Like many of his peers in the 16th century, Duke Ulrich of Mecklenburg-Güstrow in North-Eastern Germany was a great patron of the arts and sciences. Instruments, clocks and automata were amongst his most-priced possessions.

Among the artisans working at his court features Peter Jachenow. The Schwerin clockmaker and instrument-maker was especially valued for his odometers, which were popular not only with Duke Ulrich, but also with King Frederick II of Denmark and Tycho Brahe, with whom the Duke was in close contact. From about 1588 Jachenow became a frequent visitor of Tycho’s, whose carriage he fitted with an odometer that recorded distances to the striking of bells. Tycho was enchanted with his acquisition and recommended Jachenow to Thaddaeus Hagecius, astronomer and doctor to Emperor Rudolf II.

This paper will attempt to shed some light on this now little known instrument maker who was at his time highly regarded at the courts of Europe.