You might think the sky you see at night is dark. In fact, dark skies are getting increasingly rare, with the Milky Way no longer visible to 60% of people in Europe (source). For local councils and businesses looking to light a space, this might be an inevitable sacrifice for safe and usable outdoor facilities. However, there are ways to light effectively whilst preserving the darkness of the night.
Solareye is one of the UK’s leading suppliers of high quality outdoor lighting. Our solar ground lights and our handy Bat Hat device have been put to good use in all sorts of outdoor spaces, from National Parks to cycle ways to campuses and much more!
In this blog, we explain everything you need to know about lighting for dark skies.
What is meant by the term ‘dark skies’?
The spread of urbanisation across the globe has meant fewer and fewer places on earth are untouched by artificial light, and most seemingly dark skies have some lightness.
Light pollution affects our environment in various ways: locally as a result of the light trespass of a single light, or on a larger scale through sky glow. Whilst some sky glow is natural, human-made sky glow refers to the phenomenon of artificial lightning being scattered by dust and gas in the atmosphere, reducing the contrast of celestial objects and creating faint illumination at all times.
Dark skies are places where these effects are minimal, and the night sky is relatively free from the interference of artificial light. These places have a high quality of darkness, with an increased number of starts visible at night.
Why are dark skies important?
Dark skies are vital for protecting wildlife and keeping ecosystems in balance. The spread of artificial light across the world is having numerous impacts on a local and global scale. That’s why any lighting project should take the time to question its potential impact on nearby dark skies.
Artificial Lighting at Night (ALAN) can disrupt the rhythms and behaviours of many nocturnal species, including bats, moths, beetles, and some species of bees. ALAN can reduce rates of nocturnal pollination by 62% (source) and this phenomenon is only going to become more severe. ALAN also impacts bats in various ways, delaying their emergence from roosts and changing their feeding behaviour. Without dark corridors, bats are unable to travel between feeding grounds, and some light averse species will even encounter the so-called ‘vacuum effect’ where their prey is more attracted to well-lit areas.
Sleep and health
The omnipresence of ALAN is altering our circadian rhythms, disturbing sleep cycles and impacting hormones, immune systems, and overall health. Not only that, but a lack of sleep has an impact on mental health and stress, and may reduce life expectancy. We all know that getting outside in the sunlight is essential for our physical and mental health – but we need darkness too.
Finally, lights need energy to function. That means areas with large quantities of ALAN will have increased rates of electricity consumption and carbon emissions, and contribute to the climate crisis. If you’re concerned about the carbon footprint of your project, a great alternative is to opt for dark sky friendly lighting that is LED and solar powered. These types of lights use less energy and don’t require electricity from the National Grid to function, but charge themselves up during the day.
What is a dark sky reserve?
The International Dark Sky Association officially recognises certain areas that are naturally dark at night and free of light pollution as either Dark Sky Reserve status or Dark Sky Parks. They define a Dark Sky Reserve as: “a public or private land possessing an exceptional or distinguished quality of starry nights and nocturnal environment”. A reserve usually consists of a naturally dark sky area and a peripheral zone that protects the darkness at the core. In the UK, the following National Parks are dark sky reserves: Exmoor, the Brecon Beacons, Moore’s Reserve, Snowdonia, the North York Moors and the Yorkshire Dales. Northumberland is said to have the highest quality of dark skies, and has been designated as an International Dark Sky Park.
What is dark sky friendly lighting?
Dark sky friendly lighting is any lighting scheme that provides humans with the illumination they need to go about their lives safely and comfortably, without disturbing nearby wildlife and with the smallest contribution to light pollution possible. Even if you don’t live near a dark sky reserve, it’s still important to light with the quality of night in mind. Lighting that is dark sky friendly will be conscious of light pollution at every stage of the project, and the scheme will be designed with the protection of darkness in mind.
How to light for dark skies – dark sky lighting guidelines
Here are some questions you should ask yourself when lighting an outdoor space.
Is the lighting necessary in this area?
Outdoor lighting should only be implemented where it is necessary for public safety and comfort. If the purpose of your project is mainly aesthetic, you should question whether it is important enough to compromise the quality of the dark sky – nothing is more beautiful than the stars, after all!
If it is necessary, where and when is it needed most?
Think about the spacing of your lights. Light clutter is a category of light pollution, and it refers to excessive groups of lights that can actually cause glare and reduce visibility. Moreover, you should make sure your scheme is actually effective by lighting the things that need to be lit (like pathways, bike shelters, etc) and nothing else. Finally, make sure the lights are only illuminating at the precise time they are needed. Proximity sensors can be a great solution to this!
Is the brightness suitable to the need?
If you must light a space, how bright does it need to be? Dark sky friendly lighting should be kept at below 500 lumens if possible, with precise directionality that ideally channels the light downward. This is because horizontal light travels the furthest through the atmosphere.
Is the light at the correct colour temperature?
Colour temperature is important. Cooler temperatures have been shown to produce more sky glow and have the most significant impact on wildlife. This is thought to be because insects are more attracted to it. That’s why the International Dark Sky Association recommends you choose LEDs with a warm temperature of 3000 Kelvins or lower if you can.
High quality dark sky friendly lighting
At Solareye, we supply a range of eco-friendly solar LED lights to local authorities and businesses. We also help conservation areas light their spaces consciously using our Bat Hat – this handy device can minimise upwards light spillage by 98%!