Finding your way around the sky
Directions, altitude and the hand ruler: how to describe where anything is in the night sky.
To find anything in the sky you need two numbers: direction (azimuth) and height (altitude). Every table on this site uses them.
Direction
Azimuth is a compass bearing: 0° north, 90° east, 180° south, 270° west. Use the North Star or your phone compass to orient yourself once, then pick landmarks: a tree to the north, a roof to the south.
Height
Altitude runs from 0° at the horizon to 90° straight overhead (the zenith). You can measure it with your hand at arm’s length:
- little finger: about 1° (twice the width of the full Moon)
- three middle fingers: about 5°
- closed fist: about 10°
- spread hand, thumb to little finger: about 20°
So “Jupiter 25° above the ESE horizon” means: face east-southeast, then stack two and a half fists from the horizon.
The sky turns
Everything rises in the east and sets in the west, about 15° per hour, because Earth rotates. Stars near the celestial pole circle it without setting. Each night the same star rises about four minutes earlier, so the evening sky shifts through the year.