Ce-les-tial Lon-gi-tude
/səˈlɛs.tʃəl ˈlɒn.dʒɪ.tjuːd/
The angular distance of a celestial body measured eastward along the ecliptic, starting from the vernal equinox (0° Aries). It determines a planet's position in the zodiac by sign and degree.
Celestial longitude is the most fundamental measurement used in astrology to locate a planet's position. When an astrologer says that Mars is at "15 degrees of Scorpio," they are referring to its celestial longitude. This measurement divides the 360-degree circle of the ecliptic into the twelve 30-degree signs of the tropical zodiac, starting from the vernal point. It is essential to understand that this coordinate defines a planet's sign placement, which is the foundation for determining its domicile, exaltation, and other essential dignities. It is also the basis for calculating aspects between planets, as aspects are specific angular distances in celestial longitude. While celestial latitude measures a planet's deviation north or south of the ecliptic, celestial longitude tells us precisely where the planet is along that primary path.