anthony morris

Celestial Sphere

The celestial sphere

  • An imaginary, hollow dome surrounding the Earth
    • It's essentially the sky we see when we look up
    • Earth's coordinate system has been extended to the sphere
  • It's what you see when you look up at the sky; you are at the center
  • The path the Sun takes on the celestial sphere is called the ecliptic
    • Celestial tilt


  • Vernal Equinox
  • Declination
    • Celestial equivalent of latitude
    • Degrees, arcmin, arcsec
  • Right ascension
    • Celestial equivalent of longitude
    • Hours, mins, sec
  • Altitude
    • Angle from the horizon to a point on the sphere
    • Zenith is 90˚
    • Altitude of Polaris with give you the latitude of where you are on Earth

Local Terms (Relative to Viewer)

  • Zenith
    • Point directly above your head
  • Horizon
    • Where the dome meets the Earth

Space Astronomy