Scene Free exploration Equatorial (α, δ) Ecliptic (λ, β) Horizontal (A, h) Hour angle (H, δ) Position triangle Sidereal time Solar time Geocentric view Earth rotation Sphere rotation Topocentric view Armillary sphere Zoom Whole sky Earth ▶ ⏮ Speed − + Layers Sphere Horizon Zenith–Nadir N–S / E–W Culmination point Circumpolar circles Meridian Fundamental meridian Equinoctial colure Solstitial colure Equatorial grid Alt-azimuth grid Ecliptic grid Tropics Zodiac Mean Sun Stars Constellations Ecliptic Equator The Earth in the celestial sphere. Observer: —