Regiomontanus and Astrology

One biographer detected a decline in Regiomontanus' interest in astrology over the course of his life, and came close to asserting that he rejected it altogether. But more recent commentators have suggested that occasional expressions of scepticism about astrological prognostications reflect a disquiet about the procedural rigour of the art, not its underlying principles. It seems plausible that, like certain other astronomers, Regiomontanus concentrated his efforts on mathematical astronomy because he felt that astrology could not be placed on a sound footing until the celestial motions could be modelled accurately.

An early modern horoscope A Horoscope "He will be a Doctor" from the Astrolabium planum (Augsburg, 1488) of Johannes Engel (c.1453-1512), who is said to have been a student of Regiomontanus.

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In his youth, Regiomontanus cast horoscopes for famous patrons. His Tabulae directionum, completed during his time in Hungary, were designed for astrological use, and contained a discussion of the different ways of determining the astrological houses. The calendars for 1475-1531 which he printed at Nuremberg contained only a limited quantity of astrological information, namely the method of finding times for blood-letting according to the position of the moon; subsequent editors added a quantity of additional material. But perhaps the works most indicative of Regiomontanus' hopes for an empirically-sound astrology were his almanacs or ephemerides, produced first in Vienna for his own benefit, and printed for the years 1475-1506 in Nuremberg. Weather forecasts and observations were juxtaposed by Regiomontanus in his manuscript almanacs, and the form of the printed text enabled scholars to enter their own weather observations in order to likewise check astrological predictions; extant copies reveal that several did so. Regiomontanus did not live to produce the special commentary to the ephemerides which he promised would reveal what advantages these almanacs hold for the multifaceted activities of physicians, for human births and telling the future, for weather forecasting, for the start of employment, and for a host of other activities, although this lack was again rectified by subsequent editors. Nevertheless this announcement suggests that Regiomontanus was either as convinced of the validity and utility of astrology as his contemporaries, or willing to put aside his misgivings to achieve commercial success.

Recommended Reading

J. Bennett & D. Bertoloni Meli, Sphaera Mundi: Astronomy Books in the Whipple Museum 1478-1600, Cambridge 1994, pp. 14-15, 32-44, 65

E. Zinner, Leben und Wirken des Joh. Müller von Königsberg, Osnabrück 1968. Translated by E. Brown as Regiomontanus: His Life and Work, Amsterdam 1990

Full Bibliography