Michael Maestlin (September 30, 1550 - October 20, 1631) was a German astronomer and mathematician. He studied theology, mathematics, and astronomy/astrology and graduated as Magister in 1571. In 1576 he became a Lutheran deacon. In 1580 he became a Professor of mathematics, first at the University of Heidelberg, then at the University of Tubingen were he taught for 47 years. Among his students was Johannes Kepler. He was also one of the first to accept and teach the heliocentric Copernican view. He corresponded with Kepler frequently and played a sizable part in his adoption of the Copernican system. Galileo Galilei's adoption of heliocentrism was also attributed to Maestlin. He catalogued the Pleiades cluster in 1579. Eleven stars in the cluster were recorded by him, and possibly as many as fourteen were observed. The first known calculation of the (inverse) golden ratio as a decimal of,about 0.6180340, was written in 1597 by Maestlin in a letter to Kepler. He died in 1631 at the age of 81, This image has been colorized.