Navigation Instrument, Nocturnal, 17th Century

A nocturnal is a simple analog computer, made of two or more dials, that will provide the local time based on the time of year and a sighting of Polaris, the North Star, and one or more other stars. Knowing the time is important in piloting for calculating tides and some nocturnals incorporate tide charts for important ports. The earliest image presenting the use of a nocturnal is in a manuscript dated from the 12th century. Illustration from Ship and Ways of Other Days by Edward Keble Chatterton, 1913 (cropped and cleaned)

Restrictions Only for Ireland and United Kingdom

Analog Calculating Charts Chatterton Cleaned Cropped Dials Earliest Incorporate Keble Knowing Nocturnal Piloting Polaris Ports Presenting Provide Sighting Tide Tides Ways

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