How to use the stars for navigation (in northern and southern hemispheres)
In a wilderness survival situation, you can determine direction using “markers” in the sky, constellations and key stars, that point the way North or South. The astronomical objects to use are dependent upon your location – Northern Hemisphere or Southern Hemisphere.
The Northern Sky (Northern Hemisphere)
In the northern hemisphere, the main constellations that will assist you in navigation are Ursa Major (the Big Dipper) and Cassiopeia (Lazy W). You can use these two constellations to help find Polaris (the North Star). The arrow in the picture below points to Cassiopeia – Ursa Major is located just upward and to the right.
Polaris more or less remains stationary in the night sky. It is the last star in the handle of the Little Dipper (Ursa Minor). To discern between the Big Dipper and the Little Dipper, look for the constellation made of seven dim stars – this is the Little Dipper (the Big Dipper is made of seven brighter stars). To avoid confusion, use the Big Dipper and Cassiopeia together to spot the North Star. The Big Dipper and Cassiopeia are generally opposite each other and rotate counterclockwise around Polaris, with Polaris in the center.
You will use two “pointer stars”, one each from the Big Dipper and Cassiopeia, to form a line that points to the North Star. First, spot the Big Dipper (made of seven bright stars). Next, find the star that makes the outer lip of the dipper, the star located where water would pour out if the dipper were tipped forward. Next find the lower star that makes up the outer lip of the dipper (the bottom, left-hand corner of the dipper). Mentally draw a line from the outer bottom star to the top outer star of the dipper’s bucket. Extend this line about five times the distance between the pointer stars. The North Star will be located along this line and of course, lies in the northern direction of the sky.
Cassiopeia or the Lazy W has five stars that form a shape like a “W.” One side of the “W” appears flattened or “lazy” – that one star is not equally distanced like the other stars in the “W”. Start with a line on the star that makes the bottom, left of the “W” and continue the line right through the middle of the two stars on the “lazy” side. Extend this line about five times the distance between the bottom of the “W” and the top. The North Star is located between Cassiopeia and the Big Dipper).
After locating the North Star, locate the North Pole or true north by drawing an imaginary line directly to the earth.
The Southern Sky (Southern Hemisphere)
Because there is no single star bright enough to be easily recognized near the south celestial pole, you can use a constellation known as the Southern Cross. You can use it as a signpost to the South. The Southern Cross or Crux has five stars. Its four brightest stars form a cross. The two stars that make up the Cross’s long axis are used as a guideline. To determine south, imagine a distance four-and-one-half to five times the distance between these stars and the horizon.
The bright pointer stars to the left of the Southern Cross serve two purposes. First, they provide an additional cue toward south by imagining a line from the stars toward the ground. Second, the pointer stars help accurately identify the true Southern Cross from a similar constellation known as the False Cross. The intersection of the Southern Cross and the two pointer stars is very dark and devoid of stars. This area is called the “coal sac”. Look down to the horizon from this imaginary point to find the southern horizon.