Constellations in a Cup

This activity has been designed to support students to develop their understanding of how light travels, and their familiarity with common constellations in our night sky.  

In this activity students will 

• Make a constellation projector using a cup 
• Explore how light travels in straight lines 

Suggested questions to engage students 

• Are some cup constellations brighter than others? Why/ why not? 
• Does light travel in straight lines? 
•  Why do different constellations appear at different times of the year? 
• Can you make your constellations appear brighter? How? 

What to do

Students will need the following items:

• Paper, polystyrene or plastic drinking cup 
• Skewer 
• A strong torch
• Pencils or crayons (optional) 
• Constellation design sheet

To begin, download and print out the constellation design sheet. 

• constellations-in-a-cup.pdf|  27.66 KB .pdf file

Students will need to select one of the constellation designs and glue it face up onto the inside bottom of the cup. If you stick the design to the outside of the cup, the constellations will be back to front.

Next, use the skewer to make small holes where the dots are. Make larger holes in the positions where there are larger dots. 

Finally, students will need a room where you can close the curtains and turn off the lights. Alternatively, find a dark region within the room, and simply hold the cup closer to a wall. 

Put the torch into the cup and turn it on. The constellation should appear as dots of light. For best results, adjust the distance between the cup and the wall. 

(Optional) Students may also decorate their cup with pencils and crayons. 

Extension questions

Ask students to compare two different cup constellations.

• Can you see a difference in the clarity of two different constellations? Why do you think this is? 
• Find a friend who made the same constellation as you. What similarities and differences can you see? What factors are at play here? 

Stellarium view for 1am AEDT. The three bright stars of Orion’s belt (or base of the Saucepan) and the red star Betelgeuse will guide you to the Orionids shower. Image: Stellarium.org

Due to the Earth’s orbit around the Sun, the constellations seen in the night sky change throughout the year. The constellation of Orion can be seen during summer evenings and the constellation of Scorpius is in the sky during winter evenings. 

We can’t see these constellations and other stars during the day because our closest star, the sun is so bright. Ask students to try turning on the light on to see how the constellations look.