Astronomy & Space

Celestial Coordinate Converter

Equatorial coordinates (RA/Dec) are fixed to the celestial sphere and don't change with time. Horizontal coordinates (Alt/Az) tell you where an object appears from a specific place at a specific moment. This tool converts between them.

Equatorial → Horizontal

Enter RA in decimal hours (0–24) and Dec in decimal degrees (−90 to +90)

Right Ascension (hours)

Declination (degrees)

Observer Latitude (°N)

Observer Longitude (°E)

Horizontal Coordinates

Altitude—

Azimuth—

Cardinal Direction—

Hour Angle—

Visibility—

Sidereal Time (LST)—

Coordinate Reference

Right Ascension (RA): Like celestial longitude, measured in hours east of the vernal equinox (0h to 24h).
Declination (Dec): Like celestial latitude, +90° = north pole, −90° = south pole.
Altitude: Degrees above horizon (0° = horizon, 90° = zenith). Negative = below horizon.
Azimuth: Compass bearing in degrees (0/360° = North, 90° = East, 180° = South, 270° = West).