BornAmsterdam, the Netherlands, 10 June 1808
DiedLeiden, the Netherlands, 28 July 1872
Frederik Kaiser directed the Leiden Observatory from 1837 until his death in 1872. His contributions to Dutch astronomy included the foundation of a completely new observatory building in Leiden (in 1860, the first of its kind in the Netherlands) and the introduction of statistics and precision measurements in daily astronomical practice. Moreover, he was a gifted teacher and a skillful popularizer of astronomy.
Kaiser was the oldest boy of eight children born to Johann Wilhelm Keyser and Anna Sibella Liernur. His parents were immigrants from Nassau-Dietz in Germany. Kaiser’s father, a teacher of German, died in 1817 when Frederik was 8 years old. Kaiser was then raised by his uncle, Johan Frederik Keyser, a municipal employee and teacher of mathematics in Amsterdam. Keyser was a member of several learned societies and was known as a proficient amateur astronomer; he is said to have been the first to give a reasonable determination of the geographical coordinates of Amsterdam. In his young nephew Frederik, Keyser discovered a talent for mathematics and observational astronomy, and he decided to teach him the trade.
When Keyser himself died in 1823, the 15-year-old Kaiser took over his uncle’s job as a teacher of mathematics; with his uncle’s books and instruments, he further educated himself in the science of astronomy. By then, he had already published his first article, reporting his calculations of an occultation of the Pleiades by the Moon.
Kaiser owed much to his uncle’s colleagues for his university career. While the Dutch government could not provide Kaiser with a scholarship, Gerard Moll , director of the Utrecht University Observatory and a former pupil of Keyser, found a place for Kaiser as an observer at the Leiden Observatory, then a small construction on top of the academy building. His was the first professional post as observer in the country (1826). But to his disappointment, Kaiser found the observatory’s instruments old and broken, its structure unstable, and he did not get along well with its director, Pieter Johannes Uylenbroek, who was uninterested in practical astronomy. Kaiser borrowed a telescope and conducted better observations at home.
Kaiser earned his bachelor’s degree in mathematics and physics in 1831; the same year he married Aletta Rebecca Maria Barkey. The couple had one daughter and four sons, of whom one died in infancy. The third son, Pieter Jan Kaiser, later became an astronomer and succeeded his father as instrument controller for the Dutch Navy.
Better astronomical times were in store for Kaiser in 1835, when he received an honorary doctorate from the University of Leiden for his work on Halley’s comet (IP/Halley). This study included an improved prediction of the comet’s perihelion passage and a highly valued popular book on the subject. Kaiser’s recognition was followed by his appointment as lecturer and director of the observatory in 1837, extraordinary professor of astronomy (the first Dutch professoriate in astronomy) in 1840, and ordinary (full) professor in 1845.
Thus, Kaiser found himself in a position to make the most necessary changes to the observatory. He improved the construction of the building and purchased some new, high quality instruments, including a 6-in. Merz refractor. He also developed a master plan for what he called the “revival of Dutch astronomy.” Kaiser’s notion encompassed (1) promotion of the practice of astronomy at Leiden University by providing better education, (2) instruction of the general public by means of popular works, and (3) increasing international awareness of Dutch astronomical research through publication. Kaiser’s long-term efforts in this enterprise made him the key figure in the professionalization of nineteenth-century Dutch astronomy.
A series of fundamental observations was commenced in 1840. Kaiser concentrated on positional astronomy and continued this as the observatory’s policy throughout his life. He was the first to introduce statistical methods and precision measurement in Dutch astronomy, and wrote several works on the use of the micrometer and the determination of the “personal equation” of the observer.
Kaiser also became known for his lectures in popular astronomy and his many articles in popular magazines. His writings were often accompanied by complaints about the state of astronomy in the Netherlands, which helped to foster public opinion for the science of astronomy. In that context, Kaiser’s most appreciated work was De Sterrenhemel (1844–1845), an overview of astronomical theory and practice for the layman. It appeared in two volumes and four editions; parts of it were translated into German, Danish, and French.
Kaiser’s public persona was of considerable benefit in raising the funds for a new observatory. He had long planned a new, up-to-date building, based on models from Germany and the Pulkovo Observatory (Saint Petersburg, Russia). The Dutch government, however, was not eager to support his initiative. After many years of fruitless lobbying, a national fundraising campaign for Kaiser’s observatory was inaugurated. It was successful, and when the government provided the remaining funds, a fully equipped observatory building was finished (1860), the first of its kind in the Netherlands. Instruments included a state-of-the-art meridian circle by Pistor and Martins and a 7-in. Merz refractor. The staff was enlarged with an extra observer and some calculators.
Kaiser then initiated an extensive observational program. From 1864 to 1868, the fundamental parameters of some 180 stars were measured, followed by 202 stars for the Europäische Gradmessung (European Geodetic Survey). The results were published in 1868. Further work at the observatory was done on micrometer measurements of binary stars and planetary diameters, comets, and the rotation period of Mars. Between 1870 and 1876, the observatory participated in the observation of zones for the star catalog of the Astronomische Gesellschaft.
Kaiser had occupied astronomy-related functions as supervisor of the geodetic survey of the Dutch East Indies (1844–1857), as the founding director of the institute that controlled the calibration of instruments for the Dutch Navy (1858), and as a Dutch delegate and board member in the Europäische Gradmessung (1867). He was a member of the Royal Dutch Academy of Sciences, the Holland Society of Sciences, the Royal Astronomical Society, the Prussian Academy of Science, and the Astronomische Gesellschaft. In 1845, he was awarded the Dutch knighthood.
Kaiser’s health had always been precarious. After a severe illness in 1867, he had to abandon his nightly observational routine. The death of his wife in 1872 dealt him a second blow, from which he did not recover. Kaiser was succeeded as director of the observatory by Hendrik van de Sande Bakhuyzen .
Many a scientist of the next generation was stimulated by Kaiser’s lectures. Among his students we find the astronomers Van de Sande Bakhuyzen, Martin Hoek , and Jean Abraham Chretien Oudemans, who completed their doctoral research at Leiden Observatory. Also inspired by Kaiser’s teachings were Hendrik Lorentz , Johannes Bosscha (later director of the Delft Polytechnical Institute), and chemist Johannes Diderik van der Waals. Thus, Kaiser initiated the dissemination of a new level of precision in Dutch science.
Craters on the Moon and Mars are named for Kaiser.
His papers may be found at the Leiden Observatory and Leiden University Library, the Archief van de Rijkscommissie voor Geodesie (Delft), and the Instituut voor Maritieme Historie (the Hague).
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