Stars are the primary celestial bodies used for celestial navigation because they are fixed in their positions relative to each other and can be used to determine the observer's location on Earth.

Altitude is the angle between the horizon and the celestial body being observed.

Azimuth is the angle between the celestial body being observed and the observer's meridian.

Declination is the angle between the celestial body being observed and the celestial equator.

Right Ascension is the angle between the celestial body being observed and the vernal equinox.

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

A sextant is the instrument used to measure the altitude of a celestial body.

A compass is the instrument used to measure the azimuth of a celestial body.

A chronometer is the instrument used to measure the time of day.

Index Error is the term for the difference between the observed altitude of a celestial body and its calculated altitude.

Navigational Error is the term for the difference between the observed azimuth of a celestial body and its calculated azimuth.

Celestial Error is the term for the difference between the observed time of day and the calculated time of day.

Line of Position is the term for the line that connects the observer's position with the celestial body being observed.

Fix is the term for the point where two or more lines of position intersect.

Star Fixing is the term for the process of determining a ship's position using two or more lines of position.