Mariners Astrolabe antique gold

Mariners Astrolabe antique gold

In the 1400s, the mariner's astrolabe 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. 

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.