Francesco Bianchini’s Discovery of the Venus Markings. Strategies of Evidence and the Foundation of Knowledge in the Early Modern Astronomical Community

Francesco Bianchini’s treatise Hesperi et phosphori nova phaenomena (1728) was the first book to be published on telescopic observations of Venus. The present article examines the various strategies that gave Bianchini’s new discoveries their evidential force. Six different strategies of providing evidence come to the fore: the argument of technical and instrumental superiority; the proof of skill in seeing and drawing; the visualisation in images and models; the involvement of eyewitnesses; the exchange within a European scientific network; and the development of a nomenclature for the Venus markings. It will become clear that Bianchini’s publication - despite his inaccurate results - owed its considerable success to the effect of these principles. For a century and a half, it was considered the most important reference for the study of the planet Venus.