The octant has an ebony frame and limb with a brass index arm, fittings and 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 index shades, two red and one green. Index-glass adjustment is made by a screw and on the horizon glass by a square-headed screw, a detached key, a lever, worm gear and a milled clamping screw. The sight vane has two pinholes and a swivelling shutter. An ivory pencil head is fitted in the crossbar and a milled adjusting key accompanies the instrument. The octant is contained in a mahogany keystone box.

The instrument has an inlaid ivory scale from -3° to 108° by 20 arcminutes, measuring to 92°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.