The octant has an ebony frame and limb with a brass index arm and fittings. It also has inlaid ivory plates on the crossbar and on the back of the frame. The tangent screw and clamping screw are on the back of the index arm. The octant has three socket shades, one in green,and two in red. Index-glass adjustment is made by a screw. On the horizon glass it is made by a lever, a milled screw and worm gear and on the back horizon glass by a lever, a milled screw and a nut screw. The sight vane has two pinholes and a swivelling shutter, whereas the back sight vane has one pinhole. An ivory-capped pencil is fitted in the crossbar. The octant is contained in a damaged stepped oak box, tarred on the outside and painted blue-green on the inside.

The instrument has an inlaid ivory scale from -3° to 100° by 20 arcminutes, measuring to 90°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.