Octant consisting of a circular brass 45° sector fixed to a wooden base. The sector plate is inscribed with the sine scale. The rim displays the degree scale with cross-divisions (Tychonic scale). The alidade is complete with sights. There are two other sights on the rims of the plate at the ends of the sine scale. This type of instrument is depicted on the frame of Galileo's objective lens. Provenance: Medici collections.