Bearing Plate with alidade

An ingenious extemporised bearing plate found on a French trawler. It consists of a water-tight bulkhead electric light fitting (brass) which has been fitted with gimbals, diameter 12.2" (31cm) and balanced so that its glass is horizontal. The flat glass is fitted with a spigot for an alidade and a paper compass card, graduated 0-180 degrees through E & W, is stuck to its underside. The alidade is of copper with fixed sights, one sight carries a slit; the other an open frame (thread missing).

Object Details

ID: ACO0712
Type: Bearing Plate with alidade
Display location: Not on display
Creator: Unknown
Date made: circa 1939 ?
Credit: National Maritime Museum, Greenwich, London, Admiralty Compass Observatory
Measurements: Overall: 190 mm; Diameter: 333 mm