Collect two cardboard tubes (like paper towel or mailing tubes—one should fit inside the other with a little wiggle room), two magnifying glasses with different strengths (found at dollar stores or online), tape, scissors, and optionally black paint or paper to reduce glare inside the tubes. You'll also need a ruler for measuring. Most materials cost under $10 total and can be found around the house or at craft stores.

Secure the stronger magnifying glass (eyepiece) to one end of the smaller tube using tape. Make sure it's centered and firmly attached. Then tape the weaker magnifying glass to the end of the larger tube. The lenses should face inward toward each other. You might need to remove the handles from the magnifying glasses first—just tape or glue the lens rims directly to the cardboard.

Slide the smaller tube (with eyepiece) into the larger tube (with objective lens) so you can adjust the distance between the two lenses. This distance determines focus—you'll slide the tubes in and out until distant objects appear clear. Optionally, line the inside of the tubes with black paper to reduce stray light. Decorate the outside if you want, but keep the inside dark for best viewing.

Take your telescope outside or to a window and point it at something far away—a tree, street sign, or distant building (never the sun—it can damage your eyes!). Look through the eyepiece and slowly slide the inner tube in and out until the image becomes clear. It might take some practice to find the right focus distance. The image will appear upside-down, which is normal for simple refractor telescopes.

Use your telescope to observe the world around you. Look at distant landmarks, birds in trees, or the moon at night (the moon is safe and amazing through even a simple telescope!). Talk about how telescopes work—they gather and focus light using lenses. Discuss how real telescopes helped scientists discover planets, stars, and galaxies. Reflect on what you learned about light, lenses, and optics through this hands-on project.