In order to build a simple telescope, you will need a magnifying glass and a pair of weak reading glasses that can be purchased at a drugstore. While the magnifying glass serves as the eyepiece to your telescope, a single lens from the glasses will be the objective lens. This lens draws the light from stars or other types of objects that emit light.
Pop one lens out of the reading glasses to serve as the short lens of the telescope.
Point a flashlight above the short lens. Raise it up and down until the light radiating through the lens sharpens to a point. Measure the distance between the lens and the point. That is the focal length for your short lens. Write the number down.
Pop the glass out of the magnifying glass. This will serve as your long lens.
Point the flashlight above the long lens. Repeat Step 2.
Add the focal lengths of the short and long lenses. Divide the sum in half. Add an inch. The result is the length of each tube.
Use a serrated knife to cut the two tubes to the length determined in Step 5. The tubes should be the same size.
Cut two circles that are the same size from the poster board. The circles must be larger than either lens and fit the ends of the tubes. They will serve as the mounts for your lenses.
Cut a hole in the middle of one circle that is slighter smaller than the short lens. Glue the edges of the lens to the mount. Repeat this step for the long lens.
Glue the mount with the long lens to the end of the narrower tube. This is your eyepiece. Glue the other mount with the short lens to the end of the wider tube.
Insert the narrow tube into the wide tube. Peer through the eyepiece of your refracting telescope. Pinpoint an object in the distance. Slide the narrow tube in and out of the wide tube until the object comes into focus.