This astrolabe has only one tympanum. There is a rete and a degree scale on the limb. The tympanum is engraved on both sides with two different planispheric projections: a polar stereographic projection for latitude 43° (Pisa) on the front; and an equatorial stereographic projection on the back. The rete carries a rotating index. On the back of the astrolabe are a degree scale with a Tychonic scale, a zodiacal band, a calendar with the months in Latin and Greek, a sundial, a shadow square, and an alidade with sights. Provenance: Medici collections.