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'Gan De' (, fl. 4th century BC) was a Chinese astronomer/astrologer born in the State of Qi ^[1] also known as the 'Lord Gan' (Gan Gong). Along with Shi Shen, he is the first in history to compile a star catalogue, followed by the Greek Hipparchus who was the first in the Western tradition to create a star catalogue.
He wrote two books, the ''Treatise on Jupiter'' and the 8-volumes ''Treatise on Astronomical Astrology'' ^[2], both of which have been lost. It can be seen on the quotations under Shiji (volume 27) and Hanshu (volume 26), but was preserved mostly in the Treatise on Astrology of the Kaiyuan Era ^[3]. In 1973, a similar catalogue by him and Shi Shen was uncovered in Mawangdui and was arranged under the name of Divination of Five Planets, it records the motion of Jupiter, Saturn, Venus and other planets in their orbits between 246 BC and 177 BC.
He is reported to have seen one of the moons of Jupiter (possibly Ganymede) with his naked eye in 364 BC, long before Galileo Galilei's celebrated discovery of the same in 1610 (all four of the brightest moons are technically visible to the unaided eye, but in practice are normally hidden by the glare of Jupiter). By occluding Jupiter itself behind a high tree limb perpendicular to the satellites' orbital plane to prevent the planet's glare from obscuring them, one or more of the Galilean moons can be spotted in favorable conditions.

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Footnotes

1. Shiji 27 stated that he was from the State of Qi, however according to a commentary added by Xu Guang in the 4th century state that he was from the State of Lu, further citation from another work dated to the 5th century by Ruan Xiaoxu given an account that he was from the State of Chu.
2. also known as the Gan's Treatise on Stars.
3. Another 2 volumes preserved texts were attributed to him and Shi Shen and were incorporated to the Daoist Canon during the Song Dynasty, more commonly known as the Treatise on Stars of Gan and Shi. However, the book is generally not considered to be the more reliable than the Treatise on Astrology of the Kaiyuan Era, due to the anachronistic of name of places, etc. in the texts.

References

★ Biographies of Ancient Chinese Scientists Series One: Gan De, Du Shiran et al, , , Kexue Chubanshe, 1992, ISBN 7-03-002926-7

★ Discoveries and Studies on the Bamboo and Silk Texts, Ma Linghong, , , Shanghai Shudian Chubanshe, 2002, ISBN 7-80622-944-2

★ Great Lexicon on Chinese Arts of Necromancy, Gu Jianqing et al, , , Zhongshan University Press, 1991, ISBN 7-306-00313-5

★ X. Zezong, The Discovery of Jupiter's Satellite Made by Gan De 2000 years Before Galileo, ''Chinese Physics'' 2 (3) (1982): 664-667.

★ ''Sky and Telescope'', February , 1981.