The historic Elberfeld table planetarium

In 1828, the Elberfeld carpenter Heinrich Aeuer completed an extraordinary instrument, which today awaits its return to Wuppertal in the catacombs of the Deutsches Museum in Munich.

The 19th century saw a steady increase in the popularisation of science among the population. Scientific enthusiasm was not limited to academic circles. An extraordinary example of this is the Elberfeld carpenter Heinrich Aeuer, who built a fascinating tabletop planetarium between 1820 and 1828 and wove in conjectures about the planets that only proved to be scientifically correct 150 years later.

Michael Winkhaus, Director of Studies at Carl-Fuhlrott-Gymnasium and lecturer in astronomy as part of the physics teacher training programme at the university of Wuppertal, has been studying this wonderful object for many years and now wants to bring it back to Wuppertal together with physicist Johannes Grebe-Ellis and historian Sabrina Engert. And the chances are good.

A carpenter's work with astronomical content

All that is known about Heinrich Aeuer today is that he ran a carpentry business between Elberfeld and Barmen, says Winkhaus. As a teenager, he had contact with astronomy through his confirmation classes and even wanted to study it, but his father forced him to take over his father's carpentry business. "That's how these dual interests came about," explains the graduate physicist, "i.e. carpentry work, but with astronomical content.

That is the essence of this tabletop planetarium." The planetarium is the size of about four school desks placed side by side and shows everything that can be experienced in astronomy in the sky. "So the movement of the planets, the phases of the moon, the measurement of time, both the daily rotation of the earth, which makes up our time of day, with solar time and sidereal time. You can also see the months. It all works via a crank mechanism. So if you turn a crank, everything starts to move, just like in reality," says Winkhaus, describing the fascinating object. You can also switch on several gears to speed up processes for demonstration purposes. Before the much later introduction of projection planetariums, you could already see everything on this tabletop planetarium.

Founding of the school in 1830 and purchase of the table planetarium

The Höhere Bürger- und Realschule Elberfeld, forerunner of today's Carl-Fuhlrott-Gymnasium, was founded in 1830 and located in Herzogstraße. The school's founding phase also included the purchase of the tabletop planetarium for a considerable sum, even back then. "Back then, that was in thalers. It was a worker's two-year salary, which today would be estimated at around eighty to one hundred and fifty thousand euros. I don't think he built the planetarium purely for commercial reasons, because he also wrote two books, which are available in the city archives. You can see his enthusiasm for astronomy and his obsession with detail." Winkhaus was even able to find contracts for the maintenance work carried out by Aeuer himself in the early years in the school's own archive. In 1900, the school moved again, this time to Robert-Daum-Platz, where the Laurentius School is located today. There, the tabletop planetarium stood in front of the assembly hall in a glass case; Winkhaus assumes that it was no longer fully functional at the time. What is interesting in this context is the fact that interest in astronomy was so great at both school locations that an additional observatory was built at the time. However, the observatory at Laurentius School, which was destroyed in the war, was never rebuilt.

1903 - Foundation of the Deutsches Museum in Munich

"In 1903, the Deutsches Museum in Munich was founded by Kaiser Wilhelm. The founding father was Oskar von Miller, who had the idea of establishing a hands-on museum as the first museum in the world. The exhibits should be hands-on," says Winkhaus. This completely modern, new museum concept is now one of the largest hands-on museums in the world. "Among the early supporters of the Deutsches Museum were the Wuppertal chemist Carl Duisberg and the Wuppertal-based company Bayer. Although the magnificent modern building was now finished, it had to be filled with life because there was simply a lack of exhibits. "And so the museum operators started looking for interesting objects. Duisberg from Wuppertal remembered the beautiful tabletop planetarium. And he sort of talked the then director Börner out of it, as he didn't really want to give it away because he was interested in astronomy himself," explains Winkhaus. He therefore loaned the tabletop planetarium to the museum and drew up a contract to this effect. "It was then on display in the planetarium exhibition until 1990," he continues. "But then the museum concept was completely changed and the planetarium exhibition no longer exists, so all the exhibits, including the tabletop planetarium, were moved to the basement." As part of a work placement, Winkhaus then commissioned two pupils from his grammar school to produce documentation on the tabletop planetarium, which is now available. It also contains the decoding of all the astronomical functions. And with that, the idea of bringing the object back to Wuppertal matured.

