Finding directions from the stars has never been easier. In the modern times, everyone has a phone app.
However, there are some old tricks just in case you run out of battery with or without maps.
Circumpolar stars – always in the sky
Depending on your latitude on Earth, some stars will always be in the sky, unless you are at the Equator. At the Equator you can see all the stars but not in the same time. The stars that are always in the sky are called circumpolar. They go in circles (‘circum’) around the celestial pole (‘polar’).
The Celestial Poles are at the extensions of Earth’s axis
The North Celestial Pole (NCP) and the South Celestial Pole (SCP) are extensions in the sky of Earth’s North and South Pole, along the axis of rotation of Earth. In the Northern Hemisphere there is a star, located one degree from the NCP, called Polaris. If you find that star and drop your sight to the horizon, you will be looking in the direction North. There is a very complicated process to find Polaris, looking at the big and small dipper (if you find them, good luck with that).
However, in the Southern Hemisphere, even though we don’t have a star marking the South Celestial Pole (SCP), finding South by the stars is REALLY easy. (Actually there is a star in there, Sigma Octans, but it’s so dim that you cannot see it without binoculars…, which makes it unusable for stargazing.)
Southern Cross is circumpolar
In the Southern Hemisphere we can find SCP by using the stars that are always in the sky: the circumpolar stars. In particular, we can look at one constellation, the Southern Cross. This is the most famous constellation of New Zealand (and Australia?). It’s the smallest constellation in the sky and the only constellation that fits right inside the Milky Way. If you are lucky enough to see the Milky Way, just follow it through and at any time of the night you will find the Southern Cross.
1. Step One – turn your back to the Sun
If you cannot see the Milky Way and it’s night time, turn your back to that part of the sky where you think you saw the Sun earlier. Sun goes through North in the Southern Hemisphere. If you cannot remember where you saw the Sun earlier and it’s still night, try and locate the Moon. The Moon goes through the Northern part of the sky too. So if you turn your back to that, you are looking roughly South.
2. Look for a circle of stars
If you did figure out which part is South, even roughly, look for a big cross and two other bright stars, which seem like the handle of the cross. They can be anywhere in the sky so don’t aim. At Wellington’s latitude, lowest you will see it will be one time its height above the horizon and highest you will see it is about 60 degrees above the horizon. On the same circle there will be the Diamond Cross, and the False Cross. Then Canopus, and Achernar.
I always thought that Southern Cross looks like the small hand of the clock of the heavens. I call the circumpolar stars here in New Zealand the big clock of the skies because stars turn here, in the Southern Hemisphere, clockwise. And counterclockwise, of course, in the Northern Hemisphere.
So if Southern Cross is at 6 o’clock then the pointers will be to the right. If it’s at 9 o’clock, it will look as if it leans on a side and the pointers will be underneath it. When the Southern Cross is at 12 o’clock the pointers will be to the right and at 3 o’clock above it. You can be sure it’s the Southern Cross if you can fit three fingers (index, middle and ring finger at arm length) in between the two pointers or the short axis of the Southern cross, or four fingers on its long axis.
3. Find the centre of the circle
Once you found the Southern Cross, then picture it as a huge arrowhead. Follow the direction indicated by its longer side and about 2 times the length of your shoulders or 3 times the distance between your thumb and middle finger (at arm length) you will find another star, Achernar.
Southern Cross will ALWAYS point at Achernar (at least during our lifetime)!
Achernar is the 9th brightest in the sky and the only one that bright in that area of the sky.
Now… (drumroll) stretch your arms and place one hand on Achernar and the other hand on the Southern Cross…
You have just found the South Celestial Pole. Let your hands go down and you have found geographical South (and did a bit of stretching at the same time! Not bad…)
Last time I checked there were about 27 ways in which one could find South.
I have learned about this one from a group of scouts (not more than 10 years old) who came at Carter Observatory many years ago. I never had the chance to say thank you enough to them for enlightening, amusing and entertaining me!
So thank you,
Clear skies, wherever you guys are!