Skyfix

Star apps ask you to match a chart to the sky and work it out yourself. Skyfix does it the other way round: hold your wrist up towards something bright, and it tells you what you are looking at.

The compass gives the bearing, the accelerometer gives how far up you are pointing, and the app works out which object sits in that direction right now. Sun, moon and the five bright planets come from truncated VSOP87 and ELP-2000; about forty-five bright stars come from a table. All of it is computed on the watch, with refraction near the horizon taken into account.

WHAT IT DOES

• Aim mode: point, and read the name, altitude and compass direction
• Tonight's list, sorted by how high each object stands
• Rise, transit and set for every object
• Moon phase with percentage, moonrise and moonset
• Best viewing moment of the night, scored on altitude, moonlight and cloud
• A compass rose that points you to the object you picked, with a tilt bar
• Five languages and a glance

WHAT IT NEEDS

• A watch with a compass. Everything is worked out on the watch: no phone, no account, no internet
• Calibrate the compass now and then, as you would for navigation