How to Create a Telescope

Creating your own telescope can be done with household items.

Telescopes are optical instruments that magnify distant objects so you can observe and study them more easily. Telescopes can use very different physical principles to work, and can have different magnification strengths, from very low to very powerful magnification. High-powered amateur telescopes can be quite expensive. However, building your own telescope can be a rewarding experience, informing you about the underlying physics of telescope use. You can build a telescope relatively quickly using easily accessible materials.

Things You'll Need

• 2 convex lenses
• Mailing (telescoping) tubes (one of the tubes should be smaller than the other, and fit snugly inside the larger tube)
• Manila file folder
• Scissors
• Serrated knife
• Glue
• Poster board
• Flashlight
• Measuring tape

Instructions

1. Hold the lens approximately 3 feet above the ground, with either side of the lens facing up, then have someone place the flashlight directly on top of the lens. Have the person gradually raise the flashlight until you see the light on the other side of the lens focus (i.e. becomes a single bright point). Measure the distance between the bright point and the lens. Repeat this process for each lens. Depending on how you choose your lenses, they may have different focal lengths.

2. Add the focal lengths of the two lenses together, and divide that length by two. Add an inch to that distance, then cut both mailing tubes to that length using the serrated knife.

3. Use the scissors to cut two circles from the poster board which have the same diameter as the mailing tubes. Within both of these circles, cut another circle with a diameter that is slightly smaller than the diameter of the lenses. The end result will be two annuli (or rings), with an outer diameter and an inner diameter equal to the diameter of the respective mailing tubes and slightly smaller than the diameter of the lenses, respectively.

4. Place glue on the perimeter of the lenses, then place the lenses atop to the inner circle cut from the poster board in the previous step. Push the lens down and wait for the glue to dry, then repeat for the other lens. You should now have two annuli (or rings) made of poster board with a lens covering the hole in the middle of these objects.

5. Glue the poster board circle with the shorter focal length lens to the end of the smaller mailing tube. This will be the eyepiece. Then glue the poster board circle with the longer focal length lens to the end of the larger mailing tube. This will be the objective lens (or the lens that magnifies the object). If the focal length of the two lenses are equal, the choice of lens for the eyepiece and the objective lens does not matter.

6. Slide the smaller mailing tube into the larger mailing tube and adjust until you can see a clear, magnified image. You now have your own telescope.

Tips & Warnings

• Do not use your telescope to look into the Sun, or any other powerful light sources, as this can result in permanent eye damage.

References

• Universe Today: Build a Telescope