Telescope

A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally, it was an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects – an optical telescope. Today, the word "telescope" refers to many kinds of instruments that can detect different parts of the electromagnetic spectrum, and sometimes even other kinds of signals.

The first practical telescopes were refracting telescopes with glass lenses, invented in the Netherlands in the early 1600s. People used these telescopes for looking at things on Earth and also for studying the stars and planets, a field called astronomy.

Soon after, the reflecting telescope was invented. Instead of lenses, it uses mirrors to gather and focus light. During the 1900s, scientists created many new kinds of telescopes, such as radio telescopes in the 1930s and infrared telescopes in the 1960s, allowing us to see the universe in even more ways.

Etymology

The word telescope was first used in 1611 by a Greek mathematician named Giovanni Demisiani. He used it to describe one of Galileo Galilei’s instruments that he showed at a special dinner at the Accademia dei Lincei. The word comes from ancient Greek words meaning “far-seeing.”

History

Main article: History of the telescope

The first telescope was made in 1608 by a spectacle maker in the Netherlands named Hans Lipperhey. Soon after, Galileo built his own telescope and used it to observe the stars and planets.

Later, scientists found that using mirrors instead of lenses could improve telescopes. In 1668, Isaac Newton built the first practical mirror telescope. In the 1900s, telescopes were developed to see different kinds of light, like radio waves, which opened new windows to the universe.

In space

Main article: Space telescope

Because Earth's air blocks most types of light, scientists can only see a few kinds of light from the ground, like visible light and some radio waves. To see other kinds of light, like X-rays or far-infrared light, telescopes need to be placed in space, above the air. Putting telescopes in space helps avoid problems like clouds, blurry images caused by air movement, and too much light from cities.

There are many important telescopes in space. Some of them include the Hubble Space Telescope, which looks at visible, ultraviolet, and near-infrared light. The Spitzer Space Telescope looks at infrared light, and the Kepler Space Telescope found thousands of planets around other stars. The most recent one is the James Webb Space Telescope, launched on December 25, 2021. It also looks at infrared light. However, space telescopes are harder and more expensive to build and maintain than telescopes on Earth.

By electromagnetic spectrum

The name "telescope" includes many different kinds of instruments. Most telescopes detect electromagnetic radiation, but they collect it in different ways depending on the type of radiation.

Telescopes can be used to observe infrared light, visible light, ultraviolet light, X-rays, and gamma rays. Some telescopes, like the James Clerk Maxwell Telescope, use large dishes to collect radio waves. Others, like the Hubble Space Telescope, use mirrors to gather visible and infrared light. Special mirrors are used to observe ultraviolet light, and X-ray telescopes use unique designs to reflect these very energetic rays. Gamma-ray telescopes often use masks to create images from the patterns they form.

Lists of telescopes

Here are some helpful lists of different kinds of telescopes:

• List of optical telescopes
• List of largest optical reflecting telescopes
• List of largest optical refracting telescopes
• List of largest optical telescopes historically
• List of radio telescopes
• List of solar telescopes
• List of space observatories
• List of telescope parts and construction
• List of telescope types