| 0 |
: |
Rain or other precipitations |
 |
| 1 |
: |
Sky completely cloudy |
| 2 |
: |
Sky mainly cloudy
[In this condition some observations might be possible from time to time] |
| 3 |
: |
Partly cloudy sky
[Cumulus clouds passing over or patchy layers of stratus or cirrus Clouds] |
| 4 |
: |
Sky so hazed over that observing is difficult
[Only the brightness planets and stars are visible] |
| 5 |
: |
Hazy Sky
[Humidity or dust particles are causing reduced visibility] |
| 6 |
: |
Slightly hazy sky |
| 7 |
: |
A typical clear sky in a city
[With some light pollution reducing visibility] |
| 8 |
: |
Suburban clear sky
[Milky Way is visible] |
| 9 |
: |
Very clear sky
[The Milky Way is clearly visible when it is significantly above the horizon] |
| 10 |
: |
Absolutely fantastic sky
[A sky so clear that is velvety blackness is pierced only by myriad stars and the Milky Way] |