Mariner's quadrant (plumb-bob quarter circle)
Cuadrante náutico (cuarto de círculo con plomada)
- Date
- c. 1460 · confidence low
- Place
- Lisbon, Portugal
- Credited to
- Portuguese pilots in Prince Henry's circle
- Field
- Movement
⚠️ Disputed: the sources disagree.
What it is
A graduated quarter circle with two sights and a plumb line that measures the height of the Pole Star above the horizon. Cheaper and easier to use than the astrolabe, it served to find latitude on the African coast voyages.
Its first dated nautical use is the one recounted by Diogo Gomes around 1462; the land instrument is much older.
What it led to
- latitude from the Pole Star's altitude on the African voyages
- solar declination tables for navigation
- the move to the cross-staff and the Davis quadrant