The armillary sphere is a set of rings nested one inside another; turn the rings to line up with a star and its position in the sky can be read off. The celestial globe is a sphere with the sky marked on it, used to show the heavens.
In the Western Han, Luoxia Hong improved or invented the armillary sphere in order to draw up the Taichu calendar, and used it to measure the equatorial positions of the lodges.
In the Eastern Han Zhang Heng drove a celestial globe with water flowing from a clepsydra, making the water-powered armillary, so that the globe turned on its own, carried by the flowing water.
In the Northern Song Su Song completed his water-driven astronomical clock tower, which put the armillary sphere, the celestial globe and the time-announcing gear in one building.
Armillary Spheres is the class in the chapter on Cosmos on the armillary sphere and the celestial globe: astronomical instruments that measured and showed the sky with linked rings and axes. Luoxia Hong of the Western Han made an armillary sphere to measure the positions of the lodges, Zhang Heng of the Eastern Han drove a celestial globe by water, and Su Song of the Northern Song built the water-driven tower that combined an armillary sphere, a celestial globe and a time-announcing device.
