Mobile Apps

Dark Sky meter App (iPhones)
The Award-winning Dark Sky Meter by DDQ helps you measure the night sky brightness with the press of a button. Get instant information about the night sky quality and contribute to creating a global map of sky darkness. See our Measuring Light Pollution page for more information.

Loss of the Night App (iPhones and Androids)
The Loss of the Night app turns your eyes into a light meter, allowing you to become a citizen scientist and report how bright the night sky is where you live! See our Measuring Light Pollution page.

F.lux (available for Mac OS/X, Windows, Linx, iPhones and iPads)
f.lux is a colour temperature app that makes the colour of your computer’s display adapt to the time of day, warm at night and like sunlight during the day. It makes your computer screen look like the room you’re in, all the time. When the sun sets, it makes your computer look like your indoor lights. In the morning, it makes things look like sunlight again.

Lux (Android phones free or paid versions)
Lux intelligently adjusts the brightness of your display based on the environment you’re in. It’s also able to adjust the screen temperature of your display automatically to make it appropriate for night usage. At sunset, you can have Lux automatically warm your display and switch to your Night profile. If you’re an astronomer, you can enable astronomer mode to cut out harsh white light.

Twilight (for smartphones or tablets)
The Twilight app makes your device screen adapt to the time of the day. It filters the flux of blue light emitted by your phone or tablet after sunset and protects your eyes with a soft and pleasant red filter. The filter intensity is smoothly adjusted to the sun cycle based on your local sunset and sunrise times.

Dark-Sky Activities to Enjoy at Home

Here are some great resources to enjoy the night sky, whether it be in your garden, through your living room window, or on a computer screen.  

Family Arts & Crafts

Contribute to Night Sky Citizen Science

Familiarize yourself with your night sky and contribute to important citizen science projects:

  • Globe at Night is your go-to international citizen-science program that people can do from their backyards at no cost.
  • Dark Sky Citizen Science Program offers three citizen science programs to measure how light impacts our view of the night sky as well as three projects to measure the diversity of life on Earth.
  • The Satellite Streak Watcher citizen science programs or on SciStarter
  • Loss of the Night as well as on a blog on SciStarter 
  • Dark Sky Meter is a phone app that acts like a Sky Quality Meter.

Virtual Tours

Can’t get out into the dark? Check out these options for exploring the night sky with virtual reality:

Press Release Example

This is an example of a post that has its category set to ‘Press Release’ and how it shows up in the press release section. Any new post can be set as ‘Press Release’ as well as any other categories.

My Neighbour’s Lighting

When a neighbour (or the council) installs outdoor lighting which also lights up your home, or shines through your windows, this is called “light trespass”. We don’t get involved in neighbourhood disputes BUT we can give you some useful information to help solve this problem in a simple, professional and friendly way. The first step is that your neighbour probably doesn’t realise there is a problem so its a good idea to have a friendly chat to begin with and maybe show them what their light looks like from your point of view. (A little goodwill goes a long way.)

Many people believe that more and brighter lighting makes us safer, but there is no solid evidence suggesting that’s true. In fact, glare from unshielded lights can create shadows where criminals hide. And bright lighting can even make it easier for criminals to work.

So, how do you talk to your neighbour about this situation?

(If the light trespass is from streetlights, see our Bad Streetlights page.)

Practical Actions:

  • Make friends, not enemies. Your neighbours probably don’t even realize their lighting is bothersome.
  • Stay positive and don’t argue. Be tactful and understanding about your neighbour’s right to light their property and to feel secure.
  • Suggest alternatives to their current fixture. Ask them to move the light, shield it, or add a motion sensor so it’s activated only when needed. Offer to help get this done.
  • Be helpful. Talking to your neighbour is a great opportunity to be an advocate for good lighting. There are many reasons to use dark sky-friendly lighting.
  • Have a list of shielded light fixtures to suggest as alternatives to your neighbour’s current lighting. Use our Fixture Seal of Approval database to find dark sky-friendly fixtures and devices.
  • Remember that everyone wants the same thing: a chance to relax in his or her own environment. Work together to create an atmosphere that benefits the community
  • Write a letter, take a picture of how the light impacts your home and garden. You may find it useful to put your thoughts on paper. We have provided a Sample Letter to Your Neighbor to get you started. Additionally, here is a recorded presentation on this subject.
Awful, cheap "security" light as sold by DIY Stores. Do not use.
Awful, cheap “security” light as sold by DIY Stores. Very bright, 5000 Kelvin, usually pointed upwards. Replace as soon as you can! Image: Bob Mizon

Outdoor Sports Lighting

LED lighted soccer facility located adjacent to a residential neighbourhood. The photo was taken approximately 150 meters from the field edge.

