The station pointer is made of brass and anodized brass and consists of a graduated circle and three arms, one of which is fixed at 0 degrees on the scale, while the other two can move around the circle and have fixing screws. The circle of this example has a diameter of 6 inches (152 mm) and a scale that runs from 0 to 360 degrees, with 0.5 degree subdivisions. It is contained in a fitted wooden case, which also holds a booklet, ‘On the Station Pointer and the Manner of Fixing a Ship’s Position by its Aid’ (2nd edition, 1903, reprinted 1916).

A station pointer is used for plotting a ship’s position from horizontal sextant angles taken between two or more objects or geographical features. To use it, the angles measured by the sextant are used to set the positions of the movable arms around the circle on the station pointer. This can then be placed on a chart to draw position lines from the features observed and so plot the ship’s position. This example was given to the NMM by the Navigation and Direction Division of the Admiralty.