EARLY ASTRONOMICAL OBSERVATIONS OF THE SOUTHERN HEAVENS

Why was GEORG MARGGRAFE so eager to observe the heavens in the Southern Hemisphere? After all, his sibling CHRISTIAN testified in 1687 that his brother GEORG possessed ‘a great desire of contemplating the southern stars’. What did he think he could achieve there? Was there so much astronomical knowledge to be gained at that point in time? In short, what was in that time the state of affairs concerning the astronomy of the southern sky?

Many southern stars were already known in antiquity. In the catalogue attributed to CLAUDIUS PTOLEMY (c.100–c.170) already more than 170 stars belonging to the southern celestial sphere are listed, most of them with positions not far below the equator. A celestial map of the southern sky, engraved by ALBRECHT DÜRER in 1515, shows what was known until the year 1598 (fig. 81).

Around the southern pole only a handful of stars were known. Most of the region there was empty space. Understandably, because stars located there are invisible for observers at European latitudes. In the late sixteenth century TYCHO BRAHE had included these southern stars in his star catalogue, but every astronomer knew that, compared to TYCHO’s own observations, these data of stars around the south pole had to be considered inaccurate.

This situation changed in 1598 when in Amsterdam a celestial globe was published by the publisher JODOCUS HONDIUS. On his globes information was processed collected during the so-called Eerste Scheepvaart (‘First nautical reconnaissance’), a voyage of Dutch navigators to the Indonesian archipelago performed during the years 1595-1598. This gathering of information about the southern stars was done at the request of the Amsterdam mathematician PETRUS PLANCIUS. He was the real auctor intelectualis behind Hondius’s globe publishing project. It was PLANCIUS, too, who arranged the 185 southern stars on HONDIUS’S globe (among which 13 were non-Ptolemaic) into 12 newly invented southern constellations. Most observations during the Eerste Scheepvaart were carried out by the skipper PIETER DIRCKSZ KEYSER, who unfortunately died before his return to the Netherlands. Therefore, it was his companion on the same ship, Frederick de Houtman, who brough the information back to Plancius.