1. TRAINING IN LEIDEN

AN EAGER STUDENT IN PRACTICAL ASTRONOMY

MARGGRAFE came to Leiden with the firm intention to train himself in practical astronomy. But in the first few months, he had to adjust to normal life at the university, following lectures from JACOB GOLIUS and other Leiden professors. After all, he needed to win GOLIUS’s trust before he would be allowed to work at the observatory on his own. From these first months in Leiden two documents are preserved, one with mathematical notes from GOLIUS’s lectures, and another with mostly illegible notes (caused by crabbed handwriting) concerning astronomical problems and related calculations, in which various times the expression Lugdunum Batavorum (Latin for Leiden) can be distinguished, with dates ranging from 20 May to 24 December 1636. Despite the scratchy handwriting, it is clear that the notes relate mainly to positions of the planets in the zodiac, mostly theoretical in nature, but with a single entry on 17 November 1636 suggesting an observation of the Moon and the planet Jupiter. These notes may have to do with MARGGRAFE’s activities in preparing horoscopes for some of his fellow students.

Shortly after new year 1637, MARGGRAFE received the green light to use the Leiden Observatory and its instruments on his own. His Leiden observation notes reveal that he started his regular astronomical observations in early January 1637. It was a week in which it was so cold that all classes at the university had to be cancelled. But as a consequence of the frost, it were also days with a very bright sky. MARGGRAFE started in the early morning, observing some obvious phenomena. With the 6-foot Blaeu quadrant and a portable sextant he measured the altitude of a few stars, looked with the telescope at the Moon, witnessed the gibbous shape of Venus, and tried to find the satellites around Jupiter, one of which he indeed was able to discern. After sunrise, he used a telescope to look at the Sun, and probably to his surprise, on 18 January he found that there was a sunspot visible on the Sun’s surface. It seemed a good start, because MARGGRAFE returned that very evening for more measurements of stellar positions with the sextant and the large quadrant.