Down another level, down past the Rule list, down through the power-driven vessel rule, down to some definitions.
A quick guide to Navigation light definitions
Where are the definitions for Navigation lights?
Section C of the COLREGS, Rule 21.
Here are those definitions condensed down to some easy to remember facts.
What is a masthead light?
- White light
- Placed over the fore and aft centerline of the vessel showing an unbroken light over an arc of the horizon of 225 degrees
- So fixed as to show the light from right ahead to 22.5 degrees abaft the beam on either side of the vessel
What are Sidelights?
- Green light on the starboard side and a red light on the port side
- Each showing an unbroken light over an arc of the horizon of 112.5 degrees
- So fixed as to show the light from right ahead to 22.5 degrees abaft the beam on its respective side.
In a vessel of less than 20 meters in length the sidelights may be combined in one lantern carried on the fore and aft center-line of the vessel.
When did the Red and Green sidelights come into use?
In 1848 the UK issued regulations requiring steam vessels to display red and green sidelights as well as a white masthead light. This was a follow on from an act of 1846 that became the basis of the current IMO COLREGS.
What is a Sternlight?
- White light
- Placed as nearly as practicable at the stern
- Showing an unbroken light over an arc of the horizon of 135 degrees
- So fixed as to show the light 67.5 degrees from right aft on each side of the vessel
What is a Towing light?
- Yellow light
- Same characteristics as the sternlight
What is an all-round light?
- A light Showing an unbroken light over an arc of the horizon of 360 degrees
What is a Flashing light?
- A light flashing at regular intervals at a frequency of 120 flashes or more per minute
Why are the arcs of navigation not given in rounded numbers of degrees?
The arcs of navigation lights are based on the traditional mariners compass. In this each ‘point’ is 1/32 of a circle, which is 11.25 degrees. The change in arch between Masthead lights/Sidelights and the sternlight occures at 2 points abaft the beam, that is 22.5 degrees.
The Navigation Light Definitions and the Rest of The COLREGS
Two vessel situations are defined within the Rules by the aspects of their navigation lights; a crossing situation is implied by being neither of these.
A vessel overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft her beam, that is, in such a position that at night she would be able to see only the sternlight of that vessel but neither of her sidelights.
Head on (Power-driven vessels)-Rule 14
A head on situation exists when a vessel sees the other ahead or nearly ahead and by night she could see the masthead lights of the other in a line or nearly in a line and/or both sidelights, and by day she observes the corresponding aspect of the other vessel.
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