Celestial Coordinates
To calculate charts accurately, astrology relies on astronomy’s coordinate systems. These systems describe where a planet lies on the celestial sphere using angles, reference planes, and fixed points like equinoxes. Below is a simple explanation of the coordinate frameworks used in modern computation.
Ecliptic Coordinates (used in astrology)
The ecliptic system is based on the apparent path of the Sun. It is the foundation for zodiac‑based astrology.
- Ecliptic longitude (λ): the position along the zodiac (0° Aries → 360°).
- Ecliptic latitude (β): distance above/below the ecliptic plane.
- Reason it’s used: zodiac signs correspond to longitude segments along the ecliptic.
Equatorial Coordinates (used in astronomy)
Equatorial coordinates map the sky like Earth’s latitude/longitude system projected outward.
- Right Ascension (RA): measured in hours (0h–24h), similar to longitude.
- Declination (Dec): measured in degrees north/south of the celestial equator.
- Used for: telescope pointing, star catalogues, and precise astronomical modeling.
Why coordinate systems matter in astrology
- All planet positions originate from equatorial calculations.
- Ephemerides convert equatorial → ecliptic → zodiac for chart usage.
- Sidereal and True Sidereal systems shift the reference point to fixed stars.