page_title: Orion-class battleship
section_title: Fire control
hierarchical_section_title: Orion-class battleship / Description / Fire control
caption_attribution_description: HMS Conqueror in line abreast, May 1917
context_page_description: The Orion-class battleships were a group of four dreadnought battleships built for the Royal Navy in the early 1910s. The first 13.5-inch-gunned battleships built for the RN, they were much larger than the preceding British dreadnoughts and were sometimes termed "super-dreadnoughts". The sister ships spent most of their careers assigned to the 2nd Battle Squadron of the Home and Grand Fleets, sometimes serving as flagships. Aside from participating in the failed attempt to intercept the German ships that had bombarded Scarborough, Hartlepool and Whitby in late 1914, the Battle of Jutland in May 1916 and the inconclusive Action of 19 August, their service during World War I generally consisted of routine patrols and training in the North Sea.
  The Orions were deemed obsolete by the end of the war in 1918 and were reduced to reserve the following year. Orion and Conqueror were sold for scrap in 1922 while Monarch was hulked for use as a stationary training ship. In late 1923, she was converted into a target ship and was sunk in early 1925. Thunderer served the longest, acting as a training ship from 1921 until she, too, was sold for scrap in late 1926.
context_section_description: The control positions for the main armament were located in the spotting tops at the head of the fore and mainmasts. Data from a nine-foot (2.7 m) Barr and Stroud coincidence rangefinder, located at each control position, was input into a Dumaresq mechanical computer and electrically transmitted to Vickers range clocks located in the transmitting station located beneath each position on the main deck, where it was converted into range and deflection data for use by the guns. The target's data was also graphically recorded on a plotting table to assist the gunnery officer in predicting the movement of the target. The turrets, transmitting stations, and control positions could be connected in almost any combination. As a back up, two turrets in each ship could take over if necessary.
  Thunderer was the second British dreadnought to be built with a gunnery director, albeit a prototype. This was mounted on the foremast, underneath the spotting top and electrically provided data to the turrets via pointers, which the turret crew were to follow. The director layer fired the guns simultaneously which aided in spotting the shell splashes and minimised the effects of the roll on the dispersion of the shells. While the exact dates of installation are uncertain, all four ships were equipped with a director by December 1915.
  Additional nine-foot rangefinders, protected by armoured hoods, were added for each gun turret in late 1914. Furthermore, the ships were fitted with Mark II or III Dreyer Fire-control Tables, in early 1914, in each transmission station. It combined the functions of the Dumaresq and the range clock.
caption: Conqueror at sea in line abreast formation, May 1917
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