Werner Landgraf
He also developed a method of eliminating systematic errors in positioning brighter comets that resulted in a more accurate prediction of the Halley's Comet. A recalculation of the path of Halley's comet to 2317 BC confirmed that the Greeks had already seen the comet on 466 B.C.
He discovered seven minor planets including 3683 Baumann, 4378 Voigt (named after Hans-Heinrich Voigt), 9938 Kretlow and 4349 Tibúrcio at ESO's La Silla Observatory in northern Chile.
C/1760 A1
Messier came up against opposition from Navy astronomer Joseph Nicholas Delisle, who had employed Messier from October 1751, because Delisle would not publish the discovery Messier had made. This was a continuation of the mistrust that had developed between Messier and Delisle because Delisle had been slow to publish work done by Messier in 1759; Messier had independently rediscovered Halley's Comet on 21 January 1759 but because Messier had doubted the correctness of Delisle's path, Delisle instructed Messier to continue observing the comet and refused to announce his discovery. Delisle apparently later changed his mind and announced the discovery on 1 April 1759, but other French astronomers discredited Delisle's claim, labelling the discovery an April Fools' joke. Delisle retired in 1760.