The Southern Cross as a Stargazing Signpost
You can find a lot of great stargazing signposts in the southern skies — and none more so than the Southern Cross, Crux. The constellations that you can find by using the Southern Cross as a signpost are shown the figure.
Picture Crux as a traditional Christian cross, with the long axis running up and down and the short axis running across this, higher up than the centre line of the long axis.
The objects you can find using The Southern Cross as a signpost are:
Crux to the southern pointers: Draw a line from the star δ Cruxis, through the star β Cruxis. This line points to two very bright stars side by side, α and β Centauri, which are known as the southern pointers.
Crux and the southern pointers to the South Pole: If you want to find north in the northern hemisphere, then you can use the pointer stars of the Big Dipper to find the North Star, Polaris. In the southern hemisphere, things get a bit trickier because no south star marks south for you. Instead, you should use two lines: the first line is drawn from γ Cruxis through α Cruxis and extended in that direction. The second line is drawn bisecting α and β Centauri and continuing perpendicularly away from these two stars. Where the first line meets the second line is due south.
Crux to Centaurus: You’ve already found the two brightest stars of the constellation Centaurus the Centaur, α and β Centauri, which make up the centaur’s front legs. To find the rest of this large constellation, look ‘above’ Crux to find the back legs, and above and to the left of the back legs to find the body and head.
Crux to Vela: If you draw a line from left to right along the short axis of Crux and keep going, you eventually find the large constellation Vela the Sail.
Vela to the False Cross: Two of stars at the bottom of Vela, κ and δ Velorum, make up part of the False Cross, along with two stars from the top of Carina the Keel, ε and ι Carinae. Because the False Cross looks like a slightly bigger version of Crux, it’s often mistaken for its more useful namesake by stargazers trying to find south.
Vela to Carina: The constellation Carina the Keel lies beneath Vela. The two stars of Vela that are part of the False Cross, κ and δ Velorum, point to the very bright star Canopus, α Carinae, in Carina.
Crux to Tucana and the Small Magellanic Cloud: If you follow the long axis of Crux down past the South Pole, you’ll eventually come to the Small Magellanic Cloud in the constellation of Tucana.
The False Cross to Dorado and the Large Magellanic Cloud: Similarly, you can use two stars in the False Cross to find the Large Magellanic Cloud. Draw a line from δ Velorum through ε Carinae and keep going to the Large Magellanic Cloud in the constellation of Dorado.