Light Pollution Data: Is It Accessible?

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It has harmful effects on human health, wildlife, and the environment. Light pollution is increasing globally, in both developed and developing countries. To monitor this, suitable remote sensing methods are being developed, including the use of satellite data, images taken by astronauts from the international space station, and stratospheric balloons. There are several organisations working to reduce light pollution, such as the U.S.-based International Dark Sky Association (IDA).

Light pollution data sources

Light pollution is a growing global issue, with 80% of the world's population living under light-polluted skies. There are several sources that provide light pollution data, often in the form of interactive maps. Here are some of the key sources:

Interactive Maps

• NASA Blue Marble Navigator: This tool provides a bird's-eye view of light pollution in your town or city. It offers a detailed look at light pollution from a satellite perspective.
• Google Earth Overlay: Created from the "World Atlas" data, this overlay for Google Earth users provides another way to visualize light pollution in specific locations.
• Globe at Night: This interactive light pollution map utilizes data collected by citizen scientists over eight years, offering a unique perspective on global light pollution.
• Lightpollutionmap.info: This website is a mapping application that displays light pollution data over Microsoft Bing base layers (road and hybrid Bing maps). It includes features like SQM/SQC measurements, World Atlas 2015 zenith brightness, and aurora predictions. The application is also available for mobile devices, offering additional features such as offline mode and high DPI basemaps.

Other Sources

• The World Atlas of Artificial Night Sky Brightness: Published in 2016, this groundbreaking atlas provides valuable data and insights into global light pollution. It reveals that 80% of the world's population lives under sky glow, and 99% of people in the US and Europe cannot experience a natural night.
• Scientific Papers: Scientific studies, such as those by Falchi et al. and Kyba et al., offer in-depth analyses and data on light pollution. These papers are often cited as references for light pollution information and can provide detailed insights for specific locations or time periods.

Light pollution data for astrophotography

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It has harmful effects on wildlife, ecosystems, energy, and climate change. Light pollution data can be accessed from various sources, which can be useful for astrophotography.

Sources of Light Pollution Data

• Light Pollution Map: This is a mapping application that displays light pollution-related content over Microsoft Bing base layers (road and hybrid Bing maps). It provides access to VIIRS/DMSP data and other interesting light pollution-related content like SQM/SQC measurements, World Atlas 2015 zenith brightness, aurora prediction, and IAU observatories features.
• NASA Blue Marble Navigator: This tool provides a bird's-eye view of the lights in your town, offering valuable light pollution data for astrophotography planning.
• Globe at Night: This interactive light pollution map is created with eight years of data collected by citizen scientists, providing a community-driven perspective on light pollution levels.
• Clear Outside: This mobile app by First Light Optics helps you determine the Bortle Scale class of your location, indicating the level of light pollution in your area.

Tips for Astrophotography in Light-Polluted Areas

• Use Monochrome Cameras and Quality Narrowband Filters: Monochrome cameras, in combination with narrowband filters, can significantly enhance your astrophotography experience, even in light-polluted areas. Narrowband filters are excellent for capturing emission nebulae, but they may not be as effective for dark nebulae or reflection nebulae.
• ISO and Temperature Considerations: When using a DSLR camera in light-polluted areas, keep your ISO low, preferably around 800, to minimize noise. Additionally, avoid shooting on hot nights, as higher temperatures can increase noise in your images.
• Invest in Filters: Narrowband filters, such as HA, SII, and OIII, are excellent for capturing nebulae. HA filters are particularly effective in fighting light pollution and can be used even during a full moon. However, consider the types of targets you plan to photograph, as some filters may be more or less suitable.
• Pick the Right Targets: When shooting from light-polluted areas, focus on large and bright targets, such as the Lagoon and Triffid Nebulae, which are more likely to yield better results.
• Use Fast Telescopes or Lenses: Opt for fast telescopes (f/5 or lower) or DSLR lenses (f/1.4 or f/1.8) to gather more light in each frame, improving your overall signal-to-noise ratio.
• Utilize Calibration Frames and Dithering: Properly take calibration frames (darks, bias, and flats) to reduce noise. Additionally, dither every 3 frames to minimize noise and improve the accuracy of your images.
• Manage Exposure Time and Histogram: Check your histogram to ensure your images are properly exposed. In light-polluted areas, consider stacking multiple short exposures instead of taking long exposures to balance light levels and reduce noise.

By following these tips and utilizing light pollution data sources, you can improve your astrophotography experience, even in challenging light-polluted environments.

