Skyglow

sky glowartificial skyglowcity lights reflecting upwards into the skiesglowlight pollutionoutshinespristine night skies
Skyglow (or sky glow) is the diffuse luminance of the night sky, apart from discrete light sources such as the Moon and visible individual stars.wikipedia
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Light pollution

light-pollutedglarelight
It is a commonly noticed aspect of light pollution.
Specific categories of light pollution include light trespass, over-illumination, glare, light clutter, and skyglow.

Night sky

night skiessky''' of the Earthsky of Earth
Skyglow (or sky glow) is the diffuse luminance of the night sky, apart from discrete light sources such as the Moon and visible individual stars.
Optical filters and modifications to light fixtures can help to alleviate this problem, but for optimal views, both professional and amateur astronomers seek locations far from urban skyglow.

Sky quality meter

Amateurs also increasingly use Sky Quality Meters (SQM) that measure in astronomical photometric units of visual (Johnson V) magnitudes per square arcsecond.
It is used, typically by amateur astronomers, to quantify the skyglow aspect of light pollution and uses units of "magnitudes per square arcsecond" favored by astronomers.

International Dark-Sky Association

International Dark SkyIDAInternational Dark Sky Park
Much discussion in the lighting industry and even by some dark-sky advocacy organizations (e.g. International Dark-Sky Association) of the sky glow consequences of replacing the currently prevalent high-pressure sodium roadway lighting systems with white LEDs neglects critical issues of human visual spectral sensitivity, or focuses exclusively on white LED light sources, or focuses concerns narrowly on the blue portion (
Light that shines into the eyes is called glare and light shining into the night sky above the horizon causes skyglow.

Light-emitting diode

LEDLEDslight emitting diodes
Predominantly because of this effect, white light sources such as metal halide, fluorescent, or white LED can produce as much as 3.3 times the visual sky glow brightness of the currently most-common high-pressure sodium lamp, and up to eight times the brightness of low-pressure sodium or amber Aluminium gallium indium phosphide LED.
Light pollution: Because white LEDs emit more short wavelength light than sources such as high-pressure sodium vapor lamps, the increased blue and green sensitivity of scotopic vision means that white LEDs used in outdoor lighting cause substantially more sky glow.

Dark-sky movement

dark skiesdark-skyDark Sky
Dark-sky movement
The movement started with professional and amateur astronomers alarmed that nocturnal skyglow from urban areas was blotting out the sight of stars.

Commission for Dark Skies

Campaign for Dark Skies (CfDS)
The campaign was founded in 1989 by amateur astronomers as a sub-section of the BAA specialising in combatting skyglow.

Luminance

cd/m 2 brightnessluminous
Skyglow (or sky glow) is the diffuse luminance of the night sky, apart from discrete light sources such as the Moon and visible individual stars.

Moon

lunarthe MoonLuna
Skyglow (or sky glow) is the diffuse luminance of the night sky, apart from discrete light sources such as the Moon and visible individual stars.

Zodiacal light

zodiacal dustfalse dawnzodiacal band
While usually referring to sky luminance arising from artificial lighting, skyglow may also involve any nighttime sources of diffuse light, including natural ones like the zodiacal light, starlight, and airglow.

Star, Russia

starstellarstars
While usually referring to sky luminance arising from artificial lighting, skyglow may also involve any nighttime sources of diffuse light, including natural ones like the zodiacal light, starlight, and airglow.

Airglow

air glowair glow phenomenonnightglow
While usually referring to sky luminance arising from artificial lighting, skyglow may also involve any nighttime sources of diffuse light, including natural ones like the zodiacal light, starlight, and airglow.

Gas lighting

gas lampgaslightgas light
In the context of light pollution, skyglow arises from the use of artificial light sources, including electrical (or rarely gas) lighting used for illumination and advertisement, and from gas flares.

Lighting

illuminationartificial lightartificial lighting
In the context of light pollution, skyglow arises from the use of artificial light sources, including electrical (or rarely gas) lighting used for illumination and advertisement, and from gas flares.

Gas flare

flaringflareflare stack
In the context of light pollution, skyglow arises from the use of artificial light sources, including electrical (or rarely gas) lighting used for illumination and advertisement, and from gas flares.

Signage

signsignssignboard
Light used for all purposes in the outdoor environment contributes to skyglow, by sometimes avoidable aspects such as poor shielding of fixtures, and through at least partially unavoidable aspects such as unshielded signage and reflection from intentionally illuminated surfaces.

Cloud

cloudscloud formationcloudy
Skyglow is significantly amplified by the presence of snow, and within and near urban areas when clouds are present.

Rayleigh scattering

scatteredscatteringscatter
There are two kinds of light scattering that lead to sky glow: scattering from molecules such as N 2 and O 2 (called Rayleigh scattering), and that from aerosols, described by Mie theory.

Aerosol

aerosolsaerodynamic diameteratomization
There are two kinds of light scattering that lead to sky glow: scattering from molecules such as N 2 and O 2 (called Rayleigh scattering), and that from aerosols, described by Mie theory.

Mie scattering

Mieelectromagnetic plane wave scatteringLorenz-Mie
There are two kinds of light scattering that lead to sky glow: scattering from molecules such as N 2 and O 2 (called Rayleigh scattering), and that from aerosols, described by Mie theory.

Extinction (astronomy)

extinctionextinction factorinterstellar extinction
Though the shorter wavelengths suffer increased scattering, this increased scattering also gives rise to increased extinction: the effects approximately balance when the observation point is near the light source.

Bortle scale

dark suburban skiessuitably dark skiesbright enough
Amateur astronomers have used the Bortle Dark-Sky Scale to measure skyglow ever since it was published in Sky & Telescope magazine in February 2001.

Sky & Telescope

Sky and TelescopeS&TSky & Telescope (''S&T'')
Amateur astronomers have used the Bortle Dark-Sky Scale to measure skyglow ever since it was published in Sky & Telescope magazine in February 2001.

UBV photometric system

V bandVJohnson
Amateurs also increasingly use Sky Quality Meters (SQM) that measure in astronomical photometric units of visual (Johnson V) magnitudes per square arcsecond.

Charge-coupled device

CCDCCDsCCD camera
All-sky maps of skyglow brightness are produced with professional-grade imaging cameras with CCD detectors and using stars as calibration sources.