Every night at 02:00 local, Skyset downloads fresh orbital elements for about 9,400 objects. That is the only thing it needs the internet for; after the download it can predict passes for 14 days without a connection.

Your spot

The built-in GPS fixes your position to a few metres. From there the set works out, minute by minute, where each object will be in your sky.

What you can actually see

Most passes are invisible: the satellite is in the Earth’s shadow, the sky is too bright, or it never rises high enough. Skyset keeps a pass only if the object is sunlit, your sky is dark and the pass climbs above 20 degrees. That rule removes about 90 per cent of the list.

The chime

Two minutes before a bright pass, the set chimes once and the tube switches to the Sky channel with an arrow and a height: Look up, north-north-east, 42 degrees. Two minutes is long enough to find a window and short enough that you don’t forget.