A wooden nocturnal, an instrument used to determine time during the night, shown here with two closeup views of the intricate faces. This rare navigational device, one of only a few found in a shipwreck, is made up of three disks of wood, one of which is engraved with a calendar scale, compass degrees and constellations. Above the disks is a rotating pointer. To tell time at night, seamen would sight the relative positions of the North Star and another constellation on the nocturnal, then figure in the time of year. A plansiphere on the reverse face allowed the crew to calculate the various constellations viewable in the night sky using the previously determined time of night.
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