Why are some telescopes placed on mountains or in orbit around the earth?
The Earth’s atmosphere has two negative effects on astronomical observations: it blurs the images and it can increase the background, especially in the infrared. Moreover, the atmosphere is transparent only at certain wavelengths so observations in the ultraviolet or in the infrared are hampered. By placing telescopes on a mountain these negative effects are reduced. Operating telescopes outside the Earth’s atmosphere completely removes these effects. There are technologies such as adaptive optics that can reduce or eliminate the atmospheric blurring but the enhanced background – particularly in the infrared where our planet’s temperature makes it “glow”- are much harder to compensate.
