| 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 |
22.00 to 21.99 |
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. Users of large dobsonian telescopes are very
happy. |
| |
0.01 to 0.11 |
21.99 to 21.89 |
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 |
21.89 to 21.69 |
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 |
21.69 to 21.25 |
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 |
21.25 to 20.49 |
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 |
20.49 to 19.50 |
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 |
19.50 to 18.38 |
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 |
<18.38 |
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. CCD imaging is still possible. But telescopic
visual observation is usually limited to the moon, planets, double stars and variable
stars. |
