Abstract

Danish astronomy in the first half of the seventeenth century reflected the enduring legacy of Tycho Brahe and was dominated by his former assistant Longomontanus. This paper focuses on his successor as professor of astronomy, Jørgen From or Georgius Frommius in the Latin version, who was also the second director of the Round Tower observatory in Copenhagen. Before becoming a professor, Frommius travelled to the Netherlands and other countries. The letters from his journey cast light on the training of a young astronomer at the time. He most likely was the first Dane to observe the heavens with a telescope. In the 1640s, he got involved in a controversy with the French astronomer and astrologist Jean Morin, and he later contributed to Pierre Gassendi’s pioneering biography of Tycho Brahe. Although Frommius died at the age of 46, his brief career as professor and astronomer is of interest to national as well as international history of science.