How to: navigate using the stars

Posted on 2 June 2011

Navigating by stars is a relatively simple way to get your bearings at night and it’s the kind of knowledge that can – and has – saved lives.

How it works

Because the Earth rotates, the only (seemingly) motionless points in the night sky are those directly above the North and South Poles (think of a spinning wheel, the hub moves less than the tread). To navigate in the southern hemisphere, you first need to find the southern sky’s only constant point: the South Celestial Pole.

Once you have this point of reference, it will guide you home. Before you lose yourself out there, be aware that the following method works only in the southern hemisphere on cloudless nights.

Find the Southern Cross (the Crux)

Look up to the bright band of the Milky Way and find the really dark patch in the bright span. This is the Coalsack Nebula. Right over it are four bright stars in the shape of a cross – the Southern Cross, also called Crux. To the left of it are another two really bright stars, Alpha and Beta Centauri – commonly called the Pointers. Extend a line connecting Alpha and Beta Centauri toward the top star or head of the Southern Cross. This top star is called Gacrux (a contraction of Gamma and Crux). Opposite it (the foot of the cross) is Acrux (Alpha and Crux) and the arms from left to right are called Becrux and Delcrux. Delcrux is the most pale of the four stars.

Get me outta here

Now that we have the right constellation, we can navigate. There are several ways of identifying due south using the Southern Cross – these are the most popular:

  • Simply extend the long axis (Gacrux – Acrux) four-and-a-half times towards the horizon. Where this ends indicates south.
  • A more accurate way is to draw a perpendicular line from halfway between the Pointers and where this intersects the abovementioned Gacrux – Acrux axisline is south.

Once you know where south is, you can use this as a starting point to travel in any desired direction.

Don’t be fooled by the False Cross

Check that you have the Southern Cross and not the False Cross. The False Cross is diamond-shaped instead of kite-shaped. It doesn’t have a fifth star (Epsilon Crucis) between Delcrux and Acrux, is not as bright and has no pointers.

Check out the PDF for more info on how to navigate using the stars






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