Imagine a summer day in 1704. Ole Rømer is beaming as he unveils his new creation Observatorium Tusculanum. This wasn’t just another observatory. It was Rømer’s personal project. He had longed for such a place for 30 years.
Observatorium Tusculanum represented freedom for Rømer. He was tired of adapting instruments to buildings. He wanted a building perfectly suited to his instruments. He expressed his frustration in a letter. He criticised observatories that were more for show than use.
Rømer chose Vridsløsemagle for several reasons. It was far enough from Copenhagen to ensure darkness and quiet. It shared the same latitude as Rundetårn. This made comparing observations easier. Though later it turned out to be a bit more to the North.
The name Tusculanum came from Cicero’s summer villa near Rome. Rømer’s father-in-law’s estate Pilenborg had the nickname Tusculum. The Observatorium Tusculanum was designed as a twin to Rundetårn Observatory. Rømer aimed to compare observations directly. He even thought it possible to communicate with light signals. This would synchronize the astronomical clocks.
Inside Observatorium Tusculanum Rømer housed groundbreaking instruments. The world’s first meridian circle stood here. Also a transit instrument for determining equinoxes. Four astronomical clocks completed the setup. The floor was lowered to protect against wind and vibrations. Instruments rested on three solid posts.
The building itself was simple but functional. Walls and the roof had slits for instrument sightings. Inside there were two rooms. One was a living space with a fireplace and bed. The other room was for observations only. It was unheated to prevent temperature fluctuations.
Rømer’s work at Observatorium Tusculanum led to significant discoveries. He made observations of stars and planets. In 1706 he spent three days observing. These observations later formed the basis for his theory on stars’ movements. He called these three days Triduum.
After Rømer’s death in 1710 the observatory fell into disrepair. In 1716-17 the instruments were moved to Rundetårn. Tragically a fire in 1728 destroyed everything including Rømer’s notes. Only the Triduum observations survived.
The location of Observatorium Tusculanum was lost. In 1765 an unknown writer searched for it but found nothing. An old woman remembered where the “star-watcher house” had been. Her details helped to indicate the location.
Many tried to find the site. But it was not until 1978 that Claus Thykier rediscovered it. He used old sightlines and maps. He located the sparse remains of the observatory.
Today the site is protected. You can see it near the Kroppedal Museum. The ground plan and instrument positions are marked. A bronze statue of Rømer stands nearby. It depicts him at the moment he discovers the speed of light.
Observatorium Tusculanum may be modest but its legacy is immense. It represents Rømer’s dedication to astronomy. It also highlights his innovative approach to instrument design. Take a moment to appreciate this place. It marks a pivotal point in astronomical history. It shows the importance of observation and innovation.