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Astronomy through the Atmosphere

A dust storm over the Canary Islands

Although the atmosphere of the Earth is very important for life, it does cause many problems for astronomers; problems that are so important that whenever someone wants to build a new, professional telescope, they always put it somewhere where the problems are as small as possible.

Some of the problems include:

  • Weather - It is almost impossible to do astronomy through thick cloud!
  • Light Pollution - Modern towns and cities have lots of lights on at night. These lights fill the sky with a white or orange glow which makes it much more difficult to see the stars.
  • Blurring - The atmosphere acts a bit like "frosted" glass windows and images of stars and galaxies are blurred and fuzzy. Astronomers call this effect seeing. It is the same thing that makes stars appear to "twinkle".
  • Transmission - Many kinds of light, especially those that we cannot see with our eyes, do not get through the atmosphere at all. The amount of light that gets through is called the transmission of the atmosphere - thus the less atmosphere we look through the more we can see.

Therefore, professional telescopes are usually put on high mountains above most of the clouds, well away from towns and cities, and often on islands where the surrounding sea helps to make the atmosphere more stable, so there is less twinkling.