How do celestial navigation sights and horizons work?

Celestial navigation is the practice of determining a physical position using stars, the Sun, the Moon, or planets without relying on electronic satellite systems. Navigators typically take timed angular measurements, called sights, between a celestial body and the visible horizon using an instrument like a sextant. These measured altitudes and exact times allow them to calculate position lines on charts.

What we know

• Celestial navigation uses timed angular measurements, or sights, typically taken between a celestial body and the visible horizon. [2]
• A sextant is a doubly reflecting navigation instrument used to measure the angle between an astronomical object and the horizon. [4]
• Navigators can estimate latitude by sighting the Sun at noon or Polaris at night using sight reduction. [4]
• Celestial navigation can also be performed without reference to the Earth's horizon by measuring between celestial bodies, such as in lunar distance methods. [2]

Where to go next

• how it workedWhat is a sextant and how do you use it?
• compared withHow does dead reckoning differ from celestial navigation?
• the bigger pictureWhat are the four general categories of navigation?
• whoWho invented the foundational principles of the sextant?
• what followedHow do modern smartphones calculate navigational positions?
• an unexpected connectionHow did Isaac Newton influence modern sextants?Although John Hadley and Thomas Godfrey are credited with implementing the sextant around 1731, the principle was also later found in Isaac Newton's unpublished writings.

Sources

• [1]celestial navigation (Wikidata Q1063512) · CC0 1.0
• [2]Celestial navigation · CC BY-SA 4.0
• [3]Navigational algorithms · CC BY-SA 4.0
• [4]Sextant · CC BY-SA 4.0
• [5]Navigation · CC BY-SA 4.0