|
Color
|
Artificial / Natural
Sky Brightness
|
Sky Brightness
mags / sq arcsec
V Band
|
Bortle Scale
approx
|
Description (Descriptions are approximate. Your sky may vary.)
|
|
|
< 0.01
|
>21.6
|
1
|
Gegenschein visible. Zodiacal light annoyingly
bright. Rising milkyway confuses some into thinking it's dawn. Limiting
magnitude 7.6 to 8.0 for people with exceptional vision.
|
|
|
0.01 to 0.11
|
21.6 to 21.5
|
2
|
Faint shadows cast by milkyway visible on white
objects. Clouds are black holes in the sky. No light domes. The milky way has
faint extentions making it 50 degrees thick. Limiting magntiude 7.1 to 7.5.
|
|
|
0.11 to 0.33
|
21.5 to 21.3
|
3
|
Low light domes (10 to 15 degrees) on horizon. M33
easy with averted vision. M15 is naked eye. Milky way shows bulge into
Ophiuchus. Limiting magnitude 6.6 to 7.0.
|
|
|
0.33 to 1.0
|
21.3 to 20.8
|
4
|
Zodiacal light seen on best nights. Milkyway shows
much dark lane structure with beginnings of faint bulge into Ophiuchus. M33
difficult even when above 50 degrees. Limiting magnitude about 6.2 to 6.5.
|
|
|
1.0 to 3.0
|
20.8 to 20.1
|
4.5
|
Some dark lanes in milkyway but no bulge into
Ophiuchus. Washed out milkyway visible near horizon. Zodiacal light very
rare. Light domes up to 45 degrees. Limiting magnitude about 5.9 to 6.2.
|
|
|
3.0 to 9.0
|
20.1 to 19.1
|
5
|
Milkyway washed out at zenith and invisible at
horizon. Many light domes. Clouds are brighter than sky. M31 easily visible.
Limiting magnitude about 5.6 to 5.9.
|
|
|
9.0 to 27.0
|
19.1 to 18.0
|
6 or 7
|
Milkyway at best very faint at zenith. M31 difficult
and indestinct. Sky is grey up to 35 degrees. Limiting magntidue 5.0 to 5.5.
|
|
|
>27.0
|
<18.0
|
8 or 9
|
Entire sky is grayish or brighter. Familliar
constellations are missing stars. Fainter constellations are absent. Less
than 20 stars visible over 30 degrees elevation in brigher areas. Limiting
magntude from 3 to 4. Most people don't look up.
|
