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Celestial Equatorial (RA/Dec)
Equatorial coordinates
Right Ascension (RA) is like longitude on the celestial sphere (0–360° or hours). Declination (Dec) is like latitude (−90° to +90°).
Celestial sphere (view from outside)
Before you start
Right Ascension and Declination are the celestial equivalent of longitude and latitude — fixed to the stars, not your horizon.
Key idea
RA measures eastward along the celestial equator (in degrees or hours). Dec measures north/south from the celestial equator.
What you see
- Celestial sphere with equator and RA meridian
- Star position set by RA and Dec sliders
Try this
- Set Dec to +90° — the north celestial pole
- Set Dec to 0° and sweep RA — motion along the equator
- Compare with Alt/Az in the related comparison tool
Common mistakes
- Confusing RA hours with degrees (1 h = 15°)
- Expecting RA/Dec to change with time of night (they're fixed on the sphere)
Glossary
- Right Ascension
- Celestial longitude, measured eastward from the vernal equinox.
- Declination
- Celestial latitude, +90° at the north celestial pole.