Cooperation between Bergische Uni and Carl-Fuhlrott-Gymnasium

The three protagonists mentioned are hoping for further support from students and pupils and are planning a potential return of the planetarium for the year 2030. "The school was founded in 1830," explains Winkhaus, "which means that in 2030 we will be celebrating the 200th year of our existence. So it would be wonderful if we could present an exhibit for this anniversary date, even in a restored form, that dates back to the first days of the school's history." Five years of planning is also a good amount of time to be able to realise everything. Of course, he is particularly grateful for the support of his fellow campaigners. "A school is working together with the history of science and technology and physics at the university. This also emphasises our seriousness about bringing the planetarium back to Wuppertal and raising the necessary funding, as the instrument also needs to be restored."

Rich detail and prophetic interpretation

The Elberfeld tabletop planetarium has a wealth of details to offer, which are also spectacular. Winkhaus comments: "This Heinrich Aeuer was an incredible guy. I'm an astronomer myself and I'm completely amazed at the detail with which he designed this tabletop planetarium. These are not just the most important celestial functions. So when you look at it you immediately see the following: a Copernican planetarium, the planets move around the sun. If you now take a closer look at the planets, you can see that there are a few more than there are today. Ceres and Vesta, for example, are so-called minor planets that were still part of the planetary system back then because they are objects that move around the sun." It should be noted that reasonably good telescopes had only existed since 1780, but Aeuer had already started building his planetarium in 1820.

"If you then look at the side of the tabletop planetarium, you can see a celestial globe and an earth globe, both of which rotate, so that you can basically understand the different time systems that are used by rotating these globes. Then there is a small sphere at one point that you can only see half of, which is also only painted black and white. This is the current phase of the moon for that day, which you can turn."

Aeuer then added a very special, spectacular detail, which really left Winkhaus speechless. "The planet Uranus was discovered by Wilhelm Herschel in 1781, just 40 years before Aeuer started building the planetarium. He gave the planet a ring, similar to that of the planet Saturn. But this ring is perpendicular to the orbit, we say to the ecliptic, while Saturn appears parallel or slightly offset in the sky. This is a rather unusual position for such a ring. The remarkable thing is that this ring was only discovered by the Voyage probe at the end of the 1970s. Firstly, that Uranus has rings at all and secondly, that they have such an unusual position in relation to the ecliptic. So how does this carpenter know that?"

Winkhaus finds the answer in one of Aeuer's books. "He says that Wilhelm Herschel saw little stars twinkling next to Uranus, stars that disappear and reappear. And Heinrich Aeuer now concludes from this that Uranus may also have rings that cover the stars from time to time. And from the blinking of these stars, he now concludes that they have an unusual position in relation to the ecliptic. That was his assumption and that's why he added it, but also noted that if he was wrong, the rings could be removed again. Today we know that the carpenter from Wuppertal was right."

Kick-off event for the tabletop planetarium in the city library

The first launch event to reintroduce the Elberfeld tabletop planetarium to the people of Wuppertal is scheduled for 7 October in the city library. At 6.30 pm, Winkhaus will decode the astronomical, spectacular and unique aspects of this planetarium. Visitors will learn what used to happen in their city. Sabrina Engert concludes by emphasising once again: "People can expect a really great presentation that will captivate them. I have already had the pleasure of hearing Michael Winkhaus speak in my seminar and my students were absolutely thrilled. He puts his heart and soul into it and is able to explain the topic in a way that even laypeople can understand. Astronomy enthusiasts as well as historians and city lovers will get their money's worth."

Uwe Blass

Michael Winkhaus is a physics teacher, head of the student astronomy laboratory at Carl-Fuhlrott-Gymnasium and a lecturer in astronomy as part of the physics teacher training programme at the university of Wuppertal.
Sabrina Engert is a research assistant and doctoral candidate in the History of Science and Technology at the School of Humanities and Cultural Studies at the University of Wuppertal and the Interdisciplinary Centre for Science and Technology Studies.
Johannes Grebe-Ellis is a professor of physics and its didactics in the school of mathematics and natural sciences at the University of Wuppertal