The Bohnenberger Observatory at Hohentübingen Castle is restored and can be visited once more!
The Museum of the University of Tübingen MUT has thus been given the museum use of the historically significant observatory from Johann G. F. Bohnenberger at Hohentübingen Castle. This is all the more significant, as the small observatory was constructed 200 years ago specifically for the so-called “Reichenbach’ Repetitive Circle”; a device which could be put back onto its original place again 16 years later. Only a few repetitive circles exist worldwide, for example in Florence, Milan and Paris. However, the historically unique entire ensemble consisting of the original device and the specifically for that constructed building which also presents the oldest ground observatory in the world, only exists in Tübingen. The renovation was concluded in September, 2018, – right on time for the 200-year festivity of the Württemberg land survey which started in this exact location.
We are very happy and would like to thank all departments, architects, restoration specialists, cooperation partners and collaborators in the redevelopment of this fantastic place! This presents another big step for the MUT, to – step by step – make the significant historical, scientific but also cultural-historical rooms, collections and locations accessible to the public. This also includes the Tübingen Castle Laboratory as cradle of biochemistry or the worldwide oldest giant wine barrel in the castle cellar, and the observatory, in addition to the outstanding collections in the Museum of Ancient Cultures.
Discover more about the observatory on the occasion of the reopening published publication “The Tübingen Castle Observatory” by the astronomy historic Jürgen Kost.
The Historical Observatory at the Castle Hohentübingen
After Württemberg had become a kingdom in 1806, King Wilhelm I. ordered the surveying and mapping of his empire. For the greatly enlarged country, the knowledge of its expansion was the basic prerequisite for a modern administration and a uniform tax law. Wilhelm I. entrusted the mathematician and astronomer Johann Gottlieb Friedrich von Bohnenberger (1765–1831), Professor for Mathematics and Astronomy at the University of Tübingen, with the task of national surveying in 1818. For the new mapping the kingdom, Bohnenberger placed the zero point of his measurements into the observatory, i.e. at the top of the northeast tower, which is why many Württemberg maps still orient themselves on this zero point today.
However, the castle was already used as astronomical observation spot before Bohnenberger: The Tübingen mathematician and physicist Georg Wolfgang Krafft (1701–1754) established the first observatory at the top of the northeast tower of the castle in 1752. And in the previous centuries, at the latest since the founding of the university in the year 1477, a significant astronomical tradition of Tübingen scholars and humanists, amongst others Johannes Stöffler (1452–1531), Johannes Kepler (1571–1630) and Wilhelm Schickard (1592–1635), had already existed.
The New Observatory on the Bastion
In order to improve the technical gear for the observatory, Johann Gottlieb Friedrich Bohnenberger ordered one of the most modern angle meters of his time in approximately 1812, a large repetitive circle from the company Reichenbach & Utzschneider in Munich. Bohnenberger had built the small observatory with a rotatable dome on the bastion specifically for the instrument delivered in 1814.
With the new observatory on the bastion, Bohnenberger wanted to determine coordinates of celestial objects. It was the age of position astronomy with the aim to be able to describe the movement of celestial objects, for example asteroids, through star maps. Only very few of these “Reichenbach’s repetitive circles” still exist today – amongst others in Paris, Milan or Florence. The combination of the original installation site and a nearly complete instrument, as the Tübingen Ensemble presents, is globally unique and a scientific attraction.
Soon after Bohnenberger’s death in 1831, the small observatory on the bastion was forgotten, until the Tübingen scientist Alfons Renz rediscovered the original instrument in the unimposing observatory in 2002. On the occasion of the 200th anniversary of the beginning of the Württemberg state survey, the Reichenbach repetitive circle was returned to the observatory in 2018 after it had been restored at the State Office for Monument Preservation.
Visit the Bohnenberger Observatory at Castle Höhentübingen
Wed to Sun 10am to 5pm
Thu 10am to 7pm
Free of charge
The Bohnenberger Observatory will be visited as part of the guided tour of the castle.
Museum Ancient Cultures