The station pointer 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 4.75 inches (121 mm) and is made of brass with a silvered degree scale. The scale runs from 0 to 360 degrees, with 1 degree subdivisions, while verniers on the movable arms allow reading to 1 minute. It is contained in a fitted mahogany case (slightly damaged), which also holds extension pieces for each of the arms and a damaged magnifying glass. The trade label of ‘J.D. Potter, 31, Poultry, London’ is pasted inside the lid.

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. Station pointers are also used in surveying, in which case they have verniers attached to the movable arms to allow more accurate positioning, as this example does.

This station pointer once belonged to Captain M. H. H. Nelson, RN (died 1941).