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The ultimate benefit of the Chinese sky divisions was that when something new was spotted, the constellations they were said to be in were relatively small areas of the sky. Given the difficulty of accurately measuring the position of moving objects in early times, this was the next best way of giving a position. Astronomers of the 19th century were the first to fully appreciate these Chinese astronomical accounts, when investigations into the long-term motion of periodic comet 1P/Halley revealed several Chinese comets that were in the right area of the sky on the right date. The oldest account is from 240 BC! Other periodic comets to be successfully linked to Chinese comets include 109P/Swift-Tuttle and 153P/Ikeya-Zhang, with the former having first been seen in 69 BC!
My initial encounter with the valuable East Asian accounts came while researching my first books on comets and meteor showers during the mid-1970s. My initial haphazard methods first brought me to H. A. Newton’s early research into past appearances of the Leonid meteor shower. Newton’s papers in the 1863 and 1864 issues of the American Journal of Science revealed several observations made by the Chinese as early as the 10th century. Not long afterwards, I came across J. Williams’ 1871 book titled Observations of Comets From B. C. 611 to A. D. 1640 From the Chinese Annals. Both of these works seemed good attempts to systematically represent what the Chinese had observed, but they each fell short of being truly definitive works by using few sources, which were mostly second-hand accounts.
My next encounter with East Asian comet observations was an article that Ho Peng Yoke wrote in 1962 for the periodical Vistas in Astronomy. This catalog was more complete than Williams’ and typically used historical texts that were contemporary to the observations. He also took care in correcting apparent inaccuracies in some of the dates. Although Ho Peng Yoke also included accounts from Japanese and Korean historical texts, most of the Japanese accounts were not from contemporary sources. Nevertheless, the catalog became a reliable source that many researchers consulted when investigating ancient and medieval comets.