Octant

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An octant is a navigational instrument used for measuring angles necessary for determining a ship's position at sea. This wooden example was made around 1760, probably by John Urings, a ship-chandler based in London's Fenchurch Street between 1735 and 1771.

The 16-inch radius mahogany-frame octant has a foresight and backsight with brass fitments. There is an ivory plate stamped 'I. URINGS. Fecit. LONDON.' The inset boxwood scale is divided to 20 minutes, and by transversals to 2 minutes of arc.

An octant is so-called because the scale is one-eighth of a circle, although it can measure 90 degrees using the mirror on the top of the radial arm.

Record details

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• Online ID: 000-100-104-301-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1987.150
• Date: Around 1760
  c. 1760
  
• Material: Mahogany, brass, ivory. Inscription: I. URINGS. Fecit. LONDON.
  
• Dimensions: 470 mm x 390 mm x 90 mm
  
• What:
• Subject:
• Who: John Urings, London (Maker)
  The Leith Nautical College Collection
  
• Where: England, London
  
• Event:
• Description: Sixteen inch octant with foresight and backsight in mahogany with brass fitments, made by John Urings of London about 1760
  
• References:
  • For a description of the octant and its use, see Turner, G. L'E. Antique Scientific Instruments. Poole: 1980. p 34; Bennett, J.A. The Divided Circle: A history of instruments for astronomy, navigation and surveying. Oxford: 1987. p 132-4 
  • For Urings, see Clifton, Gloria, Directory of British Scientific Instrument Makers 1550-1851. London: 1995, p 285 
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