First Day Cover
首日封
Sobrescrito de 1.º Dia
ChinaAncient Astronomical Instruments (China - Denmark Joint Issue)
Date of Issue : 10 December 2011
(Left)
2-1 : Abridged Armilla
Jianyi (literally simplified instrument), or abridged armilla was invented by Chinese Yuan Dynasty astronomer Guo Shoujing (1231 - 1316) in 1279. As one of the significant astronomical instruments in Chinese history, the device overcame the problem of traditional armillary sphere's interwined rings, which created inconvenience for observation, and had a simpler construction featuring seperate rings perpendicular to each other. Mainly used to determine positions of celestial bodies by measuring their right ascension and declination, it was the world's most advanced astronomical instrument of its time.
(Right)
2-2 : Equatorial Armillary Sphere
The equatorial armillary sphere, constructed by Danish astronomer Tycho Brahe in 1585, was employed to observe the ecliptic co-ordinates and measure the longitude and latitude of the celestial bodies. As the inspiration of modern telescope's equatorial mount, the device was considered a milestone astronomical invention during the Renaissance in the West.
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