How to Make a Kid's Telescope

Figure out the focal length of your lenses by having someone shine a flashlight up and down over the lens until it creates a bright point. Measure the distance between the point of light and the lens. Do this with both lenses, and add the two focal lengths together. Then, divide the number by two, and add 1 inch to it to determine the total length of your telescope. Use the scissors or a serrated knife to cut both of the cardboard tubes to the length determined.

Cut two circles out of Manila paper to the size of the diameter of the tubes. Place the lenses in the center of the Manila paper circles, and draw a line around the lense. Cut just inside of this line to create frames for the lenses. Use glue to frame the lenses, and glue the framed lense with the shorter of the two focal lengths into the eyepiece position of the smaller tube. Glue the lens with the longer focal length into the other end of the larger tube.

Slide the smaller tube into the larger tube; this creates a refracting telescope. Put your eye to the eyepiece, and move the outer tube back and forth until you are able to focus on an object clearly.

Decorate your telescope if you like by using a spray adhesive on the cardboard and adding colorful wrapping paper or specialty paper to the outside. You can also paint the scope, or add touches of paint around the lense frames to make it look authentic.