgade 3 in Copenhagen, Denmark, on the city's old bastioned fortifications near the Botanical Garden and Rosenborg Castle. Built between 1859 and 1861 in a neoclassical style designed by Hans Christian Hansen, it replaced the older Rundetårn observatory, which had become outdated due to expanding instruments, city light pollution, and vibrations. The observatory housed important astronomical research and the Central Bureau for Astronomical Telegrams until the 1960s. Its notable instruments included a large refractor and a double refractor telescope, and it contributed significantly to star cataloging, spectroscopy, and astrophysics under distinguished astronomers such as Heinrich Louis d'Arrest and the Strömgrens. Nearby landmarks include the adjacent Botanical Garden, Rosenborg Castle with its gardens, and it is located close to central Copenhagen’s historic district. Although the observatory building is no longer used for astronomy today, it remains in good condition and now houses the Institute for Science Didactics of the University of Copenhagen. The location offers a rich combination of scientific heritage and proximity to both historic architecture and green spaces in the heart of the city, making it a culturally significant site for visitors interested in astronomy and Copenhagen’s history.