There has been a significant increase in the number of outdoor sports areas built in urban and suburban neighbourhoods; at schools, parks, and outdoor play areas. The excessive amount of light associated with these is a nuisance for neighbourhoods and creates significant environmental impacts.

Historically it has been difficult to control the light “lumens” to the level needed for dark-sky compliance because light fixtures used older bulbs lamp sources (incandescent, metal halide, high-pressure sodium, etc.). These bulbs and the reflectors housing them are too large to effectively shape and focus the light onto the field of play, causing light spillage, glare, and impacting nocturnal wildlife and the surrounding communities.

very bright uplighting glare from badly installed sports lighting.
Very bright uplighting glare from badly installed sports lighting (near Stonehenge). Image: CfDS
These two photos were taken at the same facility, on opposite sides of the access road. (Left) Pointed toward the athletic field. (Right) Pointed toward the neighbourhood.

Recent advances in LED lighting technology offer lighting designers the opportunity to develop lighting sources strong enough to light the field of play, BUT small enough to be effectively shielded. With this technology, recreational sports lighting can be configured and designed to be effectively shielded to illuminate the field of play and minimize or eliminate glare and light trespass.

The IDA Technical Committee released the criteria for IDA Community-Friendly Outdoor Sports Lighting in March 2018:

  1. Minimises neighbourhood lighting nuisances by greatly reducing the allowable spill and glare disruption. Quantitative pass/fail thresholds are established.
  2. Manages high angle glare, thus off-site light trespass and sky glow effects due to direct and reflected light are dramatically lower.
  3. Mandates curfew requirements, thus mitigating neighbourhood nuisance factors and sky glow effects which benefit flora/fauna and night sky enthusiasts’ and astronomers’ views of the night skies during peak viewing periods.
  4. Limits the class of play to recreational levels, thus discouraging over-lighting practices.
  5. Promotes “Best Lighting” practices that minimize lumen densities, which reduces energy consumption, benefiting the environment at large.
Bad Sports Lighting in West England showing two pictures one with the lights on and terrible glare, and the other with lights off and a good dark sky.
Bad Sports Lighting in West England, turned on or off.

Now sports lighting designers can apply to IDA-UK for certification of their designs. Fields in full compliance with the IDA Criteria for Community-Friendly Outdoor Sports Lighting (PDF) can then receive recognition from IDA and an award plaque, recognising the minimisation of light pollution.

LED Practical Guide

The light-emitting diode (LED) is transforming the way we light our cities and towns, offering a once-in-a-lifetime chance to radically improve how we use energy and our outdoor spaces at night. With this opportunity comes an obligation to manage these changes responsibly and sustainably. The stakes are high and the potential rewards great, but outcomes depend critically on policymakers and the public having access to reliable information. IDA developed this document to provide planners, lighting designers, and public officials with an overview of the most important aspects of LED lighting and the choices and challenges involved in its municipal implementation.

What is LED?

LEDs use solid-state technology to convert electricity into light. Put simply, LEDs are very small light bulbs that fit into an electrical circuit. Unlike traditional incandescent bulbs, they don’t have a filament that burns out, and they don’t get very warm. Initially, LEDs only emitted red, yellow, or green light, but now white LEDs are widely available. Early LEDs were also energy-inefficient and emitted relatively little light, but due to technological advances LED efficiency and light output have doubled about every three years. Because of their improved quality and falling prices, LEDs are now replacing conventional high-intensity discharge (HID) lamp types for outdoor lighting in communities around the world.

Why Adopt This Technology?

