New York, USA
Lat: 40.71°•Lon: -74.01°
NAUTICAL MARITIME TWILIGHT
11:15 AM
Sea horizon is distinguishable; 57 navigational stars become observable
First Light (Civil Dawn)11:49 AM
Sunrise12:20 PM
Solar Noon04:59 PM
Sunset09:38 PM
Last Light (Civil Dusk)10:09 PM
True Night (Astro Dusk)11:17 PM
Nautical Dawn Calculator (Maritime Horizon)
Sun Ascends Past -12°•Sea Horizon Distinguishability•Sextant Star Sight Window•Marine Navigation Readiness
Calculate the Maritime Horizon Window at Sea
Nautical dawn occurs when the sun rises to 12 degrees below the horizon in the morning. For mariners and navigators, this is a celebrated astronomical moment: the sea horizon first becomes sharp enough to measure with a marine sextant while the navigational stars remain bright in the sky.
Plan celestial sights and maritime passages with accurate -12° solar depression calculations for any coastal port or open ocean coordinate.
How to Use the Nautical Dawn Calculator
1
Enter your vessel coordinates or select a coastal port.
2
Check the exact time when the sun reaches -12° below the horizon.
3
Prepare sextants to shoot celestial navigation stars against the visible sea horizon.
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Frequently Asked Questions
What is nautical dawn?
Nautical dawn is the moment morning twilight begins its nautical stage, occurring when the center of the sun is 12 degrees below the horizon.
Why is nautical dawn important for sailors?
Historically and in modern celestial navigation, sailors require both a visible horizon line and visible stars to measure altitudes with a sextant to determine position.
Can you see well enough to walk without a light at nautical dawn?
Generally no. Terrestrial ground objects are still difficult to discern at nautical dawn, requiring flashlights or artificial lighting.
Ready to Use the Nautical Dawn Calculator?
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