Johannes Praetorius
# Johannes Praetorius

Johannes Praetorius or Johann Richter (1537 – 27 October 1616) was a Bohemian German mathematician and astronomer.

## Life

Praetorius was born in Jáchymov, Bohemia. From 1557 he studied at the University of Wittenberg, and from 1562 to 1569 he lived in Nuremberg. His astronomical and mathematical instruments are kept at Germanisches Nationalmuseum in Nuremberg.

In 1571 he became Professor of mathematics (astronomy) at Wittenberg where he met Valentinus Otho and Joachim Rheticus. He died in Altdorf bei Nürnberg, aged about 79.

He taught Copernicus' theory of astronomy initially as a means of eliminating the equant from Ptolemy's account, and later moving to a proto-Tychonic system.

## Works

* De cometis, qui antea visi sunt, et de eo qui novissime mense Novembri apparuit, narratio 1578
* Problema, quod iubet ex quatuor rectis lineis datis quadrilaterum fieri, quod sit in circulo 1598
