Constellations are regions of the sky with internationally defined boundaries. The familiar shapes people draw among bright stars are often called asterisms. These patterns are useful signposts, even though their stars may be separated by enormous distances.
Learning to orient yourself
Begin by knowing which way is north, south, east and west. Compare the horizon and sky in front of you to a chart set to your location and time. The visible patterns change with latitude and season.
Three useful patterns
- Orion: recognizable in many regions by three stars forming a short, straight belt.
- The Big Dipper: an asterism within Ursa Major, often used in the Northern Hemisphere to locate Polaris.
- The Summer Triangle: three bright stars—Vega, Deneb and Altair—form a large triangle in northern summer skies.
Why the sky seems to move
Earth's rotation makes stars appear to move across the sky through the night. Earth's orbit around the Sun means different constellations are more prominent at different times of year.
Field tip: Learn one pattern well rather than memorizing dozens. Revisit it at a similar time over several weeks and notice how its position changes.