The octant has an anodized brass plain-pattern fame and a wooden handle. The tangent screw and clamping screw are located on the back of the index arm. The octant has four shades, two green and two red, and three horizon shades, one green and two red. Index-glass adjustment is made by a screw and on the horizon glass by capstan screws. Attached to the octant is a magnifier on an 80mm swivelling arm as well as a threaded, non-adjustable telescope bracket. The telescope is 83 mm in length and has an erect image. The sight-tube is 80 mm in length and has a red shaded eyepiece. The octant is contained in a fitted wooden keystone box, with trade labels in the lid for Francis M. Moore, The High Street, Belfast (1854-1906), and S. Thaxter and Son, Boston, USA (1822-1916).

The instrument has a bronzed limb with an inlaid silver scale from -5° to 125° by 15 arcminute, measuring to 101°. The octant has a silver vernier measuring to 15 arcseconds, with zero at the right.