Box (Pocket) Sextant

Generally referred to as a box, or drum, sextant, this is an exceptionally well made early 20th Century example. It is housed in a polished Brass drum case with a diameter of 7.8 cm (3"). It has an inlaid Silver scale with a range of 0 to 140 degrees. Major graduations are marked every 10 degrees - starting at zero and ending at 120 degrees. The scale is further divided into 1 degree minor graduations and 30 minute fine graduations. The vernier scale has marked graduations at 0, 10, 20 and 30 and fine graduations of 1 minute of arc.

Sightings are aided by a tiny pull-out telescope and a green glass sun shade. Adjustment of the Index Arm is via a knurled Brass knob and the reading is taken with the aid of a small magnifier that is mounted on a pivoting brass arm. The other small knurled brass knob is a tool for calibrating the horizon mirror.

A Box Sextant comes in two parts which screw together. The detailed images show how the two halves are screwed together when open and closed.

This type of sextant could have been used on lifeboats and would have been stored in a protective leather case.