This astrolabe is made of brass with the inscriptions, hour-lines, meridians and circles of altitude in silver; the rotating star map is made of brass, laminated with silver on the ecliptic and equatorial circles.
The globe is made of two hemispheres jointed by means of single coarse screw-thread. This instrument was never as popular as its flat counterpart, the planispheric astrolabe, and it is likely a few of them were ever made. This spherical astrolabe is the only complete example of its kind to survive. It was used to make astronomical calculations and is of Eastern Islamic origin. All the inscriptions are in Eastern Kufic Arabic and it is signed 'Work of Musa', Musa standing for an unknown instrument maker.