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than the other two functions of a telescope. The amount of magnification is determined by the eyepiece.
Changing eyepieces changes the amount of magnification.

Many people incorrectly think that magnifying power is the most important function of a telescope.
However, magnifying a blurry image will simply produce a bigger blurry image; the other two functions that
improve the image quality are more important.

How Do Telescopes Work?

There are two basic types of telescopes. Reflecting telescopes use mirrors as the main light-gathering
element; refracting telescopes use lenses. Because there are engineering limitations on how large a
lens can be made, most large astronomical telescopes are reflecting telescopes.

What about the Rest of the Electromagnetic Spectrum?

Astronomers use telescopes that cover the entire electromagnetic spectrum because celestial objects
emit radiation throughout the entire spectrum. At infrared wavelengths ground-based optical telescopes
with minor modifications and special instrumentations are used as infrared telescopes. Some infrared
wavelengths are absorbed by the atmosphere and require telescopes launched by satellites.

Most ultraviolet, X-ray, and gamma ray wavelengths are absorbed by the atmosphere. At these
wavelengths, astronomers must use satellite-borne telescopes. X-ray and gamma ray telescopes borrow
detection techniques from high-energy elementary particle physics and bear little resemblance to optical
telescopes.

Radio telescopes are basically large concave radio antennas that look similar to the antennas for satellite
TV reception. Radio telescopes can be as large as hundreds of feet in diameter.

Contrary to popular belief, astronomers seldom look through telescopes. Rather, they mount various types
of instruments on the end of telescopes. Digital cameras have largely replaced traditional photography. To
study chemical compositions of celestial objects, astronomers mount a spectroscope on the end of the
telescope. Other types of instruments have more specialized functions, but generally data is recorded
digitally and analyzed by computers.

The Solar System

Our solar system consists of the Sun, a star named Sol, and eight
planets orbiting it. In addition, there are numerous
moons, comets, asteroids, and other smaller bodies in the solar
system.

According to the International Astronomical Union's (IAU) latest
definition (2006), a planet is "a celestial body that (a) is in orbit around
the Sun, (b) has sufficient mass for its self-gravity to overcome rigid
body forces so that it assumes a hydrostatic equilibrium (nearly round)
shape and (c) has cleared the neighborhood around its orbit." The
planets in order out from the Sun are Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus, and Neptune. There are two basic
classifications of planets in the solar system. The inner planets, which
are Mercury, Venus, Earth, and Mars, are all roughly similar in size and composition. Being somewhat like
Earth, the inner planets are classified as the terrestrial planets. Earth's Moon is also classified as a
terrestrial planet, and many astronomers consider the Earth and Moon system as a double planet system.
Terrestrial planets are basically small balls of rock. Jupiter, Saturn, Uranus, and Neptune form the other