Light Pollution

demonstrate an understanding of the drawbacks to astronomers of the Earth’s atmosphere and relate these to the need for optical and infra-red observatories to be sited on high mountains or in space
describe some of the major causes of light pollution and demonstrate an understanding of why it is undesirable to astronomers

When it comes to making detailed observations of the sky the Earth's atmosphere just gets in the way. Just as a diver struggles to see through murky water our view of the stars is blurred by the atmosphere, especially in areas where there is a significant amount of chemical and light pollution. Stars near to the horizon are often invisible because of light pollution, an effect known as extinction.

Stars appear bright and distinct against a black background. Light pollution makes the background sky less dark and therefore stars are harder to see.

Sky glow

This is an orange yellow glow above a city of town. It is caused by light which is emitted directly upwards where it then scatters. It makes astronomy anywhere near a city almost impossible, e.g. The Milky Way is just about invisible.

pic   petfishtank.com	pic  Ian Britton - Freefoto.com	pic  NASA
Blimey, where are all the fish?	Not the best place for an observatory	NOT a very good view of the stars
pic  NASA	pic  NASA	pic  NASA
The Gemini South telescope in Chile	The Mount Palomar Observatory in California	The Hubble Space Telescope

Many large telescopes have been built at altitude, e.g. on top of mountains. Why?

The higher up you are the less atmosphere you have to look through.
The air is drier so less infra red radiation is absorbed.
They are also built in remote areas where the effects of human pollution are minimised.

As well as optical astronomy humans also interfere with radio astronomy. radio communications interfere with the very faint radio signals from distant stars and galaxies.

List all the forms of pollution that interfere with astronomy.

Where would be the worst and the best place in the UK to build a large optical telescope?