Nautical twilight

nautical twilight

The twilight stage during which the sun's unrefracted center is at elevation angles −6° > h₀ > −12°.

During a clear evening's nautical twilight, horizontal illuminance decreases from ∼3.5–2 lux to ∼0.008 lux. At nautical twilight's bright upper limit, the brightest stars are visible and the (ocean) horizon is distinct. At its dark lower limit, the horizon is generally invisible.

INDEX
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
0
1
2
3
4
5
6
7
8
9