Light pollution maps

There are several light pollution maps available online. One such map is the interactive map created from the "World Atlas of Artificial Night Sky Brightness" data. This map allows users to select different base layers and light pollution years to compare data over time. According to this map, the trend in light pollution is not good for stargazers, with truly dark skies becoming harder to find.

Another light pollution map is available on www.lightpollutionmap.info. This website displays light pollution-related content over Microsoft Bing base layers (road and hybrid Bing maps). It includes overlays such as VIIRS/World Atlas/Clouds/Aurora and a point feature overlay (SQM, SQC, and Observatories). The website also has a mobile application available for a small price, which includes additional features such as offline mode and high DPI basemaps.

NASA also provides light pollution data through its Blue Marble Navigator, which offers a bird's-eye view of the lights in your town. Additionally, Google Earth users can download an overlay created from the "World Atlas" data to visualize light pollution.

These light pollution maps can be valuable tools for those looking to understand and mitigate the effects of light pollution. They can also help stargazers find locations with minimal light pollution to observe the night sky.

Light pollution and human health

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. Research suggests that it can negatively affect human health, increasing the risks of obesity, depression, sleep disorders, diabetes, breast cancer, and more.

Humans have evolved to the rhythms of the natural light/dark cycle of day and night. The proliferation of artificial light at night means most of us no longer experience truly dark nights. Many studies have shown that exposure to artificial light at night negatively affects human health. According to the American Medical Association, "It is estimated that white LED lamps have five times greater impact on circadian sleep rhythms than conventional street lamps."

Like most life on Earth, humans adhere to a circadian rhythm — a sleep-wake pattern that is governed by the natural day/night cycle. This cycle is largely influenced by photoreceptors in the eye that are more sensitive to blue wavelengths of light. It is important for every human to experience outdoor lighting during the day and minimize the amount of light entering their eyes at night to maintain a good circadian cycle.

Night-time exposure to artificial light also suppresses melatonin production, which is needed to keep us healthy. Melatonin has antioxidant properties, induces sleep, boosts the immune system, lowers cholesterol, and helps the functioning of the thyroid, pancreas, ovaries, testes, and adrenal glands. Exposure to any light at night can suppress melatonin, but the photoreceptors in our eyes that drive this suppression are more sensitive to blue light. Unfortunately, most LEDs used for outdoor lighting, as well as computer screens, TVs, and other electronic displays, create abundant blue light.

The bright lights of US cities at night have been connected to poorer human health. While this light affects everyone, research has found that it is non-white, disadvantaged populations that are exposed to a higher level of light at night. These areas are often more densely populated with more structures lit up at night, and fewer streetlights with covers.

Light pollution comes in many forms, including sky glow, light trespass, glare, and over-illumination. Sky glow is the bright halo that appears over urban areas at night, a product of light being scattered by water droplets or particles in the air. Light trespass occurs when unwanted artificial light spills onto an adjacent property. Glare is created by light that shines horizontally, and over-illumination refers to the use of artificial light well beyond what is required for a specific activity.

Light pollution and the environment

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is a side effect of industrial civilization and can come in several forms: light trespass, over-illumination, light clutter, and sky glow. Light trespass occurs when unwanted light escapes from one property into adjacent properties. Over-illumination is the use of excessive light where it isn't needed. Light clutter refers to the redundant clusters of lighting common in urban centres. Sky glow is the collective light pollution found over big cities.

Light pollution has harmful effects on wildlife, ecosystems, and energy and climate change. It disrupts the daily cycle of light and dark that plants and animals rely on to govern life-sustaining behaviours such as reproduction, nourishment, sleep, and protection from predators. For example, artificial lights can disrupt the breeding rituals of frogs and toads, and they can confuse sea turtles, causing them to head towards cities instead of the ocean. Insects are also drawn to artificial lights, which can impact the food sources of birds and other animals.

Light pollution can also negatively impact human health. Disruption of the circadian rhythm has been linked to sleep disorders, depression, hypertension, attention deficit disorder, obesity, diabetes, and heart disease. Exposure to bright light at night can also halt the production of melatonin, which has been correlated with rising rates of breast cancer.

There are several organizations working to reduce light pollution, such as the U.S.-based International Dark Sky Association (IDA). Individuals can also take action by using outdoor lighting only when and where it is needed, ensuring that outdoor lights are properly shielded and directed downwards, and keeping window blinds, shades, and curtains closed at night to keep light inside.

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