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Narrator: I am going to walk you through how to build a simple cardboard
telescope. The body of the telescope is made from two cardboard tubes
that nest together. Here we have a plastic cap, an optional cardboard
washer of about the same diameter, and a convex lens, also of the same diameter.
For the other end of the telescope, we have a piece of foam with a hole in it,
a cardboard spacer sized to fit inside the piece of foam, and another smaller
convex lens. First we will construct the objective
end of the telescope, which points at the thing you want to look at.
Start by placing the plastic cap on a table with the small lip
on the bottom. If you have a cardboard washer, put it inside the cap.
The lens is curved on one side and flat on the other. You
can determine which is which by rocking it gently on a soft surface, trying to touch only
the edges if possible. You will want to put it inside the cap with the
curved side down. You should then fit the cap onto the end of the larger tube.
Now we want to construct the eyepiece end of the telescope, which is the end you
will look through. Start by placing the piece of foam
down on a the table. Put the cardboard spacer into the hole in the foam and
push it all the way down, until it's flush with the bottom of the hole.
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The small lens may also be curved on one side and flat on the other, but it's much
easier to tell in this case.
Push the lens down into the hole on top of the spacer,
this time with the flat side down--if there is one. Now put the small end of the telescope
down over the foam piece so it's all flush on one side.
Since you will probably be using your telescope indoors, one of the best things
to use to experiment with focus is a clear light bulb.
To do this, you should replace the eyepiece end of the telescope with
a piece of white tissue paper, held in place with a rubber band.
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Point your telescope at a clear light bulb and look at--not through-- the tissue paper.
By sliding the smaller tube in and out of the larger tube, you can bring an
image of the light bulb's filament into focus on the tissue paper.
Because of the simple nature of these telescopes, all of your images will appear to be
inverted.
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