Definition of Sidelights
Sidelights are the red and green navigation lights visible head on and from the side on a boat that is underway at night (from sunset to sunrise). They shine directly ahead in an unbroken arc of 112.5° on either side of the boat and are only visible to approaching vessels.
The two colors of sidelights indicate the side of the boat they’re on:
- Red navigation light: Denotes the port or left side of the boat
- Green navigation light: Indicates the starboard or right side of the boat
Going back to the light angle, in order to achieve an unbroken arc of the horizon of 112.5°, each side light shines dead ahead to 22.5° abaft the beam (behind the widest part of the boat).
Here’s an illustration to help visualize this:
Another determining factor of sidelights is the size and type of boat, let’s break down these requirements in the table below.
|Boat Length In Feet
|Side Light Required
|Visibility Distance Of Light In Nautical Mile
|Sailboat (under sail)
|Under 23 ft
|Sidelights recommended but not required
|Sidelights separate or a bi-colored combination light
|Alternatively, tri-color light (red, green, white) on top of the masthead, with the colored lights shining forward
|Over 65 ft
|Sidelights must be separated
|Powered boat or sailboat using motor
|Under 23 ft
|Bi-colored combination light if available
|Under 165 ft
|Must show separated sidelights
In the table below is a selection of the sidelights offered by Apex Lighting.
Example of Sidelights in a Sentence
"The system of red on the left and green on the right found in boat sidelights can also be found on buoys."
Synonyms: port and starboard lights, combination lights
Related Terms for Sidelights