While the nature of the instrument is as yet unclear, it appears to have been an instrument having the same applications as the armillary sphere. (51)
Wlodarczyk, "Observing with the Armillary Sphere," Journal for the History of Astronomy 18 (1987): 177, 182.
This gives the impression that the accuracy of Yahya's azimuth circle was that of a typical armillary sphere, like the very model used by him.
For the first number of Abstraction-Creation, Art Non-Figuratif in 1932, Calder prepared a statement to accompany a reproduction of Little Universe, an open wire orb resembling an armillary sphere
Although the sky rolls forward unassisted by hydrodynamic propulsion, about 2,000 years ago, during China's Later, or Eastern, Han dynasty (AD 23-220), a renowned and innovative astronomer, Zhang Heng, coupled a water clock with an armillary sphere to drive that instrument at the diurnal rate.
By the era of Zhang (AD 78-139), the armillary was fully developed, and the oldest surviving account of it is Zhang's Illustrated Commentary on the Armillary Sphere. His description details the rings and references fundamental positions in the sky.
Zhang's manuscript on the water-driven clock drive, Apparatus for Rotating an Armillary Sphere by Clepsydra Water, is now known only from quotations by later scholars, but they confirm that his armillary was designed to track the Seven Luminaries (Sun, Moon, and the five planets visible to the unaided eye), seasonally significant events, and the times of dawn and dusk, and to verify their proper coordination with the calendar.
The armillary sphere is an ancient astronomical device used to illustrate the old geocentric universe (the "world" in the parlance of the day), and is a most fascinating device, both in its historical roots and mechanically.
The term "armillary sphere" would literally denote a sphere made of rings (armillaries), but its usage has been to refer to the astronomical device, so I stick with that when I use the term.