How to Read an ISS Pass Prediction
Pass predictions pack a lot into a few numbers. Here's what elevation, duration, and direction actually tell you, and how to use them to find the ISS in the sky.
Elevation
Elevation is the angle above the horizon, measured in degrees. 0° is the horizon itself; 90° is directly overhead. A pass with a maximum elevation of 10° stays low and close to the horizon the whole time — easy to miss behind trees or buildings. A pass with a maximum elevation of 70–80° or higher passes almost straight overhead and is usually the easiest and brightest to spot.
Duration
Duration is how long the station stays above your horizon during that pass, typically anywhere from under a minute to around six minutes. Higher-elevation passes are usually also longer, since the station spends more time above the horizon on a path that goes nearly overhead rather than skimming along the edge of the sky.
Direction
Direction describes where in the sky to look — usually given as a starting compass bearing (where it rises) and an ending bearing (where it sets), sometimes with the point of highest elevation in between. The ISS moves fast: a whole pass takes just a few minutes start to finish, so knowing roughly which direction to face before it appears matters.
What makes a pass "visible" at all
Two things have to be true at the same time:
- The station itself has to be sunlit — not in Earth's shadow.
- Your sky has to already be dark enough to see it, which typically means shortly after sunset or before sunrise.
That's why visible passes cluster around dawn and dusk: during the middle of the night, the ISS is usually in Earth's shadow along with you, and during the day, your sky is too bright to see it even though it's sunlit.
Why cloud cover matters too
None of the above matters if it's overcast. ISS Live Tracker pulls a cloud-cover forecast for each predicted pass, so you can tell at a glance whether it's worth actually going outside — a detail most basic pass-prediction tools skip entirely.
Get pass predictions — elevation, duration, direction, and cloud cover — for your own location.
Get pass predictionsRelated
- What is a TLE? — the orbital data behind every prediction.
- How ISS tracking works — TLEs, SGP4, and pass prediction.
- How to see the ISS — a first-timer’s spotting guide.
- Is the ISS visible tonight? — a live pass finder for your location.
- A free, browser-based alternative to Spot the Station
