Activity 2 - Finding the South Celestial Pole using the Southern Cross

Aboriginal and Torres Strait Islander People used a variety of techniques to find cardinal points. In this activity, students will learn how to find the South Celestial Pole using the Southern Cross, as Aboriginal people did in the past. It will require teachers to familiarise themselves with the Stellarium astronomy software program beforehand.

Step by Step guide 

What is Stellarium? 

1. Students will open the Stellarium Desktop program, by hovering your cursor over the right of the screen (or by pressing ‘F6’) to select the ‘Location window’ then setting the location to your town or city, and the time to after sunset when it’s dark. 

2. Ask students to find the Southern Cross constellation. Adding the ‘Sky Viewing options’ (or by pressing ‘F4’) and the ‘Modern’ and then clicking ‘Show labels’ and ‘Show constellations lines’ will make this easier. If this doesn’t help, tell students there is a search function if they have difficulty – the Search window (or by pressing ‘F3’) and the search term ‘Crux’ will take students directly there.  

3. Open the “Sky and Viewing Options Window” [or by pressing ‘F4’] and click “Markings”, the fourth option from the tabs across the top. Tick off “Celestial Poles (of date)”, the second option down, on the third, right-hand column. This will show the South Celestial Pole (SCP). 

4. Students can measure the angular distance from Acrux (the brightest star of the Southern Cross) to the SCP by clicking the “angle” button (this will need to be enabled by going to the ‘Configuration window’ (or by pressing ‘F2’), and selecting ‘Plugins’ (the 7^th option along the top tabs), and then ‘Angle Measure’, the second option.  

5. They then click on the star Acrux and drag the mouse over to the SCP. 

6. What is the distance? What combination of hands/fingers would you need to use to measure that distance? Is there anything in the classroom that measures that angle?  

Teachers Note: The distance between Acrux and the South Celestial Pole is ~27°. Students should note that the two stars do not perfectly line up to the SCP. It is an approximation. Have them figure out the best way to accomplish the most accurate measurement. 

1. Once a student finds the SCP, they can see that they simply need to move straight down to the ground to find Due South. 

This further develops students’ ability to estimate, measure, and compare angles using degrees, using the software-app as a protractor (ACMMG112). Students can increase the time to show that all the stars rotate around the CSP.