Bell's Station Keeper

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Bell's Station Keeper, Pattern 494, was an optical device used in the Royal Navy for rough-and-ready estimate of ranges, useful to ensure one's own ship was at the correct distance from another.

It had a prism within which would ship an object 16 feet at 200 yards, or 40 feet at 2.5 cables. Presumably, there were common rules-of-thumb to apply to this angle which would facilitate a quick determination at common distances such as between columns or to the ship ahead.[Inference]

In a pinch, it could also be used to measure ranges in combat, such as for Torpedo Control purposes.[1]

See Also


  1. Handbook of Torpedo Control, 1916. pp. 59-62.


  • Admiralty, Gunnery Branch (1917). Handbook of Torpedo Control, 1916. C.B. 302. Copy No. 141 at The National Archives. ADM 186/381.