(Nuremberg, 1543 and Basel, 1566)
The density and quality of the data provided about the copies make this a fascinating reference work not only for scholars interested in the history of astronomy but especially for all those interested in printing in the early modern period. The census will also provide an almost inexhaustible mine of information concerning the spread of ideas, scholarly networks, book collecting, and library development from the 17th to 20th centuries.
As a young teacher in Graz in the 1590s, Johannes Kepler became fascinated with the pattern of conjunctions of Saturn and Jupiter (which occur approximately every 20 years) and the way they moved around the zodiac in an 800-year cycle. He had the opportunity to follow the beginning of a new 800-year cycle in 1603–04 and was astonished when a brilliant (super)nova appeared near Saturn, Jupiter, and Mars on 11 October 1604. The time of the birth of Jesus would have been near another of these conjunctions, two 800-year cycles earlier, and Kepler conjectured that a conjunction just beginning a series in the so-called fiery signs could have triggered the star of Bethlehem. He recorded his conjectures in De stella nova (1606) and then again, with more chronological detail, in De vero anno (1614), in the year in which University of Groningen was established.