Page - 262 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

Chapter 6262 incorrect by 1.1 seconds, or 170 meters.12 It is important to note, however, that this remarkable accuracy resulted from a bit of luck as well as excellent obser- vational and calculating skills. With the data at hand, Hell might as well have opted for, say, 2h 4m 24s or 2h 4m 29s. It would still have been a very good deter- mination by eighteenth-century standards.13 For the determination of the latitude, Hell used a more unusual method, which merits some consideration. There was a widespread notion in contem- porary astronomy that the atmosphere in the north was thicker and the refrac- tion greater than in, for example, Paris, where the best tables of refraction had been made.14 Consequently, Hell was puzzled how to test the accuracy of his quadrants as well as the geographical position of his observatory. His choice was to use a selection of pairs of stars culminating in the same zenith distance, one in the north and the other in the south. In this way, any influence of a thicker atmosphere was eliminated: In the ordinary method, stars of no particular position are chosen—that is, some stars culminating at various zenith distances in the south, others in the north. That procedure requires that the refraction of the atmo- sphere is accurately determined and known to the observer […]. But this is not so in my method, [where] the effect of the refraction, however great or small that may be, [is ruled out].15 After a long series of observations, of which only an extract is given in the Ve- nus transit report, Hell concludes that the latitude of his observatory in Vardø was 70° 22′ 36″ north.16 12 We are indebted to Bjørn Geirr Harsson of the Norwegian Mapping and Cadastre Author- ity (Statens Kartverk) and Truls Lynne Hansen for this determination. 13 We rely on Truls Lynne Hansen for this assessment. 14 See, e.g., Gottfried Heinsius, “De refractionibus in oris septentrionalibus,” NcASIP (1758/59; published 1761): 412–44, where the author begins his discussion by stating that he finds it logical that the refraction be greater in the north than close to the equator, but concludes by affirming that this is not the case. Also, Hell admits that he was convinced that the re- fraction would be greater in Vardø than in Paris, and explains that his wish to examine the as-yet unexplored degree of refraction at the seventieth latitude was the main reason for him to spend the winter in Vardø (Hell, Observatio transitus Veneris […] 1769, 17): “This doubt, of the utmost importance, was certainly the most important among the motives leading me to spend the winter in Vardøhus.” 15 Hell, Observatio transitus Veneris […] 1769, 7–29; here 10–11. See also Hell’s article “Metho- dus astronomica Sine usu Quadrantis,” esp. 5. 16 Hell, Observatio transitus Veneris […] 1769, 17–29, esp. 27.