Born Paris, France, 4 April 1688
Died Paris, France, 11 September 1768
Joseph-Nicolas Delisle was a teacher and observational astronomer noted for his work on comet prediction and transits. Delisle was the son of Claude Delisle, a historian, and Nicole-Charlotte Millet de la Croyère. Educated at the Collège Mazarin, he developed an early interest in astronomy. Joining the Académie royale des sciences formally in 1714 (as an associéto Giacomo Maraldi ), Delisle was eventually appointed to the chair of mathematics at the Collège royal in 1718. He married about 1725, but had no children.
Delisle’s regular observations with his own equipment began in 1721; in the same year, he received an invitation from Peter the Great to found an observatory in Russia. From 1725 to 1747 Delisle worked at Saint Petersburg, training numerous students. Some of them later performed cartographic work intended to serve as raw material for an accurate map of the whole of Russia. In order to improve geographical longitude data, Delisle collected and published a long series of observations of the Jovian satellites at Saint Petersburg. He was especially interested in the transits of Mercury, which he tried to use for accurate determinations of the solar parallax in lieuof the rarer transits of Venus. After his return to Paris in 1748, Delisle resumed his observing and teaching activities; among his students were Joseph de Lalande and Charles Messier .
Practical needs caused Delisle to improve Edmond Halley ’s planetary tables, to publish several predictions of impending solar eclipses and Mercury transits, and, most importantly, to develop an easy-to-use set of tables intended to aid in the recovery of Halley’s comet (IP/Halley), combining (approximate) orbital elements and an unknown date of perihelion passage. His method, published in 1757 and for some time (e.g., by Heinrich Olbers ) associated with his name, is still of obvious benefit for the recovery of comets with known elliptical orbits but only one observed perihelion passage. Delisle’s last efforts were dedicated to the preparations for the Venus transit of 1761, helping to establish worldwide cooperation for observations of this event.
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