The ISS is the brightest satellite: a steady light that crosses the sky in a few minutes
The International Space Station orbits about 420 km up, once every 92 minutes, on an orbit tilted 51.6° to the equator, so it passes over nearly every inhabited place on Earth. On a high pass it reaches about magnitude -4 to -5, brighter than any star and close to Venus. It does not blink, makes no sound and moves steadily from west to east.
Passes come in runs. For a week or two the station is visible in the evening, then it moves to the morning sky, and some weeks it is not visible at all. A pass often ends partway across the sky: the station fades out over a few seconds as it enters Earth's shadow.
NASA's Spot the Station service sends a text or email alert only for good passes, those that climb at least 40° above the horizon, about four fist-widths at arm's length. The alert gives the time, how long the station is visible, its highest point, and where it appears and disappears. North of about 51° the station rarely climbs that high, so check the full list of passes instead.
NASA plans to retire the station and steer it into the remote South Pacific at the end of 2030 or early in 2031, using a modified SpaceX Dragon called the US Deorbit Vehicle. A decision in 2027 could extend it.
China's Tiangong station is the second brightest, about as bright as Jupiter
Tiangong, the Heavenly Palace, has been crewed by three taikonauts at a time since it was completed in 2022. It is about a quarter of the ISS's mass and orbits a little lower, about 390 km up, on an orbit tilted 41.5° to the equator. On a good pass it reaches about magnitude -2. It looks just like the ISS: a steady light moving west to east, fading as it enters Earth's shadow. Heavens-Above and N2YO predict its passes.
Some nights both stations pass within minutes of each other. Because Tiangong's orbit is tilted less, it is seen less often from northern Canada and northern Europe than the ISS.
A Starlink train is a fresh launch: the line breaks up within a week or two
SpaceX launches Starlink satellites in batches of 20 or more and releases them close together at about 300 km. For the first few nights they follow one another along the same path, a line of evenly spaced magnitude 2 or 3 dots that is one of the most reported "UFO" sightings. Each satellite then climbs to its working height of about 550 km with its own thruster, the line stretches and breaks up, and the satellites fade to about magnitude 5.5 or fainter.
About 10,000 Starlink satellites were working in late 2026, by far the largest constellation. SpaceX launches every few days, so a fresh train is somewhere in the world most weeks: look one to five nights after a launch, in the first two hours after dusk or before dawn.
China is building two constellations of its own, Guowang and Qianfan, also called Thousand Sails, each planned for more than 10,000 satellites. A few hundred of each were in orbit in late 2026, and their new launches form trains too.
Satellites are visible only while sunlit over a dark sky, so look in the two hours after dusk and before dawn
The higher a satellite, the longer it stays in sunlight after your sunset. A satellite straight overhead stays lit until the Sun is 20° below the horizon for the ISS, roughly 1.5 to 2 hours after sunset at mid-northern latitudes. Low in the sky toward the west after dusk, or toward the east before dawn, satellites stay lit longer.
Near the June solstice the Sun never sinks far below the northern horizon, so at higher latitudes satellites are lit all night. In the table, Sun limit is how far the Sun can be below the horizon with the satellite overhead still lit; All night, June is the latitude north of which the satellite stays lit overhead through the shortest night of the year.
| Satellite | Height km | Sun limit | All night, June |
|---|---|---|---|
| Starlink train, days after launch | 300 | 17° | 49°N |
| Tiangong | 390 | 20° | 47°N |
| ISS | 420 | 20° | 46°N |
| Starlink at its working height | 550 | 23° | 44°N |
In winter the opposite holds: the long nights leave a dark stretch around midnight when no low satellite is visible.
A satellite is a steady light that does not blink; an aircraft blinks
| What it is | Brightness | How it moves | Blinks? |
|---|---|---|---|
| ISS | Brighter than any star, up to about magnitude -5 | Steady white light, west to east, in a few minutes | No |
| Tiangong | Up to about magnitude -2, like Jupiter | Steady light, west to east, in a few minutes | No |
| Starlink train | Magnitude 2 to 3 each, a line of up to dozens | Evenly spaced dots following one path | No |
| Single satellite | Magnitude 3 to 6 | Steady, moving slowly among the stars | Sometimes a slow pulse if it tumbles |
| Satellite flare | A brief brightening, then gone | A moving star that flashes for seconds | One flash |
| Aircraft | Bright | Slower, often with a sound | Yes: red, green and white lights |
| Meteor | Faint to brilliant | A streak that lasts a second or less | No |
The flares of the old Iridium satellites, which could briefly outshine Venus, ended when the first-generation Iridium satellites were retired in 2019. Brief glints still happen when sunlight catches a solar panel, including on the ISS.
Photograph a pass with a camera on a tripod and a long exposure
No telescope is needed. Set a camera on a tripod, focus on a bright star, and use a wide lens, ISO 400 to 800 and an exposure of 10 to 30 seconds. Start the exposure as the satellite appears; for a whole pass, take back-to-back exposures and stack them into one trail. The ISS leaves a bright arc, and a Starlink train leaves parallel lines.
For the ultimate shot, catch the station crossing the face of the Sun or the Moon. A transit lasts about a second and is visible only along a strip a few kilometers wide, so photographers use transit-finder websites to pick a spot and record video. Never look at or photograph the Sun without a proper solar filter.
Satellite trails in deep-sky images are removed by stacking with sigma clipping
Long exposures of galaxies and nebulae now often catch satellite trails, most in the hours after dusk and before dawn. Take many shorter exposures and stack them with a sigma-clipping method, such as kappa-sigma in DeepSkyStacker or winsorized sigma clipping in Siril or PixInsight: a trail appears in only one frame, so the stacking software throws those pixels away. Ten frames or more work well. Imaging the hours around midnight, when low satellites are in Earth's shadow, also cuts the number of trails.
Pass predictions for your location come from tracking sites, updated daily
Satellite orbits change too often to list here. These free tools predict passes for your location:
- Spot the Station: NASA's ISS alerts by email or text, and an app.
- Heavens-Above: the ISS, Tiangong, Starlink and thousands of other satellites, with sky charts of each pass.
- N2YO: live tracking and 10-day predictions for any satellite.
Plan the rest of the night with the astronomy events page and the astronomy calendar. Satellites are bright enough to see from any city; for the faint stars and galaxies, find a dark sky place.