Page - 299 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

299Observing Venus and Debating the Parallax Father Hell had all the time in the world to adjust his observation (not upon the calculation […], but upon the numerous observations of other observers who had published their reports earnestly). Father Hell ex- cused himself by stating that the observation was not his own property and that he could not share it with others, nor make it public, until he had paid tribute to the king of Denmark, who had asked for Father Hell from Empress Maria Theresa in order that he should make this observa- tion in his estates. However, an astronomical observation is not a state secret, and you hardly need nine months to print the couple of lines re- quired to explain the entire observation.142 When in the 1820s Encke took upon himself the task of re-calculating the solar parallax on the basis of the observations of the 1760s, he was thus liable to a certain degree of skepticism toward the datasets from Vardø. Encke first issued a calculation of the solar parallax based on all observa- tions from 1761. This yielded a parallax of 8.490525″,143 a figure in perfect agree- ment with Lalande’s position. When he proceeded to investigate the issue on the basis of observations from 1769, Encke clearly had no doubts that the late Jesuit could have been capable of manipulating his datasets. As he saw it, Hell’s calculations of the solar parallax were of no value, his abilities as an observer more than questionable, and his excuses for his report’s late arrival “utterly futile.”144 Accordingly, in a treatise on the solar parallax based on the ob- servations from 1769, Encke found on the basis of all observations—Hell’s excluded—a parallax of 8.5776″ ±0.037″.145 When he included the data of the Jesuit in the calculation, the result was 8.60″. As Encke himself conceded, that difference was “well within the limits of likely error.”146 However, given that his earlier investigation based on the 1761 observations had yielded 8.49″, Encke 142 Franz Xaver von Zach, Correspondance astronomique, géographique, hydrographique et statistique du Baron de Zach (Genoa: A. Ponthenier, 1818), 1:176. 143 Encke’s Die Entfernung der Sonne von der Erde aus dem Venusdurchgänge von 1761 hergeleit- et (Gotha: Becher, 1822) could not be consulted. The parallax value is, however, given in Verdun, “Die Bestimmung der Sonnen-Parallaxe.” 144 Johann Franz Encke, Der Venusdurchgang von 1769 als Fortsetzung der Abhandlung über die Entfernung der Sonne von der Erde (Gotha: Becker, 1822), passim (quotation on 18). 145 Encke, Der Venusdurchgang von 1769, 109. 146 Johann Franz Encke, “Über den Venusdurchgang von 1769,” Abhandlungen der Königli- chen Akademie der Wissenschaften zu Berlin: Mathematische Klasse (1835; published 1837): 295–309, here 302: “The inclusion of the Vardøhusian observation yielded a parallax of 8.60 arc seconds, whereas all the other observations, the Vardøhusian excepted, yielded 8.58, a difference [etc.].”