Clause 9 Horizontal sectors

(1) In the forward direction, sidelights as fitted on the vessel must show the minimum required intensities. The intensities must decrease to reach practical cut-off between 1 degree and 3 degrees outside the prescribed sectors.

(2) For sternlights, masthead lights, and, at 22.5 degrees abaft the beam, sidelights the following provisions apply—

(a) the minimum required intensities must be maintained over the arc of the horizon up to 5 degrees within the limits of the sectors prescribed in rule 22.21; and

(b) from 5 degrees within the prescribed sectors, the intensity may decrease by 50 percent up to the prescribed limits. It must decrease steadily to reach practical cut-off at not more than 5 degrees outside the prescribed sectors.

(3) All-round lights must be located so as to not be obscured by masts, topmasts or structures within angular sectors of more than 6 degrees,

EXCEPT anchor lights prescribed in rule 22.30, which need not be placed at an impracticable height above the hull.

If it is not practicable to comply with this paragraph by exhibiting only one all-round light, two all-round lights must be used. They must be suitably positioned or screened so that they appear, as far as practicable, as one light at a distance of one mile.