The supergalactic coordinate system is a reference frame for the supercluster of galaxies that contains the Milky Way galaxy, referenced to a local relatively flat collection of galaxy clusters used to define the supergalactic plane.
The supergalactic plane is more or less perpendicular to the plane of the Milky Way; the angle is 84.5°. As viewed from Earth, the plane traces a great circle across the sky through the following constellations:
- Cassiopeia (in the Milky Way galactic plane)
- Camelopardalis
- Ursa Major
- Coma Berenices (near the Milky Way galactic north pole)
- Virgo
- Centaurus
- Circinus (in the galactic plane)
- Triangulum Australe
- Pavo
- Indus
- Grus
- Sculptor (near the galactic south pole)
- Cetus
- Pisces
- Andromeda
- Perseus