How to Build a Telescope

A telescope is used for viewing objects in the sky. While these are widely available, many of them are expensive. Here is a simple guide on how to build a telescope.

Required Tools and Materials

Cardboard tubes
Convex lens
Concave lens

Step 1

Make sure you have the right lens sizes. The convex lens has to be 1/10th bigger than the concave lens.

Step 2

Peer through the concave lens. Put the convex lens in front of the concave one. If you look into it, distant objects will become more visible.

Step 3

Measure the lens distance between them then double it. Get a couple of cardboard tubes. They have to be as long as the lens’ distance. The first should be able to fit on the second one.

Step 4

To build a telescope, join the convex lens on one of the tube’s bigger ends. You can use the wires to secure the lens. You can also use hot glue or paper clips.

Step 5

Put the concave lens at one of the smaller tube’s ends. You can also fasten the lens using wires, hot glue or paper clips. This lens will serve as the eyepiece.

Step 6

Bring the telescope out during the evenings. Put one of your eyes in the lens. This will let you see the objects more easily.

Step 7

You can use the telescope in different places. But these are most effective in dim places with minimum light. When using this telescope, you may need to use some support for your neck and head.


Make sure you know the difference between convex and concave lenses. The convex lenses are thicker near the edges. Concave lenses are thin in the middle. An example of a convex lens is the magnifying glass.

If you want the best combination possible, use high powered concave lens and a low powered convex lens. These lenses can be purchased in optical shops and online. Reading glasses can be used as convex lenses. You can get concave lenses in a camera viewfinder.

If you want higher magnification, choose one with lower diopter strength. But remember that longer focal length will make the telescope longer. The field of view will also be lower.


Do not gaze at the sun through these lenses.

If you cannot see anything after you build a telescope, adjust the lens position. You should now be able to see things clearly. If it is blurry, make a pinhole in a paper. Put this in the concave lens.

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