How to see the ISS tonight — and the exact second it disappears

The International Space Station is the easiest thing in the sky to identify once you know what you're looking for: a single, steady, fast-moving point of light, brighter than any star, crossing from one horizon toward the other in a few minutes flat. No blinking, no color change, no stopping — just a bright dot on a straight line. If you've seen a "shooting star" that didn't shoot and didn't twinkle, you've probably already seen it.

Why it's only visible around dawn and dusk

The ISS orbits roughly every 93 minutes — a real number, not a rule of thumb: the TLE (the orbital parameters ground stations publish for it) puts its mean motion at 15.49 revolutions per day, which works out to 92.9 minutes per orbit. At that rate it crosses the sky more than a dozen times in a 24-hour period. You'd think that means constant sightings. It doesn't, for one reason: you can only see it when you're in the dark and it isn't.

The station is invisible except when sunlight is bouncing off it, and you're invisible to it (so to speak) except when your own sky is dark enough to see a point of light against it. Put those together and there's a narrow band where both are true at once: the hour or so after sunset, and the hour or so before sunrise, when the sun has dropped far enough below your horizon to darken your sky — six degrees or more, past civil dusk, the same threshold observatories use for "dark enough" — while the station, hundreds of kilometers up, is still catching direct sunlight. Go much past that window and either the sky's still too bright, or the station itself has flown into Earth's own shadow and simply isn't lit.

That's also why the middle of the night is a dead zone for ISS-watching regardless of how clear the sky is: it's not that the station isn't up there, it's that it's dark, and there's nothing to reflect.

What makes a pass worth going outside for

Not every pass is worth the walk. The station rises and sets down to about 10 degrees above the horizon — barely clearing rooftops and trees — but a pass that only grazes 10–15 degrees is a dim, brief smudge low in the sky, often lost behind buildings before you find it. The passes worth watching climb well higher: 30 degrees or more of peak elevation is roughly a third of the way from the horizon to straight overhead, and that's the bar a pass has to clear before it's worth a notification rather than a shrug.

Brightness helps you find it once you're looking in the right place. The ISS's reference brightness (standard magnitude, the convention satellite observers use) is about -1.8; overhead on a good pass it reaches roughly -3 — brighter than every star in the sky, no exceptions. You won't need to squint.

The exact second it disappears

Here's the part most guides skip: on some passes, the ISS doesn't set below the horizon at the end — it just goes out, mid-sky, while it's still climbing or high overhead. That's not a trick of the eye. It's the station flying out of sunlight and into Earth's own shadow, the same shadow that gives us night down here. We call this the Fade, and it's worth its own explanation — short version: it's a real dimming window, roughly 22 seconds from first noticeably dimmer to gone, not an instant blackout.

Predicting the exact moment is genuinely hard. The Earth's shadow isn't a sharp-edged line — where exactly you place its boundary depends on modeling choices (which Earth radius to use, whether to account for the atmosphere bending sunlight at the edge) that can each shift the computed instant by several seconds. Stack them up and any honest prediction carries something like ±10 seconds of real-world uncertainty, even before the dimming itself takes another 22. That's why a good prediction calls a window, not a tick of a clock.

The quiet part

This is the entire reason SpacePings exists: not another table of every technically-overhead pass, but a single push before the good ones, with the vanish second called inside it -- and a live countdown to that exact moment in the app. See how the quality gate works — free tier, no account required to check tonight's sky.

Want the short version for tonight specifically? See is there an ISS pass tonight and when can I see the ISS.