Ferdinand Augustin Hallerstein

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).

Hallerstein was born on 27 August 1703 in Ljubljana[2][3][4] (in older sources in Mengeš, incorrectly citing the date as 18 August 1703),[2][5] Carniola (then part of the Habsburg monarchy, now in Slovenia)[6] as a member of the Hungarian branch of the famous Haller von Hallerstein family from Nuremberg, Germany.

[7] He spent his youth in Mengeš, where his family owned Ravbar Castle, and studied at the Jesuit college in Ljubljana.

It confirms all the calculations of one of his predecessors, Father Amiot and affords proof of the progressive increase of the Chinese population.

In recent years he has attracted the attention of Chinese historians as the creator of the most intriguing astronomic instrument at the old Beijing observatory, the spherical astrolabe, a "celestial globe".