southern cross finding south

The Southern Cross – Finding South

It’s easy to identify the Southern Cross (aka Constellation Crux) as it’s a compact group of bright stars close together in the form of, well, a cross.  The two pointers (aka Constellation Centaurus) are nearby pointing to the cross (diagram below).

So, imagine the line between the two furthest apart stars (in the cross), extend that line for a distance of four and a half times their separation. That location is the south pole in the sky so if you drop your imagined line directly to the horizon – on the horizon, that is due south.

Alternatively, (and my favourite method), determine the point of intersection of (1) the line drawn along the major axis of the cross, with (2) the line drawn as the perpendicular bisector of the two pointers. Where those two meet is the south pole in the sky, drop that point down onto the horizon for due south.

Southern Cross - finding South
Illustration and caption via ABCScience

As the Cross rotates about the South Celestial Pole its major axis always points towards it so the method to locate the south pole always applies whatever the orientation.

There’s a video on this site if you find that easier: Click here.

It’s far easier to do than say. So just have a go at locating the Cross and the Pointers next time you are out under the stars. It’s good practice to use the pointers as the False Cross (not the Southern Cross) has confused some people into using the wrong constellation.

If you are lost at sea, the Southern Cross or the Polaris (in the Northern Hemisphere) will help you find south or north, you’ll still be lost, but you’ll know where north or south is!

Stay tuned for more tips and tricks for navigating – speaking of tips and tricks, check out Lisa Blair’s Emergency Tactics for ocean sailing – a must for everyone on the water: Click here for details.

Keep following us as we will be announcing some new Navigation and Passage Planning courses soon.


Leave a Reply

%d bloggers like this: