Nautical twilight

From AMS Glossary
Jump to: navigation, search


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.

Personal tools
Namespaces
Variants