ISS Pass or Starlink Train: How to Tell the Difference
Learn how to distinguish the ISS, a Starlink train and a single satellite, then predict their next visible pass.
You may sometimes notice a bright light silently crossing the sky. On another night, you might see a line of lights moving in the same direction. The first could be the International Space Station, while the second may be a recently deployed group of Starlink satellites.
What does the ISS look like?
The International Space Station appears as a very bright white point moving steadily without blinking. During a favourable pass, it can become one of the brightest objects in the night sky.
It remains visible for a few minutes. It may then fade or disappear when it enters Earth’s shadow.
What does a Starlink train look like?
After some launches, several Starlink satellites remain close together for a limited time. From the ground, they look like a line of evenly spaced lights travelling in the same direction.
This formation is temporary. The satellites gradually separate as they move towards their operational orbits, making the train less compact and harder to recognize.
What are the main differences?
The ISS looks like a single, often very bright point. A Starlink train contains several aligned lights. A typical satellite also appears as one point, but it is generally dimmer than the ISS.
These objects move steadily and normally do not blink. Flashing lights, red and green colours or audible noise are more likely to indicate an aircraft.
When can you see the ISS?
The ISS is easiest to see when the observer’s sky is dark but the station is still illuminated by sunlight. Times close to sunset and sunrise are therefore often favourable.
Visibility also depends on the elevation of the pass, cloud cover, haze, light pollution and nearby obstacles.
How can you find the pass time?
Pass times change with the observer’s location. A time shared online may not apply to your city.
AstroAlert uses your position and recent orbital data to calculate what will actually pass above you. The app tracks more than 1,000 satellites and highlights high-elevation events.
Never miss the next pass
Go outside two or three minutes before the predicted time and begin with the naked eye. If you want to take a picture, keep your phone stable and turn off the flash.
