In order to determine the difference in longitude between Tycho Brahe's observatory on the island of Hven and the new observatory in Paris, the French astronomer Jean Picard travelled to Copenhagen with the most accurate equipment to measure that difference. The mission was a success, he determined the difference that was only 10 minutes wrong compared to a modern value and he brought with him back to Paris Ole Roemer. In this paper I analyze Picard scientific achiements and methods while on Hven and at the Round Tower in Copenhagen.
Jean Picard Et Les Débuts De L'astronomie De Précision Au Xviie siècle, 1987, p. 175-203
Jean Picard, Ole Roemer, difference of longitudes
Main Research Area:
Jean Picard et les débuts de l'astronomie de précision au XVII<sup>e</sup> siècle, 1987