Rule 21 Definitions
a. Masthead light means a white light placed over the fore-and-aft centerline of the vessel showing an unbroken light over an arc of the horizon of 225° and so fixed as to show the light from right ahead to 22.5° abaft the beam on either side of the vessel.
b.
| Sidelights means a 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° and so fixed as to show the light from right ahead to 22.5° abaft the beam on its respective side. |
In a vessel of less than 20 m in length the sidelights may be combined in one lantern carried on the fore-and-aft centreline of the vessel.
c. Sternlight means a white light placed as nearly as practicable at the stern ii showing an unbroken light over an arc of the horizon of 135° and so fixed as to show the light 67.5° from right aft on each side of the vessel.
d. Towing light means a yellow light having the same characteristics as the sternlight defined in paragraph (c) of this Rule.
e. All-round light means a light showing an unbroken light over an arc of the horizon of 360°.
f. Flashing light means a light flashing at regular intervals at a frequency of 120 flashes or more per minute.
There is a mistake in part b, its written “arc of the horizontal of 112.5°” instead of “arc of the horizon of 112.5°”
Appreciate you pointing it out! have fixed the typo, thanks!