page_title: Mariner's astrolabe
hierarchical_section_title: Mariner's astrolabe
caption_attribution_description: Astrolabes; Museum of the Forte da Ponta da Bandeira; Lagos, Portugal
context_page_description: 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 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, which astrolabes are ill-equipped to handle. In the sixteenth century, the instrument was also called a ring.
context_section_description: 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, which astrolabes are ill-equipped to handle.  In the sixteenth century, the instrument was also called a ring.
caption: Three Mariner's Astrolabes in the Museum of the Forte da Ponta da Bandeira; Lagos, Portugal
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