Finding True South in the Southern Hemisphere
The Southern Cross, or the Constellation of Crux, – as the name implies – is just visible in the Southern Hemisphere. It consists of the Cross itself and the two pointers, which are Alpha-(Rigil Kent) and Beta-Centauri (Hadar) . Finding direction True South with the Southern Cross is easy. First the correct Southern Cross has to be found in the night sky. There are other cross-like constellations of stars resembling the Southern Cross. These however are larger and not having the two distinctive pointers.
If the correct Southern Cross was found, the distance between Gamma- and Alpha-Cruz is extended 4,5 times along this line. And from that point draw a vertical line down to the horizon, which will show True South. The crossing point is called ‘Celestial South’.
As an alternative and more precise method, a line from Gamma- to Alpha-Cruz can be drawn. A second line is drawn perpendicular to the line of Alpha-(Rigil Kent) and Beta-Centauri (Hadar) – the two pointers. Where these two lines are meeting, there is the Celestial South Pole und vertically below that True South.
In practice, this second alternative is better suited for drawing lines on a kitchen table. In the field it is fully sufficient, to extend the long Crux axis 4,5 times for finding True South.
Lessons learned for finding True South with the Southern Cross
- It is important to find the correct Southern Cross in the night sky by practicing and memorizing the Constellation picture, including the two pointers
- Extending the long axis (Gamma-Cruz – Alpha Cruz) 4,5 times will result in finding the Celestial South Pole and vertically down True South.