Historical comet observations in China

Chinese records of comets are the most extensive and accurate in existence from the ancient and medieval periods, and stretch back across three millennia. Records exist at least as far back as 613 BC, and records may have been kept for many centuries before this. There are continuous records all the way through to the nineteenth century, using substantially consistent methods throughout. Chinese data accuracy is unsurpassed in the ancient world and was not overtaken by Western accuracy until the fifteenth century or, in some respects, not until the twentieth century.

Comets were observed in great detail because of their astrological significance. However, these observations are now of great use to modern astronomers. Their accuracy is sufficient to allow the calculation of orbital elements, and modern astronomers have done this for many comets. Most notably, ancient orbits of Halley's Comet have been determined using Chinese records, a feat not possible solely from modern data due to a close approach of the comet to Earth in the ninth century. Such close approaches cause comet orbits to change abruptly, and ancient changes of this sort cannot be accurately modelled from the comet's present-day orbital data.