Representing sun and stars
The rete of an astrolabe is the decoratively cut plate which rotates to represent the apparent motion of sun and stars. A typical astrolabe has a fine network of star pointers and an offset circle for the sun's annual circuit through the zodiac [1].
The museum's smallest astrolabe does not have a complete zodiac circle [2]. The restricted size of the projection means it has been folded over on itself to create an arc. Although [3] has a zodiac circle and a few stars, its simplified rete reflects the different purpose of the instrument: underlying the rete is a terrestrial planisphere rather than a celestial grid.