The improved energy efficiency of LEDs means that coupled with modern luminaire design, these lights allow for lower illumination levels without compromising safety. LEDs help lower carbon emissions by reducing the demand for electricity, which is still largely generated by burning fossil fuels. Another LED benefit is better control over the colour content of light. Manufacturers now produce LEDs with “warm” colour qualities at high energy efficiency, rendering old arguments about the perceived inefficiency of warm white LEDs moot. These same LED options also provide accurate colour rendition without emitting excessive amounts of potentially harmful blue light (see below).

Relative to other outdoor lamps, LEDs are thought to be extremely long-lived. When switched on, LEDs are instantly at full brightness, unlike HID lamps which have a significant time delay to begin emitting light. LEDs also have very low minimum electricity thresholds to produce light, meaning they can be dimmed to much lower illumination levels when less light is needed and resulting in further energy savings.

Blue Light Can Be Bad

New technical capabilities often come with unanticipated challenges. Most white LED lighting has significant levels of potentially harmful blue light. IDA published a report in 2010 detailing the known and suspected hazards of blue-rich white light sources.[i] In the years since scientific evidence has coalesced around its conclusions. Blue-rich white light sources are known to increase glare and compromise human vision, especially in the ageing eye.[ii],[iii] These lights create potential road safety problems for motorists and pedestrians alike. In natural settings, blue light at night has been shown to adversely affect wildlife behaviour and reproduction when exposed to it at the wrong time of day.[iv],[v] This is particularly true in cities, which are often stopover points for migratory species such as birds.

Concerns about blue light reach far beyond biology. Outdoor lighting with strong blue content is likely to worsen skyglow because it has a significantly larger geographic reach than lighting consisting of less blue. According to the 2016 “New World Atlas of Artificial Night Sky Brightness” street lighting and outdoor lighting retrofits using 4000-kelvin white LED lamps could result in a factor of 2.5 increase in light pollution.[vi] Given that the rate of increase of lighting as seen from Earth orbit is about 2 percent per year,[vii] it is all the more important to address this problem.


The promise of cheaper outdoor lighting based on electricity and maintenance savings from LED conversion should be weighed against other factors, such as the blue light content of white LEDs. Blue-rich white LEDs are among the most efficient light sources in terms of the conversion of electricity to light and therefore have the lowest electricity cost to produce a given amount of light compared to “warmer,” less efficient white LED lamps. At the same time, we should make every effort to diminish or eliminate blue light emissions and exposure after dark.

Product Selection Considerations

Choosing LED products for outdoor lighting applications involves a series of considerations and tradeoffs. These include:

  • Luminous Efficacy (Watts-to-lumens): How much light is produced per input Watt of electricity? 
  • Lumen Output: How much light is produced relative to the amount required for a particular task? When replacing existing fixtures, it is important to use the only level of illumination needed and not to adopt unneeded increases in brightness.
  • Correlated Color Temperature (CCT): Does the light have a “warm” (lower Kelvin value) or “cool” (higher Kelvin value) quality?
  • Color Rendering Index(CRI): How accurately does the light render colours to the human eye? A high CRI is not needed for all situations. The need for good colour rendition should be considered relative to the lighting application in question.
  • Adaptive Control Integration: Does the lighting make use of adaptive controls such as dimmers, timers, and/or motion sensors? These controls are the wave of the future in outdoor lighting and achieve additional energy savings, improve light source efficacy and increase visual task performance. It is important to build in the ability to make use of adaptive controls during the adoption of designs for new lighting installations, even if they will not immediately be implemented.
  • Lumen Depreciation: How robust is the lamp against efficacy loss over time? Manufacturers typically quote “L70,” the expected use time until a bulb reaches 70% of its initial light output.

Closely related to all these factors is expense: How much do LED replacement solutions cost? The price of commercial LED lighting products continues to drop, and capital cost recovery times for new LED street light installations, once 10 years or more, are now typically less than two years and continue to decline. As barriers to implementation fall, LED is gaining momentum as the lighting technology of choice in both new outdoor installations and existing replace-on-failure installations. Already many white LED options are available on the outdoor lighting market and that number will only rise in the future.

IDA Recommends

IDA and the Illuminating Engineering Society (IES) have developed a joint document that outlines excellent lighting practices with their “Five Principles for Responsible Outdoor Lighting.” These should always be considered as part of any lighting installation.

