Members of the public are being urged to count stars this week as part of efforts to measure how light pollution is affecting views of the UK's night sky.
Details of the number of stars people can see in the constellation of Orion will be used to create a star count map to show the impact of light from towns, cities and roads on dark skies.
The star count is being run by the Campaign to Protect Rural England (CPRE) and the British Astronomical Association's Campaign for Dark Skies (CfDS) as part of efforts to make ministers and councils take action to tackle light pollution.
A recent survey by the two organisations found that more than four-fifths (83 per cent) of people had their view of the night sky affected by light pollution.
The CPRE said the phenomenon not only damaged the character of the countryside but could also disrupt wildlife and affect people's sleeping patterns.
With councils spending 532 million a year on street lighting, which can account for five to 10 per cent of their carbon emissions, efforts to reduce light pollution can save on greenhouse gases and money.
Emma Marrington, rural policy campaigner at CPRE, said: "We want to use this evidence to convince ministers and local councils of the need to take action to tackle it, for example by ensuring that the correct lighting is used only where it is needed and when it is needed."
To take part in the star count, participants must choose a clear night between today and next Sunday, ideally after 7pm, and to count stars in the constellation of Orion that can be seen with the naked eye. For more information visit www.cpre.org.uk/starcount