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Star Count: measuring light pollution

a dark sky at night with hundreds of stars visible in the milky way overhead

When did you last see the Milky Way, that pale band which appears to arch across the night sky, formed from many billions of stars which make up our own galaxy? Our view of the stars is a source of infinite amazement for scientists and casual observers alike.

What is Star Count?

Every year since 2011 CPRE, the countryside charity, has asked people all across the country to become citizen scientists and join in with its Star Count. Taking place in late February and early March, people are asked to choose a clear night and look up at the constellation of Orion, then let CPRE know how many stars they can spot. The results reveal the impact of light pollution in their area.

Results from 2022 show that people were able to enjoy some of the best views of the night sky since Star Count began in 2011. Severe light pollution across the country as a whole was found to be lower than its peak in 2020, for the second year running.

Children can get involved

Stargazing is a great activity for children, which you can do from your doorstep or garden or even through a window. There are lesson plans available for Key Stages 1 and 2 children on the national CPRE website, developed by CPRE with the Royal Astronomical Society.

Don’t forget to look at the moon as well: you can notice its different phases and, with the help of binoculars, pick out its surface features.

During late winter and early spring, without any special equipment, these are two constellations you can easily find on a clear night:

  • The Plough or Great Bear looks like a giant saucepan. You can use it to find north. Draw an imaginary line through the side of the saucepan away from the handle: follow its line upwards until you see a very bright star. That’s the Pole Starand if you stand to face it you are facing north.
  • Orion (the hunter) with his central belt of three stars, is a very distinctive feature in the night sky, especially from January to March. The constellation includes two of the brightest stars in the sky, Rigel and Betelgeuse. These, the belt stars and two others form an hourglass shape.

The impact of light pollution

Sadly there are places in the country where ‘pollution’ by night-time light from many sources spilling into the sky obscures the best view of the stars. Light pollution at night also disrupts wildlife’s natural patterns and can impact on human health too. A really dark sky helps to distinguish rural areas from urban. With light pollution steadily encroaching further into the countryside, CPRE is a leading voice among organisations trying to stop, and even reverse, this trend.

What can you do to help reduce light pollution? You could campaign for dark skies in your locality. You could for example lobby your town or parish council if a local light source is a problem. You could ask the council to ensure that new developments have well-designed lighting schemes or are refused permission if they would cause light pollution in existing dark places. Better design of street lighting can also reduce light pollution.

Have a think about your own house too, as domestic security lighting and garden lighting is a major source of light pollution, especially when left on all night. You can make sure that your exterior house lights only come on when needed and point downwards, just illuminating the area which needs to be lit.

Improved Star Count results across England

In 2020 CPRE’s Star Count results showed that 61% of all participants were living in areas with severe light pollution, defined as being able to see 10 stars or fewer in the constellation of Orion. On the plus side there was a small increase from the previous year in the number of people living in areas with truly dark skies, defined as being able to see more than 30 of Orion’s stars.

In 2021 a record 7,800 people took part in Star Count across the UK, during the period of lockdown. The good news was that the percentage of people nationally able to see 10 stars or fewer in the constellation of Orion fell from 61% in 2020 to 51% in 2021. This meant that light pollution appeared to have diminished. Those able to see more than 30 stars in Orion increased from 3% in 2020 to 5% in 2021: these people were fortunate in being able to enjoy truly dark skies.

Results from 2022 show that some people are able to enjoy the best views of the night sky since Star Count began in 2011. In 2022 for the country as a whole, severe light pollution fell again, to 49% of participants. It’s thought that continued working from home, as well as concerns about energy bills, are driving this trend, resulting in a clearer view of the night sky for more people.

Worrying lack of dark skies in Hertfordshire

In Hertfordshire, 53% of people submitting results saw 10 or fewer stars in Orion in 2021, and were living in areas with severe light pollution. This was perhaps not surprising in one of the most densely populated counties in the UK.

In 2022 there were fewer results submitted from Hertfordshire than in 2021, but of those who participated, 61% were experiencing severe light pollution. And this year no results were received from people who enjoyed truly dark skies. This is concerning and shows that more action is needed to reduce light pollution.

CPRE continues to call on councils and government to take action on light pollution so that more people can enjoy the remarkable tranquillity of a dark starry sky, a distinctive feature of the countryside.

Updated May 2022

a dark sky at night with hundreds of stars visible in the milky way overhead