Details
The Mariners Astrolabe Geocoin is a replica of the 1400 mariner's astrolabe that was developed as the replacement for planispheric astrolabes used at sea and saw continued use until the 1700s.
It was a brass disk that was marked in degrees and had a spinning alidade. The distinctive large holes in the disk were to reduce its movement in light winds. It was designed to have a much simpler function and did not contain several moving disks which the planispheric astrolabe had that were difficult to utilize on a tossing ship.
Even though the mariner's astrolabe never fully replaced the quadrant (the quadrant was much too versatile) one of its biggest benefits is that you did not have to look directly at the sun to take a measurement like was needed with cross staffs and some quadrants.
The design of this coin:
The image of the navigator on the front of the Mariner's Astrolabe Geocoin™ shows how this tool was used when taking a reading from the sun. A real antique mariner's astrolabe would not have this raised edge. The two holes on the spinning alidade are small enough to get a fairly precise reading from sunlight, but are large enough to see through when taking a reading of the North Star, Polaris.
Additional Information
Barcode | N/A |
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Weight (kg) | 0.1030 |
Ships | Usually within 2 working days |
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