Dusk Stages of twilight | Altitude degree | Illuminance lux | Luminance cd/m2 | Lower Limit of Sky Brightness (mag./arcsec2) |
Civil | −6˚ | 3.4 | 1.08 | 12.42m |
Nautical | −12˚ | 8.31 × 10−3 | 2.64 × 10−3 | 19.03m |
Astronomical | −18˚ | 6.52 × 10−4 | 2.08 × 10−4 | 21.79m |