Table 1 Illuminance values calculated from the angular luminance distribution for a clear and overcast night at LakeLab, Germany.

From: Using all-sky differential photometry to investigate how nocturnal clouds darken the night sky in rural areas

 

clear

clouds

horizontal illuminance [mlx]

average (full data)

1.10 ± 0.11

0.68 ± 0.07

northern segment (*)

1.04 ± 0.10

0.51 ± 0.05

SQM (**)

0.92 ± 0.09

0.69 ± 0.07

scalar illuminance [mlx]

average (full data)

2.44 ± 0.24

1.42 ± 0.14

northern segment (*)

2.33 ± 0.23

0.92 ± 0.09

SQM (**)

1.84 ± 0.18

1.38 ± 0.14

Zenith luminance [mcd/m2]

SQM

0.29 ± 0.03

0.22 ± 0.02

DSLR

0.30 ± 0.03

0.21 ± 0.02

  1. (*)Hypothetical value assuming an equal angular luminance distribution for all azimuth angles (**) inferred value assuming a constant luminance for all azimuth and zenith angles. Zenith luminance from SQM and DSLR are given as reference.
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