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Sailing resources · Navigation & seamanship
Sailboat navigation lights:
know the colors and the arcs.
What can another boater see when they look toward your boat? Learn the light patterns that help you recognize a vessel’s orientation after dark.
See how the lights fit together.
An arc of visibility is the horizontal angle over which a light can be seen. This diagram looks down on the boat, with the bow pointing up.
Under engine power
The standard arrangement shown adds a white masthead light to the sidelights and sternlight. This applies when the engine is propelling the boat, even with sails set.
- Port sidelight · red112.5°
- Starboard sidelight · green112.5°
- Sternlight · white135°
- Masthead light · white225°
A standard separate-light arrangement is shown. Permitted configurations depend on vessel size and the applicable rules.
Four lights. Four useful reference points.
Port sidelight
112.5°Red, from directly ahead to 22.5° behind the beam on the port side.
Starboard sidelight
112.5°Green, from directly ahead to 22.5° behind the beam on the starboard side.
Sternlight
135°White, covering the rear: 67.5° to each side of directly astern.
Masthead light
225°White, covering the forward sector and extending 22.5° behind each beam.
“Abaft the beam” made simple.
Abeam is directly out to either side of the boat, 90° from the bow.
Abaft means toward the stern. The sidelights continue 22.5° beyond the beam.
Remember: left and right refer to the boat’s port and starboard sides when facing its bow.
Use the whole picture.
Practice identifying lights before you need to interpret them on a dark, busy waterway. Keep a proper lookout and consider the vessel’s movement and the surrounding traffic.
A light pattern is a clue. It does not, by itself, establish collision risk or tell you which vessel must keep clear.
Common navigation-light questions
Does a sailboat show a white masthead light under sail?
Under sail alone, it normally shows sidelights and a sternlight. A white masthead light belongs to the power-driven arrangement shown above. Do not confuse a masthead light with a tricolor sailing lantern located near the top of the mast.
What changes when the engine propels the boat?
The boat is power-driven, even if its sails are set. Select “Under engine power” above to see the standard separate-light arrangement.
Can a small boat use an all-round white light?
Under Rule 23, a power-driven vessel under 12 meters may use an all-round white light and sidelights instead of separate masthead and sternlights. An all-round light covers 360°.
Is the arc the same as the light’s visibility distance?
No. The arc describes direction and is measured in degrees. Visibility distance is measured in nautical miles and is addressed separately in Rule 22.
Put your knowledge into practice
Learn to sail with confidence.
Build your sailing and seamanship skills with Lake St. Clair Sailing School in Harrison Township, Michigan.
Lambrecht Marina
31300 North River Road
Harrison Township, MI 48045
Reference: U.S. Coast Guard Navigation Rules, especially Rules 3, 5, 7 and 21–25. This page explains the basic light sectors; it is not a complete guide to every vessel type or operating condition.