If the light is deemed useful and necessary, follow these guidelines to prevent, or when that’s not possible, minimize light pollution:

  • Useful – All lights should have a clear purpose.
    Before installing or replacing a light, determine if the light is needed. Consider how the use of light will impact the area, including wildlife and the environment. Consider using reflective paints or self-luminous markers for signs, curbs, and steps to reduce the need for permanently installed outdoor lighting.
  • Targeted – Light should be directed only to where needed.
    Use shielding and careful aiming to target the direction of the light beam so that it points downward and does not spill beyond where it is needed.
  • Low Light Levels – Light should be no brighter than necessary.
    Use the lowest light level required. Be mindful of surface conditions as some surfaces may reflect more light into the night sky than intended.
  • Controlled– Light should be used only when it is useful.
    Use controls such as timers or motion detectors to ensure that light is available when it is needed, dimmed when possible, and turned off when not needed.
  • Colour – Use warmer colour lights where possible.
    Limit the amount of shorter wavelength (blue-violet) light to the least amount needed. Light where you need it, when you need it, in the amount needed, and no more.

In addition, give the community a chance to have a say in what they will be living with for a generation, with test installations for soliciting public input and feedback. Printable LED Information Handout (PDF)


[i] “Visibility, Environmental, and Astronomical Issues Associated with Blue-Rich White Outdoor Lighting” (PDF:

[ii] Lin, Y., Liu, Y., Sun, Y., Zhu, X., Lai, J., & Heynderickx, I. (2014). Model predicting discomfort glare caused by LED road lights. Optics Express, 22(15), 18056.

[iii] Sweater-Hickcox, K., Narendran, N., Bullough, J., & Freyssinier, J. (2013). Effect of different coloured luminous surrounds on LED discomfort glare perception. Lighting Research & Technology, 45(4), 464–475.

[iv] Bennie, J., Davies, T. W., Cruse, D., & Gaston, K. J. (2016). Ecological effects of artificial light at night on wild plants. Journal of Ecology, 104(3), 611–620.

[v] Hori, M., & Suzuki, A. (2017). Lethal effect of blue light on strawberry leaf beetle, Galerucella grisescens (Coleoptera: Chrysomelidae). Scientific Reports, 7(1).

[vi] Falchi, F., Cinzano, P., Duriscoe, D., Kyba, C. C. M., Elvidge, C. D., Baugh, K., Portnov, B. A., Rybnikova, N. A., & Furgoni, R. (2016). The new world atlas of artificial night sky brightness. Science Advances, 2(6), e1600377.

[vii] Kyba, C. C. M., Kuester, T., Sánchez de Miguel, A., Baugh, K., Jechow, A., Hölker, F., Bennie, J., Elvidge, C. D., Gaston, K. J., & Guanter, L. (2017). Artificially lit surface of Earth at night increasing in radiance and extent. Science Advances, 3(11), e1701528.

Lighting Laws & Policy

Lighting regulations are an important tool for setting reasonable limits on light pollution. IDA-UK supports cities to adopt and enforce policies that call for shielded, downward-pointing lighting, lighting timers and other sensible controls. Doing so conserves energy, lowers costs and carbon emissions and helps to minimize glare, light trespass and skyglow.

Our Policy Goals are to Update the Existing Legislation

From the APPG For Dark Skies Policy Plan:

The existing legal framework regulating light pollution is derived from statute and therefore can only be amended by Parliament. New legislation is therefore likely to be necessary to truly protect the UK’s dark skies and night-time landscape.

1.    Strengthen the National Planning Policy Framework: for the first time ever, make extensive specific reference to the control of obtrusive light in the National Planning Policy Framework.

2.    Expand the scope of the planning permission process: introduce regulations for exterior lighting that are similar to those which currently cover advertisements.

3.    Strengthen Statutory Nuisance Provisions: remove exemptions to give local authorities a more effective method of preventing nuisance lighting. ”   

APPG For Dark Skies
  • For a detailed look at UK laws, head over to the CfDS webpage on lighting law by clicking here.
  • For a more in-depth look at how the APPG for Dark Skies want to change existing legislation click here.
  • The governments light pollution planning page is here.

