Azimuthal Quadrant

John BirdXVIII century

Naval Museum

Naval Museum
Madrid, Spain

This instrument was used for both astronomical and navigational observations. In astronomy, it could measure the altitude of the stars, and in navigation, it could determine latitude and calculate the time.

It consists of a frame with 8 columns supported on 4 thick strips. On this framework there is a semicircular metal plate and 2 serrated circles that allow the quadrant to move. It has 2 ranges, one in the quarter circle and the other in the base of the support axis.

The quadrant arc has the inscription "J. Bird, London." John Bird (1709–76) was an astronomer and astronomical-instrument maker. He created impressive instruments for the observatories in Paris, Greenwich, Oxford (Radcliffe Observatory), and Cádiz.


  • Title: Azimuthal Quadrant
  • Creator: John Bird
  • Date Created: XVIII century
  • Location Created: London, England
  • Provenance: This quadrant was used by Jorge Juan and Antonio de Ulloa to measure the arc of the Earth's meridian in Peru (1736). After the expedition it was kept at the Royal College of Midshipmen. From there, it was moved to the Historical Military Museum, which donated it to the Naval Museum in 1940.
  • Type: Scientific Instrument
  • Original Source: Museo Naval Madrid.
  • Rights: Museo Naval, Madrid - All Rights Reserved
  • Medium: Brass and Wood
  • Height: 200cm
  • Diameter: 81cm(radio)

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