Science Fair Central

Telescope: Upside Down

Fun Experiment to Try at Home!

Purpose To determine how a telescope works.
Materials
-	two magnifying lenses
Procedure
1.	Close one eye and hold one of the magnifying lenses near but not touching your open eye.
2.	Look at a distant object, such as a tree, through the lens. The object will be blurred. Place the second lens in front of the first lens and slowly move the second lens away from you until the distant object is more clearly visible. Note the orientation of the object. Is it right side up or upside down?
Sum It Up! The upside-down image seen through the two lenses is similar to the images viewed through a refracting telescope. The parts of a telescope can be compared to the lenses in this investigation. The furthermost lens behaves like the objective lens on a telescope in that it gathers light from an object. In a refracting telescope, the objective lens is the larger of the two lenses. The eyepiece, which is the lens you look through, receives the light from the object and magnifies it. Your eye sends an image of the magnified object to your brain. The image seen through a refracting telescope is reversed, as in this investigation. This is not a great problem if you are looking at a star, because it generally looks the same whether it is right side up or upside down. But the moon looks very different, as does the tree you looked at.

Children may have accidentally invented the first telescope.

Some say that children playing in an Amsterdam optical shop invented the first telescope. The shop was owned by the Dutch spectacle-maker, Hans Lippershey. The children happened to look through two lenses at the same time, and they discovered that they could see distant objects as though they were up close. Lippershey is said to have improved on the children's discovery by putting two lenses in a tube, one at each end. He called the invention a "looker" and sold it in his shop. This event occurred some time in the early 1600s. As with many inventions, it is possible that a number of people independently discovered the magnifying effect of using two lenses.

Galileo, an Italian astronomer and physicist (1564-1642), made improvements on the telescope. With his homemade telescopes, he was the first to study and report many astronomical discoveries, such as the fact that Jupiter has moons. The double lenses used by the children, the "looker" made by Lippershey, and the telescopes made by Galileo are all examples of refracting telescopes.

For more information about lenses, read "Janice VanCleave's Microscopes and Magnifying Lenses." (New York: Wiley, 1993)

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