| C/1760 A1 (Great Comet of 1760) | |
| Discoverer: | Abbe Chevalier Charles Messier |
| Discovery Date: | 7 January 1760 |
| Designations: | 1759 III |
| Epoch: | 17 December 1759 (JD 2363871.841) |
| Observation Arc: | 31 days |
| Perihelion: | 0.96576 AU |
| Eccentricity: | ~1.000 |
| Inclination: | 175.126° |
| Asc Node: | 83.553° |
| Arg Peri: | 301.727° |
| Magnitude: | 2.0 (1760 apparition) |
| Last P: | 17 December 1759 |
The Great Comet of 1760, also known as C/1760 A1 by its modern nomenclature, was first seen on 7 January 1760 by Abbe Chevalier at Lisbon.[1] Charles Messier also spotted the comet on 8 January 1760 in Paris, by the sword of Orion. The comet was his third discovery and the comet was the 51st to have a calculated orbit. Messier observed the comet for a total of 6 days.
It approached the Earth to within approximately 0.0682AU on January 8, 1760. This is the 17th closest approach by a comet of all time. Messier gave the comet a magnitude rating of 2.0, making it easily visible to the unaided eye. Messier also gave the comet an elongation angle of 140 degrees. Two days later, James Short also recorded his sighting of the comet while it was in the constellation Eridanus, noting that it moves about 2 degrees per day towards the west.
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 1765.
, the comet was about 216 AU from the Sun.[2]