Page - 158 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

Chapter 3158 very day after the event. Most observers therefore used observations of this eclipse as the basis for their longitude determination. Again, however, when observing the eclipse, a similar set of sources of error had to be accounted for: atmospheric disturbances during the eclipse, minute inaccuracies in time- keeping, resulting from sudden changes in temperature, the subjective dis- cernment and skill of the observer, and so on.60 meridian for temporary observatories in faraway places was liable to a certain degree of error. 60 “It is true that the method which M. Delisle has substituted [to the one of Halley] presup- poses that the difference of the meridian between two observatories is known. Every er- ror committed in the difference of meridians will affect the result that can be deduced from the observations”—the editors acknowledged in the Histoire de l’Académie Royale des Sciences pour l’année 1757 [1762], 85. Figure 6 The black drop effect as depicted by Daniel Melander Daniel Melander (later ennobled Melanderhielm [1726–1810]), professor of astronomy at Uppsala, included this illustration in his 1769 report “Uttydning på de Phænomener, hvilka åtfölja Planeten Veneris Passage genom Solen” (Interpre- tation of the phenomena that follow the transit of the planet Venus through the Sun). Melander’s figures 2, 3, and 4 show formations of Venus (V) during interior contact at ingress. Digitized by Per Pippin Aspaas