Tycho's observatory island of Hven. 17th-century map of the island of Hven, the site of the Uraniborg observatory of Danish astronomer Tycho Brahe (1546-1601). North is at bottom. Named for the Greek muse of astronomy, the Uraniborg observatory (near centre) was used to make the most accurate naked-eye measurements yet made of the position of the stars. It was built between 1576 and 1580. Hven is a small island (7.5 square kilometres) in the Oresund strait between Denmark and Sweden. This page is from the 1603 edition of Tycho's 'De Mundi Aetherei Recentioribus Phaenomenis Liber Secundus', originally published in 1588.