This year the southern hemisphere winter solstice will fall on Sunday 21 June. During the solstice, the Australasian Dark Sky Alliance are calling on would-be stargazers to engage in a citizen science project as night falls.

The project aims to map and measure the level of light pollution across the country, while at the same time attempting to break a Guinness World Record for “Most users to take an online environmental sustainability lesson in 24 hours”.

To take part, people will be asked to step outside and count the number of stars they see in the Southern Cross constellation. Participants can register their interest and contribute to the project on the World Light Record website. Marnie Ogg, the CEO and founder of the Australasian Dark Sky Alliance, says that the project will be particularly good for families.

Ogg says that at present, “we don’t have a baseline measurement” when it comes to light pollution in Australia. While it is possible to track light pollution through satellite imagery, we do not have an understanding of “how much light there is on the ground”.

“If you’re looking through a shield of light pollution, you’re going to see less stars,” she says. “At times we’ve looked at the Southern Cross from the steps of the Opera House and only seen three stars.” She quips “it’s more like the southern triangle … But if you’re deep in the heart of country New South Wales or outback Australia you might even have trouble working out where the Southern Cross is, because there’s so many stars around it.”

She says that while astronomers have known that light pollution has an impact on the visibility of stars for hundreds of years, ecologists are now beginning to understand “how much it impacts our wildlife”. Even plants are impacted by how much light pollution there is on the ground.

In addition to helping with the mapping project, Ogg recommends that people can easily reduce light pollution by only using light when it’s really needed (“do you really need to light the palm tree up at 3am?”), switching to amber-coloured light globes – which place less stress on the environment because they do not mimic daylight the way bright, white light does – and using blockout blinds.

“We have plastics that are going to take hundreds of years to remove from the environment,” says Ogg. “But literally as soon as you turn off that light switch you remove that source of stress in the natural environment.

“The thing that I love most about talking about light pollution is that it’s easily eradicated.”