The octant has an ebony frame and limb with a black-lacquered brass index arm, fittings, and 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, two red and one green, and three horizon shades, two red and one green. Index-glass adjustment is made by a screw and on the horizon glass by capstan screws. The sight vane has two pinholes and a swivelling shutter. An ivory pencil head is fitted in the crossbar. Accompanying the instrument is an adjusting pin. The octant is contained in a mahogany keystone box.

The instrument has an inlaid ivory scale from -3° to 109° by 20 arcminutes, measuring to 99°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.