The octant has an ebony frame and limb with a brass index arm, fittings, and a brass stop for the index arm. It also has inlaid ivory plates on the crossbar and on the back of the frame. There is no tangent screw and the clamping screw is located on the back of the index arm. The octant has three index shades, two red and one green. Index-glass adjustment is made by a screw and on the horizon glass by a lever, wing nut, and a milled clamping screw. The sight vane has two pinholes and a swivelling shutter. A brass-capped screwdriver is fitted in the crossbar. The octant is contained in a stepped mahogany box, which has been repaired and painted white on the inside.

The instrument has an inlaid ivory scale from -2° to 100° by 20 arcminutes, measuring to 92°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.