Mariner's astrolabe

This article is about the Mariner's astrolabe. For the Planispheric astrolabe, see Astrolabe.

Three Mariner's Astrolabes in the Museum of the Forte da Ponta da Bandeira; Lagos, Portugal

The mariner's astrolabe, also called sea astrolabe, was an inclinometer used to determine the latitude of a ship at sea by measuring the sun's noon altitude (declination) or the meridian altitude of a star of known declination. Not an astrolabe proper, the mariner's astrolabe was rather a graduated circle with an alidade used to measure vertical angles. They were designed to allow for their use on boats in rough water and/or in heavy winds,[1] which astrolabes are ill-equipped to handle. It was invented by the Portuguese people, a nation known for its maritime prowess that dominated the sea for multiple centuries. In the sixteenth century, the instrument was also called a ring.[2]

  1. ^ "What is a mariner's astrolabe?".
  2. ^ Cite error: The named reference waters was invoked but never defined (see the help page).