Glossary |
NELM - Naked Eye Limiting Magnitude |
updated: 2025-04-29 |
from: Naked eye Limiting Magniture (Wikipedia)
Theoretically, in a typical dark sky, the dark adapted human eye would see the about 5,600 stars brighter than +6m[6] while in perfect dark sky conditions about 45,000 stars brighter than +8m might be visible.[4] In practice, the atmospheric extinction and dust reduces this number somewhat. In the center of a city, where the naked-eye limiting magnitude due to extreme amounts of light pollution can be as low as 2m, as few as 50 stars are visible. Colors can be seen but this is limited by the fact that the eye uses rods instead of cones to view fainter stars.
Limiting magnitudes with F = 2 (from: Limiting magnitude (Wikipedia)
|
SQM 18.5 |
SQM 19.5 |
SQM 20.5 |
SQM 21.5 |
|
5.0 |
5.3 |
5.7 |
6.0 |
where F is a "field factor" specific to the observer and viewing situation will lie between about 1.4 and 2.4, with F = 2 being typical.
See:
- Limiting magnitude (Wikipedia)
- Naked eye Limiting Magniture (Wikipedia)
- SQM Sky Quality (in this guide)
- Weather Planning (in this guide)
- Rating Skies by SQM (Cloudy Nights)
- Bortle Scale, SQM and NELM (Wikipedia)
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