Mariner's astrolabe
Astrolabio náutico
- Date
- c. 1480-1500 · confidence medium
- Place
- Lisbon, Portugal
- Credited to
- Portuguese pilots and cosmographers (the mathematicians' board of John II)
- Field
- Movement
⚠️ Disputed: the sources disagree.
What it is
A simplified, heavy version of the astrolabe, reduced to a graduated ring with an alidade, for measuring the height of the Sun and stars aboard a moving ship. It enabled latitude to be computed in open sea far from land.
The earliest dated specimen is the one from the Esmeralda wreck (c. 1503, found in 2014 off Oman); literary sources place it in the 1480s though some push it to the 1490s.
What it led to
- latitude sailing on Atlantic and Indian Ocean routes
- solar declination tables in navigation manuals
- replacement by the Davis quadrant and the octant