To get started you are going to need a few items. Here is a list of the simple items you can put together to create your telescope:
A Pair of Lenses - One Larger Convex and One Smaller Concave (for the lenses, a convex lens is thicker in the center than the edge and the concave is the opposite).
Two Cardboard Tubes - Old wrapping paper tubes are great for this though anything that fits the bill will work.
Building Your Telescope
Now that you have your materials, it's time to put them together. Start by sliding one of the cardboard tubes into the other.
Next, you will need to decide how far apart the lenses need to be. Do this by holding the small lens and looking through it while keeping the large lens in front of you. As soon as you can focus on an object a decent distance away from you, take a measurement of how far apart the lenses are and use this new distance in your construction.
The two tubes put together should be twice the length of the distance between your two lenses. Put the large lens on a single end of the wider tube - gluing it securely into place. Don't get any glue or adhesive on the lens though as it can be distracting when you go to use your home made telescope later on.
Now, place the smaller lens on the opening for the smaller tube to create your eyepiece. Make sure the lenses line up with each other nicely so that you can see directly through them. This means the tubes cannot be bent or broken - they need to be solid and capable of keeping the lenses completely parallel. If not, you may succeed only in giving yourself a bit of a headache.
If you can keep the two lenses the right distance from each other, keep them parallel, and maintain a good line of sight, your new homemade telescope will be the perfect fit for you, your children, or a classroom full of eager young astronomers.