Navigation: Astronomical Southern Hemisphere South

I was reading a gear list someone posted today and I thought it looked quite good, it even included a map and compass.

Then I realized while I have a compass, I don’t consider it essential.

I consider the map (especially if it is topographical ) essential but not the compass.
I can find my direction at night using the stars and during the day with the sun.

South at night with the stars:

For everyone in the northern hemisphere this is possibly redundant but explains an important point.

In the northern hemisphere finding the north pole star Polaris is quite simple, find the little dipper and follow the handle to Polaris that is always grid north.

This works because the pole star is quite bright and the little dipper is quite distinctive.

In the southern hemisphere not only is Polaris not visible, neither is the little dipper.

We don’t have a pole star but we have a bright distinctive crucifix pattern (Crux) called the southern cross which also has a pair of very bright star close to it Alpha and beta Centuri called ‘the pointers’.

Alpha Centuri is the brightest star in the southern hemisphere is its quite distinctive and is almost always visible.

A line imagined between the pointers if extended will intersect with the top star of the cross.

The long arm of the cross always point to the pole star , may be in any orientation in the sky as it rotates around the pole.

Once the cross is found you simple measure the major axis the longest line in the cross and extend this line out in the direction of the major axis 3.1 times and it will be intersecting with the pole star.

The from that point a line that is perpendicular to the horizon will be south.

The pole star may be visible or not depending on how good star viewing is on the night.

The point is this method help you find something you can’t see ( a non existent southern pole star) to find another thing you cant see ( grid south ) in the dark when you can’t see much anyway.

Quality knowledge allows you to do near impossible things.

One again proof of the idiom One picture, One thousand words.

How to find south using the stars in the southern hemisphere.

There is some debate as to whether  you should use 3 axes or 4 or 4.5, the reality is you will most likely be measuring with fingers spans and the width of your arm so its not that precise.  regardless if you are traveling at night you should be more worried about whats on the ground rather than the exact direction or south to the nearest degree.  If you used a compass you would have to convert magnetic south north to grid north and  you would be hoping for no nearby magnetic anomalies.

Update: having further examined this issue the correct number of axes to use is 3.53, but being that you will most likely be measuring with fingers between 3 and 4 is good enough. I will try to get an estimate of how large the cross axis will appear compared to an out stretched finger. From memory it’s about the width of two fingers.

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