An armillary sphere (variations are the spherical astrolable, armilla, or armil) is a 3-D model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of celestial longitude and latitude and other astronomically important features, such as the ecliptic. As such, it differs from a celestial globe, a smooth sphere whose principal purpose is to map the constellations.
An Equinoctial Armillary is a type of universal armillary sphere (works at any latitude), being a type of super-accurate sundial. The celestial sphere is represented by three metal bands, the thickest of which, the equinoctial hour-ring, lies along the celestial equator. The sundial measures time using the shadow cast by the central metal sphere, which represents the Earth. This sphere is on a spike known as a gnomon, aligned with the polar axis. As the Sun moves across the sky the shadow moves around the equinoctial ring, falling on the associated hour.
Perspective Research Centre 
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