GUIDES / PREDICTIONS
Pass tables or an app — which should you use
By Jeroen Wouda · 2 November 2026 · Predictions
Two ways of looking up a pass dominate: a table of times and numbers, or an app that notifies you and points at the sky. They are not rivals. Both are fed by the same orbital element sets and the same propagation model, so neither is inherently more accurate than the other. The difference lies in how you use them, and in the mistakes each one invites.
What a table gives you
A pass table is a list: date, start time, direction of appearance, maximum elevation, direction of disappearance, duration, and often a brightness estimate. Read a week of rows and patterns appear. You can see that Tuesday's pass goes almost overhead while Thursday's barely clears the rooftops, and decide that Tuesday is the one worth standing outside for.
Tables have three practical advantages. They work on paper, so there is nothing to charge and nothing to drop. They show several passes at once, which is the only way to choose between them. And they give you numbers you can act on: an elevation figure tells you whether a tree or a building will be in the way before you put your coat on.
There is a fourth, less obvious one. A table makes the prediction visible as data. You can see how the times shift from day to day, notice that a pass has vanished from the list, and develop a feel for what a good pass looks like. An app that only tells you when to go outside hides all of that.
What an app gives you
An app's real value is the reminder. A notification two minutes before a pass removes the entire planning step, which matters if you are not in the habit of checking. The second value is orientation: a sky view or compass overlay can tell you which way to face when "azimuth 231 degrees" means nothing to you.
Neither of those is a prediction advantage. It is convenience, and convenience is why most people see their first pass.
Where apps mislead
Phone compasses are the weak point. They read the magnetic field, which is offset from true north by an amount that depends on where you are, and they are easily confused by steel in a balcony railing, a magnetic case, a speaker or a car nearby. The resulting error can be large, and the app rarely tells you. If the arrow says the pass will appear over a particular rooftop and nothing happens there, the compass is the first suspect, not the prediction.
Augmented reality overlays have a second problem: they are hard to align against a featureless twilight sky. You end up waving the phone around while the pass is already underway.
The third issue is your eyes. A bright screen destroys dark adaptation in seconds, and recovery takes many minutes. If you use an app, set the brightness to its lowest level before you go outside, and put the phone away as soon as you know which way to look.
Where tables fall short
A table will not remind you. It also assumes you can turn a number into a direction, which takes a little practice: 0 degrees is north, 90 east, 180 south, 270 west, and everything else falls between. And a table cannot tell you that the pass is happening now, which is exactly the moment when a notification earns its place.
A combination that works
Check the table the day before and pick one or two passes worth the trouble: high elevation, a sensible hour, a brightness figure that suggests you will actually see something. Set an alarm for a couple of minutes before the first. Use the phone only to establish the direction, then put it away and let your eyes adjust.
That sequence uses each tool for what it is good at. The table chooses. The phone orients. Your eyes do the part that matters.
One thing neither can fix
Both the table and the app depend on the element set behind them. If the station has fired its engines to raise its orbit, or if the element set is several days old, the pass can shift or disappear, and no interface will warn you. Checking again on the day is not paranoia; it is the correct use of the data.
Where to go next
- Start with the ISS pass tables and see how a week of passes compares.
- How TLE data and SGP4 predictions work explains what is behind both the table and the app.
- Spotting the ISS from a balcony or small garden turns the numbers into a place to stand.
More guides
- How TLE data and SGP4 predictions work — Element sets, propagation and plain geometry — how two lines of text become a time, a direction and a brightness.
- Best time of year to watch the ISS — There is no single best month. The good weeks depend on the angle between the orbit and the Sun, and here is how that cycle works.
- What the ISS actually looks like from the ground — Why the space station is a point of light rather than a shape, and why its brightness changes from one pass to the next.