The story of the Observatory

Designed by Carl Ludvig Engel and completed on Tähtitorninvuori hill in 1834, the Observatory building was the most modern observatory of its time. For many decades, it served as a model for other observatories around the world. The Observatory was also the home of many professors of astronomy and their families. Since 2012 the Observatory has accommodated the University Museum's Centre for Astronomy.

The Helsinki Observatory was built between 1831 and 1834. The building was designed by architect Carl Ludvig Engel (1778–1840) and Professor of Astronomy F. W. A. Argelander (1799–1875). A few years earlier, Engel had designed a new observatory building constructed in Turku, which Argelander then finished so that it could be used for observation. After the Great Fire of Turku, the University relocated to Helsinki. The new capital also needed a new observatory.

Argelander had found a suitable location on the Ulricasborg hill (currently Tähtitorninmäki hill or “Observatory hill”). The building required an unobstructed view of the sky, but also had to be visible to the port because a time signal bag was dropped every day at noon from the mast of the Observatory’s Middle Tower to allow ships docked in the city’s southern port to check their chronometers. Correct timekeeping was essential for navigation.

Engel designed the Observatory as an “embellishment for the city”. The building came to dominate the Helsinki cityscape and constituted the southern terminal point of the city’s new north-south axis, Unioninkatu street. 

The difficulties involved in designing the building were compounded by new observation technology. A refracting telescope, which stood on a fixed mount and could be pointed in any direction of the sky, required a supporting structure in the form of a revolving tower with a rotating opening for observations. As many as three revolving observation towers were constructed on the roof of the Helsinki Observatory. Engel’s design of the Helsinki Observatory served as a model for the Central Astronomical Observatory of the Russian Academy of Sciences at Pulkovo in 1839, which in turn was followed by observatories in various locations across the world.

In 1890 a tower for the double refractor, i.e., photographic telescope, was completed in the Observatory garden. This telescope was used for the international Carte du Ciel project. The tower was designed by Gustaf Nyström (1856–1917). In 1901 the wing accommodating a dark room was extended with a pavilion for observations; this structure housed a fixed photographic telescope directed at the celestial pole.

The Observatory building has been renovated several times. In the large-scale bombings of Helsinki in 1944, the tower of the photographic telescope was badly damaged, but the Observatory itself was saved from severe harm.

As the city grew, lights and smoke increasingly began to hamper astronomical observations. Observation activities were transferred in the 1970s to the Metsähovi Observatory in Kirkkonummi, some 30 kilometres from Helsinki, and later to international observation sites (including those in the Canary Islands and Chile) and observation satellites.

In the student revolt of 1969, students demanded that the Observatory building be used for nothing but teaching and research. Their demand was satisfied, and the building’s professorial residence designed by Engel was converted into library and work facilities. Quarters were refurbished for the porter in the east wing and the west wing was converted into an instrument manufacturing and repair shop. For the Observatory’s 150th anniversary in 1984, the lecture room, the East and West Rotundas and the towers were renovated, and the Meridian Room was refurbished into an exhibition facility.

The Department of Astronomy was closed in 2010 as a result of a reform of Finnish universities, but a division of geophysics and astronomy was established under the Helsinki University's Department of Physics on the Kumpula campus. Today the astronomers continue their work under the division of particle physics and astrophysics. The Observatory building was renovated between 2011 and 2012.

The Observatory building now accommodates the Helsinki University Museum's Centre for Astronomy which is open to everybody interested in space and astronomy. The Centre for Astronomy especially aims to raise youth's interest in natural sciences.