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Galileo Portrait by Leoni
Galileo Galilei (1564-1642) was one of the greatest mathematicians and astronomers of all time. Born in Pisa on February 15, 1564, his work radically altered the scientific landscape of his time, setting the stage for much of modern science. By improving the telescope, and by using it to observe the heavens, Galileo amassed evidence for the Copernican idea that the earth revolves around the sun, and that the earth is therefore not the center of the universe. His bold advocacy of the Copernican theory was a challenge to the accepted thought of the time, and ultimately Galileo was tried as a heretic by the Catholic Church. He was forced to recant his views, and he spent the last eight years of his life under house arrest.

Safely Viewing Sunspots
How did the early astronomers manage to look at the sun? One of the methods they figured out was projection. By using a telescope to project a smaller, dimmer image of the sun, they were able to study the sun at their leisure, with no risk to their eyes.

You can use this method to see sunspots for yourself. Please be aware that viewing the sun directly (either with the naked eye or with a telescope) is extremely dangerous.

The safest practical way to see the sun is by lining up a telescope or binoculars on the sun, but instead of looking through the eyepiece, hold a sheet of white paper behind the eyepiece. The solar image is seen projected onto the paper, and you can safely look at it there.

You will need binoculars or a telescope, a camera tripod, a piece of paper or cardboard to create a shadow, a piece of white paper on a clipboard, or poster board, for a screen to project the image on to, and duct tape to hold all the parts in place.


1) First, you should firmly fix the binoculars to a tripod. You can do this with duct tape.

2) Cut out a shield made of cardboard and tape it to the front of the binoculars with the lenses sticking through holes that you cut.

3) Put the lens cap over one of the large binocular lenses or tape over one of the front lenses with duct tape. (You really only need a monocular for this.)

 



4) Use the duct tape to seal any holes that leak light past the cardboard.

5) Point the binoculars toward the sun while holding a piece of white cardboard about a foot behind the eyepiece.

6) It will take a little effort to find the sun. Once you do, you can focus the binoculars to bring the sun to a sharp image.

Be careful not to put your hand or anything flammable near the eyepiece! The concentrated sunlight focused there can cause a nasty burn or set something ablaze! Now you can watch a beautiful, bright, magnified image of the sun. You will have to adjust the tripod to account for the earth's rotation.You may be able to see sunspots. It depends on when in the "sunspot cycle" you decide to do this activity. You may want to jump to
"The Sunspot Cycle" in the Modern Research section to learn more.

One more warning here. You might give your binoculars a cooling break now and then. The eyepiece may become overheated and the lens elements may separate if you leave it on the sun too long.

By making daily observations and recording patterns over time, astronomers like Galileo learned more about sunspots. In the next section, "Modern Research," you will discover how new technologies have added to our understanding of sunspots.

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Observatory  1998 The Exploratorium.