The IDA/IES Model Lighting Ordinance

In 2011 IDA and the Illuminating Engineering Society of North America approved the Model Lighting Ordinance (MLO), an outdoor lighting template designed to help councils develop outdoor lighting standards that reduce glare, light trespass, and skyglow. The MLO is a valuable guide for environmentally responsible outdoor lighting in the USA that has applications in the UK as well. It encourages the broad adoption of comprehensive outdoor lighting ordinances without burdening cities with the extensive staff time and resources needed to develop their own codes.

The MLO offers several innovations to outdoor lighting regulation, including the use of lighting zones to classify land use with appropriate lighting levels for each. The MLO also makes use of the “BUG” (Backlight, Uplight and Glare) classification of outdoor lighting fixtures to ensure that only well-shielded fixtures are used. The MLO is a useful tool that the IDA-UK uses to support similar lighting changes across the United Kingdom.

What to Consider Regarding LEDs

As many communities move to embrace LED lighting, the landscape of nighttime lighting is changing rapidly and dramatically. While some industry representatives tout these new fixtures as being “dark sky friendly,” that’s not usually the case.

Communities considering switching out their older streetlights for LEDs should read:
Printable LED Information Handout (PDF)
Visibility, Environmental, and Astronomical Issues Associated with Blue-Rich White Outdoor Lighting (PDF)

Bad Streetlights

A bad example: All these streetlights spill light in all directions and up into the sky. With no shielding, the exposed globes cause glare, making it difficult to see. Photo by Jim Richardson

Sometimes streetlights are badly designed or installed incorrectly and end up shining lights into your home and garden, This is known as light trespass.

If the bad lighting is from a neighbour’s light, see our My Neighbour’s Lighting webpage.

If the light trespass comes from a street light, it’s unlikely that you’ll be able to get the offending streetlights removed but polite yet firm action may help you get your peace of mind and dark skies back.

a street showing bad streetlights that produce glare, light trespass and uplighting.
Bad streetlights that produce glare, light trespass and uplighting. Image: Chris Baddiley

It’s probably the council who are responsible for streetlights and there’s usually a department dedicated just to street lighting. You should be able to call your council switchboard to find out who to email or speak to, and sometimes the council website will have a form you can fill in to make a complaint. However you do it, explain how your quality of life has been diminished by the streetlight/s and request a “full cutoff shield” or a “house-side shield” for the most offending lights.

light from streetlights pours into a house on the staircase through a window
Light Trespass from an unshielded streetlight into a house. Image: CfDS

Shields for streetlights are available from most streetlight manufacturers, although your council may initially tell you otherwise. Be persistent, you are simply requesting that the light shining in your direction be directed toward the ground where it belongs. If this approach fails or your written requests go unanswered, contact your local councilor or MP and request action and support for your position, but be diplomatic. Many politicians might feel proud about lighting up the streets, making people feel safe, and deterring crime in spite of the fact that this isn’t the case and that the evidence linking brighter lighting to less crime is inconclusive at best.

By tactfully and persistently making your case about the effects of light trespass on you and your property, eventually, you should prevail. You could offer to pay for the shields, but only as a last resort.

Home Lighting

How many exterior lights do you have around your home or property? Are you sure? Have you carefully considered each fixture’s need, function, or design? Are you minimizing light pollution in your own backyard? If not, you’re not alone. Unfortunately, much of our outdoor residential lighting is inefficient, poorly installed, or altogether unnecessary. 

These misguided lighting practices contribute to light pollution, disruption of wildlife, impact human health, and waste money and energy. As of 2018, the average American wastes 41-103 pounds of CO2 per year on excessive residential outdoor lighting alone (1). Across the country, this amounts to at least $1.4 to $3.5 billion wasted each year, unnecessarily lighting the dark around our homes. Our analysis also indicates that these numbers may grow as Americans are likely consuming more exterior lighting than ever before (2). 

Here’s the bright side: Light pollution is completely reversible.


Want to protect the night from light pollution? Get started in your own backyard (or front porch, walkway, bedroom window, rooftop – anywhere!) 

Follow this step-by-step guide to conducting an outdoor lighting assessment around your house, apartment building, property line, community centre, or wherever to evaluate the impact of your light on the night. After completing the steps to make your home dark sky friendly, you can download and display a Dark Sky Friendly Home Certificate!  


