Johann Baptist Cysat

Who was Johann Baptist Cysat?

Johann Baptist Cysat was a Swiss Jesuit mathematician and astronomer, after whom the lunar crater Cysatus is named. Born in Lucerne, the eighth of 14 children, his father, Renward Cysat, had been active since 1575 in Lucerne as Kanzler and had published the first printed European book concerning Japan, called Von den Japanischen Inseln und Königreichen.

In 1604, Cysat joined the Jesuits and became a theology student in March 1611 in Ingolstadt. There he met Christoph Scheiner, whom he assisted in the latter’s observation of sunspots, whose discovery would later become a matter of dispute between Galileo and Scheiner.

In 1618, Cysat was named professor of mathematics at the University of Ingolstadt, succeeding Scheiner in this position, thereby allowing him to concern himself further with astronomical problems. Cysat became one of the first to make use of the newly developed telescope.