Nicholas Kratzer (1487 - 1550) was a German mathematician, astronomer, and horologist (the study of time). Kratzer came to England in 1516 and established himself as part of the artistic and scientific circle around Sir Thomas More. He tutored More's children in mathematics and astronomy and His talents obtained him a court position as astronomer and clock maker to King Henry VIII. He also collaborated with Holbein on producing maps, and in return the artist produced a portrait of him in 1528 that now hangs in the Louvre. It depicts the craftsman surrounded by the tools of his trade. He died in 1550 at the age of 63.