Ferdinand Augustin Hallerstein

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Ferdinand Augustin Haller von Hallerstein (Slovene: Ferdinand Avguštin Haller von Hallerstein; 27 August 1703 – 29 October 1774), also known as August Allerstein or by his Chinese name Liu Songling (simplified Chinese: 刘松龄; traditional Chinese: 劉松齡; pinyin: Liú Sōnglíng), was a Jesuit missionary and astronomer from Carniola (then Habsburg monarchy, now Slovenia). He was active in 18th-century China and spent 35 years at the imperial court of the Qianlong Emperor as the head of the Imperial Astronomical Bureau and Board of Mathematics. He created an armillary sphere with rotating rings at the Beijing Observatory and was the first demographer in China who precisely calculated the exact number of Chinese population of the time (198,214,553). He also participated in Chinese cartography, serving concurrently as a missionary, "cultural ambassador" and mandarin between 1739 and 1774.