Is that a satellite moving across the sky?

If a dot of light glides steadily across the sky without blinking and crosses most of it in a few minutes, it is almost certainly a satellite. Planes blink or show coloured lights, and meteors last a second or less. The brightest satellite you will usually see is the International Space Station, which can outshine every star.

I build Sky Map, the app mentioned below, so weigh my suggestions with that in mind.

How to tell what you are seeing

• Satellite: a steady white point moving in a straight line at an even speed. No blinking. It may slowly brighten or fade.
• Plane: blinking white or red and green lights, often a sound if it is low, and usually a slower crawl.
• Meteor: a quick streak, gone in a second.
• Star or planet: does not move against the other stars over a few minutes.

A line of dots following each other, all along the same path, is usually a group of Starlink satellites seen shortly after a launch, before they spread out.

Why you see them near dusk and dawn

Satellites reflect sunlight. For you to see one, your sky has to be dark while the satellite is still lit by the Sun. That combination happens in the first hours after sunset and the last hours before sunrise. It also explains the odd moment when a satellite fades out halfway across the sky: it has entered Earth’s shadow.

How to see the ISS

1. Look up the passes for your location. NASA runs a free service called Spot the Station that lists visible passes and can send alerts.
2. Note the start direction and time. A visible pass usually lasts a few minutes.
3. Go out a couple of minutes early, face the start direction and look for a bright, steady point rising.
4. No telescope needed. Binoculars add little, because the station moves too fast to hold.

Where an app helps

Sky Map shows stars, planets, constellations and satellites over the camera view when you point your iPhone at the sky, so you can check whether that moving point is a satellite and see what is around it. It gives altitude and azimuth for objects, and Tonight’s Sky Conditions shows cloud cover, humidity and the best time to look. The core sky map works without internet. Sky Map is free to download, the AR view is free, and some features are paid.

Read next: what you can see without a telescope and what is that bright star.