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Constellation Sky Chart (2D) — Real Star Positions

A real planisphere-style sky chart: actual J2000 right-ascension/declination star coordinates and true visual magnitudes, projected to a zenith-centred, horizon-ringed view with the alt-azimuth formulas real astronomers use. Drag local sidereal time and observer latitude to watch Orion, the Big Dipper, Cassiopeia, Scorpius, Cygnus and the Southern Cross rise, cross the sky and set.

Space & Astronomy2DModerate60 FPS📱 Mobile-adapted⇄ 3D version

This 2D companion swaps the 3D version's randomly scattered, fictitiously-named star field for a genuine planisphere: real J2000 right-ascension/declination coordinates and true apparent magnitudes for the named stars of Orion, the Big Dipper (Ursa Major), Cassiopeia, Scorpius, Cygnus and the Southern Cross, projected with the same alt-azimuth spherical-astronomy formulas real star charts use. Drag local sidereal time to watch the sky's true diurnal rotation carry constellations from horizon to horizon, and drag latitude to see which patterns are circumpolar, seasonal, or never visible from a given hemisphere.

⚙ Under the hood

A real planisphere-style sky chart: actual J2000 right-ascension/declination star coordinates and true visual magnitudes for Orion, the Big Dipper, Cassiopeia, Scorpius, Cygnus and the Southern Cross, projected to a zenith-centred, horizon-ringed view with the same alt-azimuth formulas real astronomers use. Drag local sidereal time and observer latitude to watch constellations rise, cross the sky and set, or disappear below the horizon entirely.

constellationsstar chartright ascensiondeclinationalt-azimuthplanisphere2D

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install