German astronomer, astrologer and published author, the astrologer of the court of Emperor Charles V. He was a diplomat, a humanist, politician, banker, merchant, historian and data collector, producing horoscopes of nobility. Rantzau’s interests focused on astro-medicine, fundamental principles of astrology and astrobiographical studies. His books included a collection of horoscopes of emperors and high aristocracy, a collection of 87 horoscopes, 1585, one on astro-medicine and one on the basics of astrology.
Rantzau was the son of one of the generals of King Christian III of Denmark. He established an extensive library which was partly burned down during later plundering by Polish and Czech mercenaries. Obviously precocious, he was sent abroad at age 12 to study at the Protestant U. in Wittenberg in Germany, where his professor of Greek was the astrologer Phillipp Melanchthon, a friend of the reformer Martin Luther. When he returned to Denmark, he was employed in the service of King Frederic II and became the governor of the duchies on the border between Denmark and Germany, where he was soon caught between quarrels with the dukes. Tycho Brahe also was troubled after the death of his protector, Frederick II. The political scene in Den mark was changing, in part as the result of the religious struggle in Europe, and Rantzau had to flee to Prague, where he died 12/31/1598, Breitenbrunn, Germany. (Paul Mahler Dam gives his death in 1601, Prague.)
Link to Wikipedia biography