On a clear night far from artificial lights, the night sky in the wilderness is a breathtaking spectacle of countless stars. While this is one of the great joys of trekking, it can also be overwhelming. How does one identify the specific stars that indicate direction amidst this vast, moving canopy?
Although astronavigation is a complex science, fundamental knowledge can help you determine cardinal directions at night. The specific stars you use depend on your hemisphere.
In the Northern Hemisphere
Here, the primary celestial marker is the North Star, Polaris. It remains almost stationary in the sky, indicating true north. Once you locate it, you can easily establish the other directions.
Contrary to popular belief, Polaris is not the brightest star. However, it is relatively easy to find using three key constellations: Ursa Major (the Big Dipper), Ursa Minor (the Little Dipper), and Cassiopeia.
1. Using Ursa Major (the Big Dipper): Identify the two outer stars of the Big Dipper's "bowl" (Dubhe and Merak). Draw an imaginary line through them and extend it outward approximately four to five times the distance between these two pointer stars. This line will lead you to Polaris, which marks the tip of the handle of Ursa Minor (the Little Dipper).
2. Using Cassiopeia: This constellation forms a distinctive "W" or "M" shape. The central star of its main pattern also points roughly toward Polaris, which lies approximately midway between Cassiopeia and the Big Dipper.
Note: Due to the gradual shift of Earth's axis (axial precession), Polaris has not always been and will not always be the North Star. In about a thousand years, the star Gamma Cephei will become the closest bright star to the north celestial pole, but this is not a concern for current navigation.
In the Southern Hemisphere
Polaris is not visible here. Instead, navigators use the constellation Crux, the Southern Cross, to locate south.
Visualize the long axis of the cross (the line through the two stars that form the pole). Extend this imaginary line downward from the foot of the cross for a distance about five times the length of the constellation itself. From this endpoint, drop a perpendicular line to the horizon; this will point to south.
Under Cloudy Skies
Celestial navigation requires a clear view of the stars. However, if you can see a single bright star through breaks in the clouds, you can deduce its general direction by observing its apparent movement.
A simple method:
1. Place two stakes in the ground about 60 cm apart, aligning them precisely with the visible star.
2. Wait and observe for several minutes. The fixed stakes will serve as a reference, and the star will appear to drift.
Interpreting the Drift:
In the Northern Hemisphere:
• Drift to the left indicates the star is in the north.
• Drift to the right indicates the south.
• Drift upward indicates the east.
• Drift downward indicates the west.
In the Southern Hemisphere, the logic is reversed:
• Drift to the left indicates south.
• Drift to the right indicates north.
• Drift upward indicates west.
• Drift downward indicates east.
If the star remains perfectly aligned with your stakes, you have likely found Polaris, as it shows negligible apparent movement.
Next guide: How to Navigate by the Sun on a Hike Previous guide: A Hiking Navigator: An Indispensable Assistant You can view the full list here: Survival Guides for the Mountains
