Page - 137 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

137The 1761 Transit of Venus and Hell’s Transition to Fame Hell’s Vardø trip was regarded in the eighteenth century as being almost as exotic, and certainly no less scientifically important, as those undertaken by James Cook (1728–79) to Tahiti in 1769 or by Chappe d’Auteroche to Tobolsk in 1761 and Baja California in 1769. For over a hundred years, his sets of data from Vardø featured prominently in debates about the distances of the solar system. The expedition and its scientific results, therefore, figure quite prominently in the scholarship. By contrast, the place of Vienna and Hell in 1761 is more of a footnote in the master narrative. Doing justice to them is not an exercise of merely antiquarian or self-serving interest, but indispensable to the argument of this book about the intertwining of personal agency in the local, regional, and transnational spaces where Hell exerted his talents. Before providing an account of astronomical activity in the Habsburg terri- tories during and in the aftermath of the 1761 transit, some technicalities need to be considered. The astronomical unit to be obtained from the Venus transit observations was based on the so-called parallax: the difference in the appar- ent position of an object against a background when viewed from different angles. The observation of the passage of the tiny disc of Venus, when viewed from different positions against the background of the Sun as various astrono- mers spread themselves over the Earth, made it possible to determine a parallax—called the solar parallax—provided that the distance between vari- ous observation sites was accurately measured, and the observers at each loca- tion properly kept the time. In sum, two sets of data were necessary: first, the geographical position of each observer, and second, the exact divergence of Venus’s path in front of the Sun as seen from the various stations. The figure of the solar parallax was really just a compressed, internationally acceptable way of expressing the distance between the Earth and the Sun, without having to choose between English, French, or various German miles, the Russian verst, the French toise, or (later) the kilometer. Determination of the Astronomical Unit,” Science and Education 18 (2007): 581–92; on Australia, R.J. Bray, “Australia and the Transit of Venus,” Proceedings of the Astronomical Soci- ety of Australia 4 (1980): 114–20; on the Dutch East Indies, Robert H. van Gent, “Observations of the 1761 and 1769 Transits of Venus from Batavia (East Indies),” in Kurtz, Proceedings, 67–73; on Ireland, C. John Butler, “Observations of Planetary Transits Made in Ireland in the 18th Century and the Development of Astronomy in Ireland,” in Kurtz, Proceedings, 87–99; on France, Harry Woolf, Les astronomes françaises, le passage de Vénus et la diffusion de la science au xviiie siècle (Paris: Université de Paris, 1962); Jean-Claude Pecker, “Jérôme de Lalande and International Cooperation,” in Brosche et al., Message of the Angles, 52–62; Suzanne Débar- bat, “Venus Transits: A French View,” in Kurtz, Proceedings, 41–51; on Scandinavia, Per Pippin Aspaas, “Nordiske amatørastronomers bidrag i forbindelse med venuspassasjene 1761 og 1769,” in Mellom pasjon og profesjonalisme: Dilettantkulturer i skandinavisk kunst og vitenskap, ed. Marie-Theres Federhofer and Hanna Hodacs (Trondheim: Tapir, 2011), 103–27.