About The Night Sky

A free star chart for any place and time.

The Night Sky shows you what is above your head: the constellations, the brightest stars, the planets and the Moon, for any place on Earth and any date and time. It works in the Northern and Southern Hemisphere, on a phone for use under the real sky, or as a one-page chart you can print.

How to read the chart

The chart is a map of the whole sky at once. The center is straight up and the edge is the horizon, so a star near the middle is high overhead and one near the rim is low. The letters around the edge are compass directions, and the small numbers between them (30°, 60° and so on) are compass bearings in degrees, measured clockwise from north, so you can match them to the compass on your phone. The text under the chart gives the bearing of each planet and the Moon, for example “Saturn (E, 112°, 25° up)”: face 112° on your compass and look 25° above the horizon. Hold the chart over your head and turn it until the direction you are facing is at the bottom. East and west look swapped compared with a street map because you are looking up at the sky, not down at the ground.

Lines join the stars into constellation shapes, and bigger dots are brighter stars. Planets are drawn as diamonds, the Moon as a grey disc, the Sun (when it is above the horizon) as a small disc ringed with rays, and dashed circles mark galaxies, star clusters and nebulae that are worth a look with binoculars.

Frequently asked questions

Is it free, and do I need to install anything?

It is free and there is nothing to install or sign up for. You can add it to your phone's home screen if you want an app-like icon.

Does it work without an internet connection?

Yes. After your first visit the whole app is stored on your device, so it works offline, including in airplane mode and in remote places with no signal. Everything is calculated on your device, and your location is never sent anywhere.

How do I print a star chart?

Choose a place, date and time, then press Print / save as PDF. Printing always uses black ink on white paper and fits a single US Letter or A4 page, even if you are viewing a dark theme on screen.

Can I use it outdoors without ruining my night vision?

Yes. Switch to the red Night theme with the round button in the top corner and turn your screen brightness all the way down. Red light keeps your eyes adapted to the dark, which is why astronomers use red lamps.

What time should I choose?

About one and a half to two hours after sunset is a good time to look, when the sky is properly dark. If you open the page in the daytime it starts with tonight, once the sky is dark at your chosen place. The Sky right now button shows the current sky instead.

Can I share a chart with someone?

Yes. The Share this sky button sends a link to the place you are looking at. By default the link has no date in it, so it opens on the sky of whoever clicks it, tonight or right now. If you change the date or time yourself, the link pins that exact moment, which is handy for a meteor shower or an eclipse.

Does it work in the Southern Hemisphere?

Yes. It includes the southern constellations such as the Southern Cross, Centaurus and Carina, the Magellanic Clouds and Omega Centauri, as well as the northern sky.

How accurate is it?

Positions are accurate to well under a degree, which is finer than the printed chart can show. Planet positions come from NASA JPL's approximate orbital elements and are valid for the years 1800 to 2050. The Moon is accurate to about a third of a degree. The chart does not correct for atmospheric refraction.

Where does the star data come from?

Star positions and names come from the HYG Database, constellation lines from Stellarium's IAU sky culture, and deep-sky objects from OpenNGC, all shared under the Creative Commons CC BY-SA 4.0 license. Planets use the JPL approximate positions of the planets.