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 is located on the front of the index arm and the clamping screw is on the back. The octant has three index shades in red, orange, and green; these are possibly replacements. Index-glass adjustment is made by a screw, however, the mount is incomplete and the screw is a replacement. The horizon glass is adjusted by a lever, a milled screw and a worm gear. The sight vane has two pinholes and a swivelling shade in red. A pencil or screwdriver is missing from the crossbar. The octant is contained in a stepped oak box, marked inside the lid in ink: ‘G. C. 1838’ and illegible pencilled digits. In paint on the top of the lid are the initials ‘g. c.’.

The instrument has an inlaid ivory scale from -2° to 100° by 20 arcminutes, measuring to 91°. The octant has an ivory vernier measuring to 1 arcminute, with zero at the right.