Page - 139 - in Maximilian Hell (1720–92) - And the Ends of Jesuit Science in Enlightenment Europe

139The 1761 Transit of Venus and Hell’s Transition to Fame A B Venus Path seen from B Sun Path seen from A Earth Figure 4 The shift of Venus’s path from two sites of observation During a transit of Venus, the path of the planet on the disc of the Sun as seen from A and B would shift, altering the times of ingress and egress as well as the total duration of the transit (note that the degree of shift has been exaggerated here). Illustration and accompanying text by Truls Lynne Hansen Figure 5 From Hell’s manual Transitus Veneris per discum Solis Anni 1761 Upper left (fig. i.) shows the black spot of Venus at various stages during its transit in front of the solar disc. The crucial moments of contact with the limb of the Sun are clearly marked (the two pairs of contact at ingress and egress are tagged as R and S respectively). Lower left illustrates the use of a camera obscura, with which laymen equipped with fairly modest instrumentation could trace the transit on a sheet of paper. Digitized by the Department of Astrophysics, University of Vienna