Measuring Light Pollution

Jesus Acosta, the impact of light pollution as seen during a power outage.

Due to light pollution, the night sky over many of our cities is hundreds of times brighter than a natural, starlit sky. This skyglow hides the stars from our sight and prevents us and all life on Earth from experiencing a natural night, even in areas hundreds of miles away from towns and cities.

How can you help?

Lincoln cathedral at night
Lincoln Cathedral. Image: Mark McNeill

Become a Citizen Scientist

The CPRE does an annual star count which you can do from your back garden or yard. Anyone can take part in it, and you don’t need specialist training or equipment. Find out more here.

Participating in the Globe at Night citizen-science campaign is a great way to help our understanding of skyglow and its impact. No special tools are required and observations can easily be reported by smartphone, tablet or computer.

It’s also possible to use your smartphone to make night sky brightness measurements. The Dark Sky Meter app makes use of the iPhone camera to record the brightness of the night sky, while the Loss of the Night app walks the user through the sky as measurements are made with a different sensitive tool – the human eye. It’s available for both Android devices and iPhones. And now, thanks to the MySkyatNight project, you can also do your own analysis of all this available data.

Jodrell Bank under a starry sky but with some light pollution showing in the background
Jodrell Bank under a starry but light polluted sky. Image: Mark McNeill

Another way you can help is by participating in the Cities at Night project, which relies on citizen scientists to map and identify photos of cities taken from the International Space Station. This valuable information helps researchers better assess light pollution across of the globe.

In addition to the smartphone apps and the Globe at Night project, more rigorous, long-term monitoring is also being conducted. The section below describes standards for collecting and reporting skyglow measurements.

How Can You Help With Skyglow Observations?

The introduction of the Sky Quality Meter and the International Year of Astronomy Lightmeter have led to a large number of permanent online skyglow monitoring stations. At the same time, a number of individuals and groups have developed their own non-commercial devices for measuring skyglow.

If there is a dark sky park or reserve near you, they are always on the lookout for volunteers to help them with their dark sky measurements.

a before and after picture showing how bad lighting can be improved using IDA guidelines
a before and after picture showing how bad lighting can be improved using DarkSky guidelines. Image: DarkSky