Who was Frederik Kaiser?

Frederik Kaiser has been of great importance for the development and popularization of the dutch astronomy. When he started as an astronomer at the Leiden observatory, the building and its facilities were in a terrible state. But at the end of his life in 1872 he had managed to establish a beautiful modern building which housed many important astronomers. Kaiser had to fight his whole life to get these facilities to Leiden.

Frederik Kaiser was born on the 10th of June 1808 in Amsterdam. His father, who was born in Diets in Nassau, moved to Amsterdam at the end of the 18th century because of a war that was going on at that time in Nassau .At the age of 17 Kaiser lost his father. His uncle Johan Frederik Keyser who worked as a private teacher in math and astronomy took custody over Kaiser from that moment on. Kaiser couldn’t have wished for a better teacher since his uncle was one of the few Dutch astronomers who did astronomical research of importance and made actual observations. Keyser must have been very proud of his nephew since he was a very smart and talented boy. Young Kaiser was able to make an accurate calculation of the solar eclipse in Amsterdam in 1823.
Unfortunately his uncle died at the age of 46 when Frederik was just 15 years old.

Appointment to observant

Because of the influence of his uncle, Kaiser got a job as observant at the observatory in Leiden in 1826. Visiting foreign astrophysicists often visited the ‘old Keyser’. Among them was the English astrophysicist Edgeworth. Back in England, Edgeworth met with Gerard Moll, a professor of astronomy in Utrecht, the Netherlands. At this meeting they spoke of the young Kaiser. Edgeworth considered him a promising young talent, who should be in civil service.
Back in the Netherlands, Moll met with Kaiser, which led to Kaisers recommendation to the ‘administrator of the public education’, Van Ewijck, who inform the curators of the Leidse Hogeschool [sub-university level]. Kaiser was then appointed observer at the Leidse Sterrewacht. Around the same time, professor C. Ekama died, and was succeeded by lector Uylenbroek, who, like Ekama, had to monitor the astronomy department. Uylenbroek did not think Kaiser was the right man for the job, and insisted on watching his every move. This difficult relationship caused a lot of delays, as Kaiser, who was a nervous fellow by his very nature, did not feel free to do as he pleased.

The observatory was a rather neglected department at that time. It existed, but that was it. The most important instrument, the telescope, was unusable, for instance. This instrument was made by the Frisian (northern Dutch province) telescope builder Rienks, and was given to the observatory by King Willem I. However, Rienks was quite probably not as able a telescope maker as he was made out to be, so the observatory had a bad but very expensive telescope. The rest of the instruments was either old or severely damaged. The quality of the instruments was, in fact, so bad that Kaiser was forced to use his uncles instruments instead. The first eleven years, matters continued like this. Kaiser never really like to talk about this ‘useless’ period of his career.

Popularization of astronomy in the Netherlands

At the beginning of the nineteenth century, there was very little public interest in astronomy. The appearance of two comets in 1807 and 1811 changed this a little. In 1833 Kaiser published a translation of the book that Littrow wrote about a comet that was discovered in 1826. The book was meant to reassure the general public, because people were afraid the comet would come near the earth. The translation became very popular and the translator also got a bit of fame. In 1834, Kaiser published anther book, this time about the comet Halley, that would appear in 1835. In this book was an accurate calculation of the comet’s orbit and a prediction of its visibility, among other things. With this book Kaiser became really famous.

Of course, Kaiser couldn’t wait to observe the comet himself. This was not possible in the observatory however, so Kaiser borrowed a telescope from a befriended amateur astronomer. He put the telescope in his own house (running the risk of collapsing the roof) and even removed some roof tiles for this. From all around the country people came to Kaisers house to look at the comet, some of whom were influential people from The Hague. The fact that they had to look at the comet at Kaisers house with a borrowed telescope made them realise something had to be done about the alarming state the observatory was in.

For his efforts and achievements Kaiser was appointed doctor honoris causa in astronomy and mathematics, but the greatest reward was his appointment as lector in practical and theoretical astrophysics and director of the observatory in 1837. Kaiser about his apopintment: “From that day on the revival of astronomy in my homeland was my mission in life.” Kaiser started with the fulfillment of his mission by complaining to the government about the condition of the observatory.

Even though this gets him some new instruments, the poor location of the observatory remains unaltered and Kaiser has a hard time putting them properly in the rickety observatory. Even so, Kaiser does some commendable work on binaries.

During this period, education in astronomy also blooms. Kaiser did not only give lectures to students but also lectures about popular astronomy to members from other faculties and non-students. He put a lot of effort in making astronomy comprehensible for common people. He achieved this by using as little mathematics as possible in his lectures. Kaiser spoke and wrote with a lot of enthusiasm and humour and a tremendous passion for his profession.
In this period he published a lot of books, like ‘De Sterrenhemel’ (1844), and ‘Geschiedenis van de ontdekking der planeten’. Especially the first one made a big impression, to the point that it was even known abroad and readers started buying their own telescopes.

Lobbying for a new observatory
Kaiser realised that the improvements in the observatory were not enough to put astronomy in- and outside the Netherlands on the map. Whenever he could, he complained about the decayed state of the building, the unhealthy environment and the vibrations from the street and the bell tower that disrupted the observations. In 1853 Kaisers complaints were finally acknowledged. The Eerste and Tweede Kamer [the upper and lower houses of the Dutch parliament] discussed the idea of a new observatory, but refused to invest any money in the project. In response to this, the curator of the Leidsche Hogeschool, mister Gevers van Endegeest, called on the Dutch citizens to make a donation for the new observatory. The first ones to contribute were the students. The student associations as well as individual students contributed a lot. Professors also contributed a lot and it wasn’t long before all around the country commissions were formed to collect money. They collected 26,000 guilders in total, which was not enough by far (the estimated budget was 90,000 guilders), but now the government could no longer be passive. When the new minister of internal affairs, mister G. Simons (and a student of astronomer Moll) put a proper budget on the project there was finally some real progress. The budget was approved of by the Dutch parliament in 1857 (with the new minister of internal affairs A.G.a. van Rappard) but building the observatory outside the city would cost too much money, which meant a part of the botanical garden had to be sacrificed. This introduced a major conflict between Kaiser and the professor of biology, mister Suringar.
Kaiser observed in the new observatory from 1864 until 1872. In 1868 he published the first part of the records of the observations at the new observatory. Shortly thereafter, in 1871, he fell ill. The second and third part of the records is also by his hand, but he has never received the published version of the third one. Frederik Kaiser died at the 28th of July, 1872.


Kaiser is not entirely self-educated, because he learned a lot from his uncle and during his time in Leiden he also went to classes. However, he formed the education and research in practical astrophysics on his own accord. When he had just become the director he had to teach himself a lot about (practical) astrophysics, because the government wouldn’t fund a trip abroad to learn a thing or two.
Kaiser helped to achieve that astrophysics is no longer a subsidiary field, but become more esteemed than it had ever been before. The public appreciation of his work becomes apparent in the popularity of his books and lectures and the incredible willingness of the people to collect money for the new observatory. With an unbelievable drive and unstoppable enthusiasm, Kaiser conquered all the setbacks that he had to endure and achieved his life goal: the revival of astronomy in the Netherlands. With the help of some influential friends he managed to lift astronomy to a whole other level.

By: Sascha Zeegers