How to See the International Space Station

The International Space Station (ISS) is easy to see from almost anywhere in the US, even from a brightly lit city. NASA calls it the third brightest object in the sky, after the Sun and the Moon. You don’t need a telescope or a dark site. You only need to know when to look, and in which direction.

What a pass looks like

A pass is one trip of the station across your sky. It usually starts low on one horizon, rises to its highest point and sinks toward the opposite horizon, all in a few minutes.

NASA describes it as looking like an airplane or a very bright star moving across the sky. It differs from a plane in two ways:

• It doesn’t blink. Airplanes carry flashing lights. The ISS is a single steady light.
• It doesn’t turn. It follows a smooth, straight path across the sky, without changing direction.

It also moves much faster than a plane. NASA puts its speed at about 17,500 mph (28,000 km/h), compared with about 600 mph for an airliner. Because it orbits about 250 miles up, it still takes a few minutes to cross the sky.

Why only at dawn and dusk

The ISS gives off no light of its own. You see it because it reflects sunlight. A pass is visible only when two things are true at once:

1. Your sky is dark, or at least darkening, so the station stands out.
2. The station is in sunlight, about 250 miles above you.

Those conditions overlap in the hours after sunset and before sunrise. NASA’s Spot the Station FAQ notes that all visible passes happen within a few hours of sunrise or sunset. Your ground has been in shadow for a while, but the station is high enough to still catch the Sun’s rays.

In the middle of the night, the station is usually inside Earth’s shadow, so it passes over you unseen. In daytime it is in sunlight, but the sky is far too bright to pick it out.

Why it sometimes vanishes

Sometimes the ISS fades out partway across the sky, as if it had been switched off. This happens when the station flies into Earth’s shadow, the same way the Sun sets for the astronauts on board. Sky & Telescope notes that the station can turn orange or red as it slips into darkness, much like a setting sun. On morning passes the reverse can happen, and the station seems to appear out of nowhere as it moves into sunlight.

Nothing is wrong. It’s just a sunset or sunrise seen from 250 miles below.

How to read pass predictions

Our ISS page computes the station’s upcoming visible passes for your location, using the latest orbit data. Each pass lists a few details, similar to the ones NASA uses:

• Start time: when the station rises into view, in your local time.
• Duration: how long it stays visible, usually a few minutes.
• Maximum height: how high it climbs, in degrees. The horizon is 0° and straight overhead is 90°.
• Appears and disappears: the compass direction where it comes into view and where it leaves.
• Brightness: an estimate of how bright the pass will be.

To use the height, hold your fist at arm’s length: one fist is about 10 degrees, as NASA’s skywatching FAQ explains. A pass with a maximum height of 40° climbs about four fists above the horizon.

Which passes are worth going out for?

Higher passes are better. A low pass, only 10° or 15° up, stays close to the horizon, where trees and buildings may hide it, and it’s fainter because it’s farther away. NASA’s old Spot the Station website sent alerts only for passes that reached at least 40°. Our tonight score adds half a point for a bright ISS pass and nothing for fainter ones.

Step by step: watching a pass

1. Check the time. Look up the next pass on our ISS page. Times can shift slightly as the station’s orbit changes, so check again on the day.
2. Get outside a few minutes early. Find a spot with an open view in the direction the station will appear and, if you can, the direction where it reaches its highest point.
3. Face where it appears. Look low in that direction at the start time.
4. Watch for a steady, moving light. When you spot it, follow it across the sky. You don’t need to squint or search hard. Once it’s up, it’s usually obvious.
5. Stay with it until it reaches the opposite horizon or fades into Earth’s shadow.

Clouds can hide it, of course. Even partial clouds can block the brief part of the sky where it’s best.

Where you live matters

The ISS orbits at an angle of 51.6 degrees to the equator, so its path covers the Earth between about 51.6 degrees north and south latitude. NASA notes that the station never passes directly overhead north of that line, which takes in much of Alaska. People there can still see it, but lower in the southern sky.

NASA’s app and our ISS page

NASA used to send email and text alerts for listed cities. Spot the Station is now a mobile app. Our ISS page calculates passes for any US location in your browser, with a rule close to the one in NASA’s app: the station must be in sunlight and at least 10° above your horizon while the Sun is at least 6° below it. Our methodology page explains the details.