This undated image provided by the Smithsonian Institution showing streetlights on Earth at night, is part of an exhibit at the National Air and Space Museum in Washington entitled: Earth from Space. A dark blue layer was added to the image to show where land masses are located. European cities are especially bright, and in Egypt, lights glitter along the Nile. (AP Photo/Smithsonian)

This undated image provided by the Smithsonian Institution showing streetlights on Earth at night, is part of an exhibit at the National Air and Space Museum in Washington entitled: Earth from Space. A dark blue layer was added to the image to show where land masses are located. European cities are especially bright, and in Egypt, lights glitter along the Nile. (AP Photo/Smithsonian)

PHOTOGRAPHS of the earth taken from space at night show the extent of light from human habitation.

So much of the night sky is lit up from below that about half of the world's population cannot see the stars.

In the United Kingdom, the 2013 Star Count revealed that only 5% of the population could see more than 31 stars on a good night.

While Clarence Valley urban areas do not have as much light pollution as cities, our view of the night sky is still limited by light pollution. Travelling through the darkened countryside towards a town or city, you will notice a halo of light above the settlement from many kilometres away.

This restricts what can be seen of the heavens from the lit area.

What a contrast there is if you visit sparsely populated areas of Australia away from settlement! On a clear night there the stars are dazzling in their numbers and intensity.

Observation of the stars, once the preserve of professional astronomers, now attracts many non-professionals and astrotourism is growing.

Around the globe there are areas which have been given "Dark Sky" status - places where it is possible to see the heavens clearly and these are attracting increasing numbers of tourists.

One of these is the UK's Northumberland Dark Sky Park, about 1500sq km in northern England. Another is the 4300sq km Aoraki Mackenzie Dark Sky Reserve on New Zealand's South Island. In the United States, even though light pollution is a major issue around the large population centres, there are many designated Dark Sky areas.

These include Death Valley National Park, Canyonlands National Park, and Natural Bridges National Monument.

Dark Sky status is conferred by the International Dark Skies Association (IDA) which is based in Tuscon, Arizona (http://darksky.org/). Areas applying for the status have to have taken major steps to avoid light pollution and to have proved that their nights are sufficiently dark.

While Australia does not have any areas with Dark Sky status, it has places - some in our region - which could qualify and potentially boost tourism.

Leonie Blain, Clarence Valley Conservation Coalition