How to build your own telescope

Observing the stars, the moon and the planets has fascinated mankind for thousands of years. In fact, astronomy is said to be the oldest natural science in existence. However, in ancient times the study of celestial bodies was linked to mythological, religious, and cosmogonic ideas.

All this would change after the revolution of Copernicus in the 16th century, and astronomy would become a true science, with all the methods and protocols that this deserves. Today, humanity has advanced technologies to observe the universe, and the sense of wonder that the night sky produces never ceases to mesmerize us.

If you like to observe the night sky, but feel like you can't see much, building your own telescope can help. You will not need to buy too many materials, and after an afternoon of fun you will be able to observe the stars better and feel part of the large group of scientists who have been doing it for thousands of years.

You will need:

  • Two positive power glass lenses, one high focal length for the objective and one short focal length for the eyepiece (you can ask a specialist optics store for help).
  • 1 roll of kitchen paper (only the cardboard tube)
  • 1 large piece of construction paper
  • Scissors
  • Masking tape


  1. Roll the cardboard lengthwise to form a tube approximately the diameter of the lens with the shortest focal length. This tube will become the eyepiece.
  2. Insert the cardboard tube into the paper towel tube. This last tube will be the target. Let go of the inner tube so it can expand inside the outer tube. If the inner tube doesn't slide in properly, remove it, tighten it a little more, and reinsert it into the outer tube until it fits snugly.
  3. Glue the shortest distance lens edges to the end of the inner tube with the help of masking tape. The curve of the lens must face the inside of the tube.
  4. Glue the second lens to the end of the kitchen paper roll, with the curve of the lens pointing away from the tube.
  5. Look through the eyepiece and point the other end of your telescope at a distant object like the stars, but never at the sun!

How does a telescope work?

There are three basic types of telescope: refractor, reflector, and catadioptric. The telescope you just built is a simplified version of a refracting telescope. Basically, the outer lens (objective lens) focuses the image of the distant object, while the inner lens (eyepiece lens) magnifies it, so you can see it more clearly. The size of the image produced by the telescope will depend on the curvature of the lenses you have used. Enjoy your new creation and gaze at the stars like a true scientist!

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