Live Night Sky Map

The circle is the whole sky above you. The centre is the zenith — straight up — and the rim is the horizon. Something halfway between is 45° up. Anything below your horizon is simply not drawn, which is why the chart looks completely different at 9 pm and at 3 am.

One thing catches everyone out: east is on the left. A road map is a view looking down; a sky chart is a view looking up, so the east–west axis flips. Hold a printout above your head with N pointing north and it lines up with the real thing.

To actually find something, use the table rather than the picture. It gives each object's altitude in degrees and the compass direction to face. Your fist at arm's length spans about 10°, a spread hand about 20°, so "40° up in the southeast" is four fists above the horizon on that bearing.

Planets are usually the brightest things in the sky after the Moon, and they are the ones worth finding first because they are unmistakable once you know what to look for.

• They do not twinkle. Stars are points, so atmospheric turbulence makes them scintillate. Planets show a tiny disc, which averages the turbulence out into a steady glow. This is the quickest test there is.
• They sit near a line. All the planets lie close to the ecliptic — the same track the Sun and Moon follow — so they never appear near the celestial pole.
• Colour is a clue. Mars is genuinely orange-red. Jupiter is creamy white and very bright. Saturn is a duller yellow. Venus is brilliant white and only ever appears near sunrise or sunset.
• Venus and Mercury never stray far from the Sun. If the chart shows them, they will be low and close to twilight — Mercury especially is a difficult catch.

Through the night: everything rotates westward at 15° an hour, the same rate as the Sun. The look-ahead slider does exactly this, so you can check whether something currently too low will have risen by the time you go out.

Through the year: a star rises about four minutes earlier each night. That is the gap between the solar day and the sidereal day, and over six months it accumulates to twelve hours — which is why Orion owns the winter sky and is entirely absent in summer.

With latitude: your latitude sets how high the celestial pole sits. Polaris appears at an altitude equal to your latitude, near enough, and stars within that angle of the pole never set at all. From the southern hemisphere the whole thing inverts and the familiar northern constellations are simply unavailable.

Nothing here is an illustration rotated to look plausible. Each dot is a catalogue position pushed through the chain a planetarium uses: local time to UTC using the correct daylight-saving rules for that date, UTC to Julian day to sidereal time, precession to the equinox of date, then equatorial to horizontal coordinates for your latitude and longitude, and finally a stereographic projection onto the disc.

Star positions are accurate to well under an arcsecond, the Sun to better than 0.02°, the Moon to a few arcminutes, and the planets to arcminutes — up to about 0.3° for Jupiter and Saturn, which is roughly two pixels here. Good enough to point you at the right part of the sky, and not an ephemeris.

Everything runs in your browser. If you use the location button the coordinate is read and used locally; it is never transmitted.

Star, constellation and Milky Way data derived from the d3-celestial datasets by Olaf Frohn (BSD 3-Clause), which draw on the HYG database compiled from the Hipparcos, Yale Bright Star and Gliese catalogues. Algorithms follow Jean Meeus, Astronomical Algorithms, and Paul Schlyter's orbital element compilation.