Science Experiment – Count the Stars

By AG Education 4 September 2017
Reading Time: 2 Minutes Print this page
There’s countless stars in the sky…or is there?

Count the stars

There are 200 billion stars in our galaxy, but how many can you see with just your eyes? Some stars are brighter than others, and you need to look carefully to see them all. From very dark places on clear nights you can see almost 2000 stars. The other billions of stars in our Milky Way Galaxy are too faint and far away for us to see them directly. Astronomers use powerful telescopes to view and study the stars.

In this activity you can build a simple viewer to count how many stars are visible in the night sky. Make sure you ask a parent to help!


  • Large piece of stiff cardboard (about 20cm square)
  • Ruler
  • Pencil
  • Scissors
  • Long length of strong string
  • Notebook


  1. Make your viewing frame. Use the ruler and pencil to draw a 1.5cm border along each side of your cardboard. Cut along the border and remove the piece in the middle.
  2. Make a hole in the middle of one border. Cut a length of string about 80xm long and loop it through the whole. Tie the ends of the string into a knot.
  3. Put the string around your neck and hold the frame away from you so that the string is fully stretched. This will make sure that the viewer is always the same distance from your eyes.
  4. Go outside on a clear night and hold the viewer up. Count out how many stars you can see inside the frame. Do this five times, with the viewer pointed towards a different part of the sky. Write the numbers down in your book.
  5. Add up the five numbers that you wrote in the notebook and then divide that by five. That gives you the average number of stars you saw through your viewer.

The window in your frame is about 40 times smaller than the full stretch of the sky. Multiply your average number by 40 to get an estimate of the total number of stars we can see in the night sky. Try using your star viewed in different locations, such as the countryside and city.

Do you want to keep learning? Find more experiments here!