The octant has an ebony frame and limb with a brass index arm and fittings. It also has an inlaid ivory plate on the crossbar. The tangent screw and clamping screw are on the back of the index arm. The octant has three socket shades, two red, and one green, as well as two horizon shades, one of which is red, and the other is missing. Index-glass adjustment is made by a screw, and on the horizon glass it is by a lever, wing nut and a milled clamping screw. The sight vane has two pinholes and a swivelling shutter. The octant is contained in a stepped oak box.

The instrument has an inlaid ivory scale from -2° to 98° by 20 arcminutes, measuring to 90°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.