C/1760 A1

The Great Comet of 1760 was first seen on 7 January 1760 by Abbe Chevalier at Lisbon. However, the perihelion of this comet had occurred on 17 December 1759. It was observed until 30 December by Charles Messier, who had first discovered 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 to within approximately 0.0682 astronomical unit (AU) or 6.34 million miles. This is the 11th closest approach by a comet of all time. It had a Right Ascension of 7 hours 57 minutes and had a declension rate of -17.6 degrees. 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.

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.

As of June 2008, the comet was about 216 AU from the Sun.