Use the chart below with the Light Pollution maps to guage the quality of your night skies where you live.
The column labeled "Naked-eye Limiting Magnitude" indicates the dimmest stars visible under each class of light pollution. The larger the magnitude number is, the dimmer the star is. Each whole number represents a factor of 5 in brightness. In other words, a magnitude 5 star appears five times brighter than a magnitude 6 star, while a magnitude 4 star appears ten times brighter than a magnitude 6 star.
|Class||Color Key||Naked-eye Limiting Magnitude||Sky Description||Milky Way||Astronomical Objects||Zodiacal Light / Constellations||Airglow and Clouds||Night Time Scene|
|1||7.6 - 8.0||Excellent, truly dark-skies.||MW shows great detail and light from the Scorpio / Sagittarius region casts obvious shadows on the ground.||M33 (the Pinwheel Galaxy) is a obvious object.||Zodiacal light has an obvious color and can stretch across the entire sky.||Bluish airglow is visible near the horizon and clouds appear as dark blobs againt the backdrop of the stars.||The brightness of Jupiter and Venus is annoying to night vision. Ground objects are barely lit and trees and hills are dark.|
|2||7.1 - 7.5||Typical, truly dark skies.||Summer MW shouws great detail and has veined appearance.||M33 is visible with direct vision, as are many globular clusters.||Zodiacal light bright enough to cast weak shadows after dusk and has an apparent color.||Airglow may be weakly apparent and clouds still appear as dark blobs.||Ground is mostly dark, but objects projecting into the sky are discernible.|
|3||6.6 - 7.0||Rural sky.||MW still appears complex, dark voids and bright patches and meandering outline are all visible.||Brightest Globular Clusters are distinct, but M33 is only visible with averted vision. M31 (the Andromeda Galaxy) is obviously visible.||Zodical light is striking in Spring and Autumn, extending 60 degrees above the horizon.||Airglow is not visible and clouds are faintly illuminated, except at the zenith.||Some light pollution eveidnet along the horizon. Ground objects are vaguely apparent.|
|4||6.1 - 6.5||Rural / suburban transition.||Only well above the horizon does the MW reveal any structure. Fine details are lost.||M33 is a difficult object, even with averted vision. M31 is still readily visible.||Zodiacal light is clearly evident, but extends less than 45 degrees after dusk.||Clouds are faintly illuminated except at the zenith.||Light pollution domes are obviouse in several directions. Sky is noticeably brighter than the terrain.|
|5||5.6 - 6.0||Suburban sky.||MW appears washed out overhead and is lost completely near the horizon.||The oval of M31 is detectable, as is the glow in the Orion Nebula.||Only nints of zodiacal light in Spring and Autumn.||Clouds are noticibly brighter than the sky, even at the zenith.||Light pollution domes are obviouse to casual observers. Ground objects are partly lit.|
|6||5.1 - 5.5||Bright, suburban sky.||MW only apparent overhead and appears broken as fianter parts are lost to sky glow.||M31 is detectable only as a faint smudge; Orion Nebula is seldom glimpsed.||Zodiacal light is not visible. Constellations are seen and not lost against a starry sky.||Clouds anywhere in the sky appear fairly bright as they reflect back light.||Sky from horizon to 35 degrees glows with grayish color. Ground is well lit.|
|7||4.6 - 5.0||Suburban / urban transition.||MW is totally invisible or nearly so.||M31 and the Beehive Cluster are rarely glimpsed.||The brighter constellations are easily recognizable.||Clouds are brilliantly lit.||Entire sky background appears washed out, with a grayish or yellowish color.|
|8||4.1 - 4.5||City sky.||Not visible at all.||The Pleiades Cluster is visible, but very few other objects can be detected.||Dimmer constellations lack key stars.||Clouds are brilliantly lit.||Entire sky background has an orangish glow and it is bright enough to read at night.|
|9||4.0 at best||Inner city sky.||Not visible at all.||Only the Pleiades Cluster is visible to all but the most experienced observers.||Only the brightest constellations are discernable and they are missing stars.||Clouds are brilliantly lit.||Entire sky background has a broight glow, even at the zenith.|