Octant

The octant has a mahogany frame and index arm with a boxwood limb, brass fittings and a brass stop for the index arm. An inlaid plate in the crossbar is now missing. There is no tangent screw and the clamping screw, which is broken, is on the back of the index arm. Index-glass adjustment is made by a screw and both horizon glasses by levers, wing nuts and thumbscrews for clamping. The sight vane and the back sight vane, as well as the socket shades, are missing. The octant is contained in a stepped oak box.

The instrument has a boxwood transversal scale from 0° to 90° by 20° and vice versa for the zenith arcminutes distance, measuring to 90°. The scale reads to 2 arcminutes by the fiducial edge at the end of the index arm.