With responsible lighting practices, it is possible to reduce light pollution and create a beautiful, healthy, and safe lit environment where you live and work. Let’s learn the basics and put them to work. 

Even the simplest actions can make a big difference.
DID YOU KNOW? 20% – 50% of outdoor residential lighting is lost to the night sky, due to poor shielding alone (3).


Did you know? DarkSky works with lighting manufacturers and home retail stores so that you can easily source DarkSky-approved lighting.



So you’ve addressed all your problem lighting, but what about the lighting that is beyond your control? Maybe your neighbour’s lighting is shining in your bedroom window, or your landlord or property manager needs to make changes. Check out these tips for working with your neighbour’s lighting


It’s important that your property is safe and responsibly lit to protect you from potential hazards, support wayfinding, or deter potential crime. But brighter does not equal safer. In fact, too much lighting can have the opposite effect. Learn more about lighting, crime, and safety


Estimates suggest that on average street lighting accounts for about 50% of a city’s total light emissions (4). Learn what you can do about streetlights in your community


Ready for the next step? Learn what you can do to take action today for a better night tomorrow. The universe will thank you. 

A car repair shop replaced its one unshielded fixture with two dark sky friendly fixtures, minimizing light pollution on surrounding trees and focusing lighting on the ground where it is needed, creating a well lit and safer backyard. Photo: Joyce Harman

Lighting For Policy Makers

Why Should Your Town or City Worry about Light Pollution?

Energy Waste and Carbon Emissions

In an average year in the U.S. alone, outdoor lighting uses about 120 terawatt-hours of energy, mostly to illuminate streets and car parks. That’s enough energy to meet New York City’s total electricity needs for two years!

DarkSky International estimates that at least 30 percent of all outdoor lighting in the U.S. alone is wasted, mostly by lights that aren’t shielded. That adds up to $3.3 billion and the release of 21 million tons of carbon dioxide per year! To offset all that carbon dioxide, we’d have to plant 875 million trees annually (see our Light Pollution and Energy Waste page).

Negative Effects on Wildlife

Numerous studies have shown that artificial light at night has numerous negative and deadly effects on many types of wildlife including birds, amphibians, insects and mammals. The evidence and research is also growing to demonstrate that nocturnal pollinators are being hit hard by thoughtless lighting.

What about Crime and Safety?

There is no clear scientific evidence showing that increased outdoor lighting deters crime. While brighter lighting may make us feel safer, poor outdoor lighting can actually reduce our personal safety. A study conducted by the city of Chicago found a correlation between increased crime and brightly lit alleyways. A study prepared by the U.S. National Institute of Justice concluded: “We can have very little confidence that improved lighting prevents crime.”

In fact, glare from bright lights creates shadows where criminals can hide. Some crimes like vandalism and graffiti thrive on lighting. Glare can also be dangerous to pedestrians and drivers. It shines into our eyes, constricting our pupils, which diminishes our ability to adapt to low-light conditions.

A Problem that has Simple Solutions

The good news is that your town can have it all – environmentally responsible lighting that helps keep citizens safe. When lighting is shielded, it’s directed down on the ground where it’s needed, which minimizes glare, light pollution and carbon emissions, and saves money.

Why Outdoor Lighting Policies Matter

Outdoor lighting policies are a great tool for ensuring that towns and cities implement good, safe outdoor lighting. A well-written policy, with proper lighting installed, will save the public money and increase safety. DarkSky International, in collaboration with the Illuminating Engineering Society (IES), created the Model Lighting Ordinance (MLO) to make it easier for municipalities to adopt good lighting plans. This is a USA-based policy but forms a good foundation for policy and legislation in the UK.

LEDs and Outdoor Lighting

Many towns and cities are replacing older, conventional, lighting systems with new, energy-efficient, light-emitting diodes (LEDs). However, energy efficiency is just one piece of the puzzle in improving outdoor lighting at night.

DarkSky International has developed a set of recommendations for towns and cities considering the installation of LED lighting systems. These recommendations take into account a number of important considerations and provide guidance for selecting outdoor lighting that increases energy and cost savings, enhances safety and security, protects wildlife, and preserves the nighttime environment.