Thousands of people across England will be gazing hopefully up at the stars this weekend – not in an attempt to forecast the next twist of Brexit, but to map out areas of light pollution and genuine darkness.

Clear skies are expected over much of the country for the start of the Star Count, which kicks off on Saturday and will run for three weeks, to 23 February. Participants are being asked to concentrate on the constellation of Orion, which graces the UK’s skies in winter and is easily identifiable.

They will record how many stars they can see within the constellation using only the naked eye. Collating the data they provide will allow the organisers, the Campaign to Protect Rural England and the British Astronomical Association, to map out which areas are worst affected by light pollution.

“A dark sky filled with stars is one of the most magical sights our countryside has to offer,” said Emma Marrington, dark skies campaigner at CPRE. “Increasingly, however, too many people are denied the opportunity to experience this truly natural wonder.”

The last star count was held in 2014, and this year’s will be the sixth since the event started in 2006. By reviving it this year, CPRE hopes to highlight the often overlooked issue of light pollution and encourage ways of preventing the problem.

In 2014, six out of 10 participants could only see 10 stars or fewer within the constellation of Orion, indicating severe light pollution. Only one in 20 people could see more than 30 stars, which is an indication of truly dark skies. Satellite data shows that just over a fifth of England is untouched by light pollution, and more than half of the darkest skies are over national parks and areas of outstanding natural beauty.

Light pollution not only spoils our enjoyment of heavenly bodies, but also disrupts wildlife and disturbs people’s sleeping patterns, with damaging impacts on health, according to studies.

Removing or turning out unnecessary lights is one response to the problem, but local authorities can do much more by using downlighting street lights with reflectors above them, or installing sensors so that street lamps and road lights only turn on when there are people or traffic present. Using lighting more efficiently also reduces energy use and carbon dioxide emissions.

The first week of February is when England experiences its darkest nights, and the count will carry on for three weeks to encompass the half-term holiday for many schoolchildren, making it easier for them to take part.

To see Orion, wait until the sky is as dark as possible, after 7pm, without haze or clouds. Turn towards the south and look for the four corners of Orion’s body and his readily identifiable belt, made up of three bright stars in a straight line. Count the number of stars within the rectangle made by the four corner stars, and include the stars making up the belt.

People all over the UK can take part, but only results from England will be mapped.