Night Sky Map
A live, interactive star chart of the whole sky above your location: stars, constellation figures, the planets and the Moon in their real positions for any date and time. Drag the time slider to watch the sky turn, and click anything to learn what it is and when it rises and sets.
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Hold the chart above your head with the bottom edge toward the direction you face. The center is straight overhead (zenith) and the outer circle is the horizon. East is on the left because you are looking up.
How to use the Night Sky Map
- Set your location: pick a city, type latitude and longitude, or press Use my location.
- Choose the time: the chart starts at the current time. Pick another date and time, or drag the slider to move up to 12 hours either way. Press Play to animate.
- Hold the chart overhead with the direction you face at the bottom. The center is straight up and the circle edge is the horizon.
- Click a star, planet or the Moon to see its name, where to look (altitude and compass direction) and when it rises, culminates and sets.
- Use Find to locate a planet, star or constellation, and Download PNG to save the chart.
How the sky map is calculated
Every object's position is converted into two numbers you can point to: altitude (degrees above the horizon) and azimuth (compass direction, 0° = north, 90° = east). For a star with right ascension α and declination δ seen from latitude φ:
- Local sidereal time: LST = GMST + longitude, where GMST = 280.46061837° + 360.98564736629° × (days since J2000) + small terms. The hour angle is H = LST − α.
- Altitude: sin h = sin φ · sin δ + cos φ · cos δ · cos H, plus about 0.5° of atmospheric refraction near the horizon.
- Azimuth: A = atan2(sin H, cos H · sin φ − tan δ · cos φ) + 180°.
The chart uses a stereographic projection centered on the zenith (radius ∝ tan((90° − h)/2)), the same projection used on planispheres, so constellation shapes are not distorted. Planet positions are computed from Keplerian orbits using NASA JPL's approximate orbital elements, corrected for light travel time and precession. The Moon's position includes its main perturbations and the parallax that can shift it by up to 1° as seen from the ground.
Bright stars to start with
| Star | Constellation | Magnitude | Best evening season (N. Hemisphere) | How to find it |
|---|---|---|---|---|
| Sirius | Canis Major | −1.46 | Winter | Follow Orion's belt down and to the left |
| Canopus | Carina | −0.74 | Winter (southern sky) | Low in the south from the southern US; high from the Southern Hemisphere |
| Arcturus | Boötes | −0.05 | Spring–summer | "Arc to Arcturus" along the Big Dipper's handle |
| Vega | Lyra | 0.03 | Summer | Brightest star of the Summer Triangle, nearly overhead |
| Capella | Auriga | 0.08 | Winter | High in the northeast on winter evenings |
| Rigel / Betelgeuse | Orion | 0.13 / ~0.5 | Winter | Opposite corners of Orion; Betelgeuse is the orange one |
| Altair / Deneb | Aquila / Cygnus | 0.76 / 1.25 | Summer–fall | The other two corners of the Summer Triangle |
| Polaris | Ursa Minor | 1.98 | All year | The two end stars of the Big Dipper's bowl point to it; it marks north |
Tips for stargazing
- Find north first. In the Northern Hemisphere, Polaris sits within 1° of the north celestial pole and its altitude equals your latitude.
- Planets don't twinkle much and are not on any star chart, which makes them easy to spot. They always lie near the ecliptic line (turn it on above). See Planets Visible Tonight for times.
- Dark adaptation takes 20–30 minutes. Use a red light and turn your screen brightness down while comparing the chart with the sky.
- The Moon washes out faint stars. The darkest nights are within a few days of new Moon; check the Moon Phase Calculator.
- Use your fist to measure: held at arm's length, a fist covers about 10° of sky, a finger width about 1°.
Frequently asked questions
How do I read this star chart?
The chart is a map of the whole sky. The center is the zenith (straight overhead) and the outer circle is the horizon. Turn the chart so the direction you are facing is at the bottom, hold it up, and the stars near that edge are the ones low in front of you. East and west appear swapped compared with a ground map because you are looking up, not down.
Does it work without internet?
Yes. The star catalog and all of the planet and Moon calculations are built into the page, so once it has loaded it keeps working offline. Your location is only used inside your browser.
How accurate are the positions?
Star positions come from J2000 catalog coordinates corrected for precession. Planets are computed from NASA JPL's approximate orbital elements (valid 1800–2050), typically within a few arcminutes, and the Moon from a series accurate to a few tenths of a degree. That is far better than you can see with the eye on a chart this size.
Why can't I see as many stars as the chart shows?
The chart includes stars down to about magnitude 4.5–5. From a city, light pollution often limits you to magnitude 2–3, so only the brightest stars and planets are visible. Let your eyes adapt to the dark for 20 minutes and go away from lights to see more.
What do the magnitude numbers mean?
Magnitude measures brightness: smaller numbers are brighter, and each step of 1 is about 2.5 times dimmer. Sirius is −1.5, Vega about 0, the Big Dipper stars about 2, and the faintest stars visible from a dark site about 6. Venus can reach −4.7 and the full Moon about −12.7.
Why do the stars move when I use the time slider?
Earth rotates once every 23 hours 56 minutes relative to the stars, so the whole sky appears to turn around the celestial pole, about 15° per hour. Stars rise in the east and set in the west, and stars near the pole circle it without setting.
Can I use it in the Southern Hemisphere?
Yes. Choose a southern city or enter a negative latitude, and the chart shows the southern sky, including the Southern Cross, Alpha and Beta Centauri, Canopus and the Magellanic Clouds.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.