Celestial navigation relies on measuring the altitude of celestial bodies, such as the Sun, Moon, and stars, above the horizon to determine a ship's position.

Altitude is the angle between the horizon and a celestial body, measured in degrees above the horizon.

The Sun is the most commonly used celestial body for celestial navigation due to its consistent position and brightness.

Declination is the angle between the celestial equator and a celestial body, measured in degrees north or south of the celestial equator.

Right ascension is the angle between the vernal equinox and a celestial body, measured in hours, minutes, and seconds.

The sextant is the primary instrument used to measure the altitude of celestial bodies in celestial navigation.

Sight reduction is the process of determining a ship's position using celestial navigation.

Dead reckoning is the process of estimating a ship's position based on its previous position, speed, and direction.

Piloting is the process of navigating a ship using landmarks and visual cues.

The substellar point is the point on the Earth's surface directly below a celestial body.

The zenith is the point on the celestial sphere directly above the observer.

The nadir is the point on the celestial sphere directly opposite the zenith.

The meridian is the great circle on the celestial sphere that passes through the celestial poles and the zenith.

The equator is the great circle on the celestial sphere that is perpendicular to the meridian and passes through the celestial poles.

The ecliptic is the great circle on the celestial sphere that represents the apparent path of the Sun throughout the year.