ATN PS-40 Operator's Manual page 52

ESTIMATION OF AMBIENT ILLUMINATION LEVEL
Some of usual natural light conditions and corresponding repre-
sentative illumination values are presented in Table C-1.
Standard Natural Light Conditions and Illumination Values
STANDARD NATURAL LIGHT CONDITIONS
Quarter moon
Full moon
Late twilight sky
Twilight sky
Overcast sky in the daytime
C-1
APPENDIX C
Table C-1.
ILLUMINATION VALUE, LUX
0.05
0.30
1.00
10.00
500.00