The history of telescopes is the story of two types of telescopes: the refracting telescope and the reflecting telescope. Both were very important in helping us learn about space. In this activity, you will learn more about both types of telescopes.

Refracting Telescopes

In 1609, an Italian mathematics professor named Galileo Galilei peered through a strange new device at the stars. Suddenly, the night sky, so well known and familiar, revealed itself as a barely explored mystery.

The moon is a gray-white orb to the naked eye. Looking through the new instrument, Galileo saw shadows and bright spots that showed the surface had mountains and valleys. The planets, thought to be odd stars that "wandered" the sky, now looked like little globes. Galileo discovered that the planets were accompanied by moving pinpoints of light — their own moons.

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Galileo Galilei

Galileo quickly published his discoveries in a bulletin he titled "Message from the Stars." His claims were met at first with wonder and excitement. He presented his device — eventually named a "telescopio," Greek for "to see at a distance" — to the leaders of the time, including the Catholic Church in Rome.

The first telescope used the same principles that all telescopes would rely upon. The combination of the two lenses gathered more light than the human eye could collect on its own, focused it, and formed an image. Because the image was formed by the bending of light, or refraction, these telescopes came to be known as refracting telescopes, or refractors.

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From: http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/eras/galileo/ 

Refracting telescopes would remain an important tool in studying space until the late 1890s, when they reached their effective peak. Lenses were up to 40 inches in thickness and were becoming too large to work effectively.

Reflecting Telescopes

With refractors growing to over a hundred feet long and increasingly difficult to handle, telescopes were ready for a new design.

They got it — thanks to Sir Isaac Newton, a brilliant scientist at a time when "scientist" wasn't even a word. Newton was known as a "natural philosopher" — he studied the natural world. He used observation, evidence, and calculations as a basis for his conclusions.

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Sir Isaac Newton

 

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Newton's Reflecting Telescope

During the 1680s in England, Newton built a small but powerful telescope. The images produced by this telescope were free from chromatic aberration, the rings of colour that surround bright objects.

He did this by changing the telescope's most basic element: its primary lens. Newton replaced the convex glass lens with a spherical mirror that reflected and focused the light. By changing the primary lens to a mirror, he launched a new class of telescopes: reflectors.

 

Newton's first reflecting telescope, about six inches long, magnified objects almost 40 times — the same magnification as refractors that were three to six feet long. It contained a mirror that was about six inches in diameter.

From: http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/eras/newton/index.php 

That first reflecting telescope has developed into what is currently used to study space. Different types of reflecting telescopes are used all over the world today. The Hubble Telescope is in orbit around Earth.

Multiple mirror telescopes are found all over the planet. These telescopes use many mirrors to get a picture. All of the mirrors in this telescope work together to create one picture.

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In Hawaii, the Keck Telescope has 36 mirrors working together to produce pictures of space. Both of these types of telescopes use light to create a picture of what they are observing.

VLA Telescope

However, not everything in space can be seen. This is where radio telescopes come into play. They can observe information that is not visible, such as radio waves. They can be used as a large group of separate antennas, such as the Very Large Array (VLA) found in New Mexico.

Work on developing even better telescopes continues today as we strive to find out more about space.