In 1621, who built a machine involved in Johannes Kepler's calculations of the orbit of the Moon?

Wilhelm Schickard (22 April 1592 – 24 October 1635) was a German professor of Hebrew and Astronomy. In 1621, Schickard built a machine based on gears for doing simplified multiplications involved in Johannes Kepler's calculations of the orbit of the Moon. In 1623 and 1624, in two letters that he sent to Kepler, he reported his design and construction of what he referred to as an “arithmeticum organum” that he has invented, but which would later be described as a Rechenuhr (calculating clock).

The machine was designed to assist in all the four basic functions of arithmetic (addition, subtraction, multiplication and division). Amongst its uses, Schickard suggested it would help in the laborious task of calculating astronomical tables. The machine could add and subtract six-digit numbers, and indicated an overflow of this capacity by ringing a bell. The adding machine in the base was primarily provided to assist in the difficult task of adding or multiplying two multi-digit numbers.

Schickard's machine was the first of several designs of direct entry calculating machines in the 17th century (including the designs of Blaise Pascal, Tito Burattini, Samuel Morland and René Grillet). The Schickard machine was particularly notable for its integration of an ingenious system of rotated Napier's rods for multiplication with a first known design for an adding machine, operated by rotating knobs for input, and with a register of rotated numbers showing in windows for output.