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