🔍 Key Concepts

• Sidelight sectors: A red sidelight shows from dead ahead to 22.5° abaft the port beam (Port = left side of the vessel). • The bearing you see (NW 315°) is the direction from you to the other vessel, not the vessel’s heading. • Think about which way the other vessel must be pointed so that you can see its port (red) side from your position.

💭 Think About

• Draw a simple compass rose and mark your own position at the center. Put the other vessel at bearing 315° (NW). From that point, sketch the vessel and its port (left) side. • Ask: if I am looking toward the vessel’s port side, what general direction must that vessel be heading along the compass (roughly toward N, S, E, or W)? • Compare each answer choice by imagining the vessel’s bow pointing that way and decide: from which of those headings would I be able to see the red (port) light from my position at SE (135°) relative to the vessel?

✅ Before You Answer

• Confirm that red = port (left) side and it is visible from dead ahead to 22.5° abaft the port beam. • Make sure you’re treating 315° as your bearing to the vessel, not the vessel’s course line. • For each possible heading, check whether an observer located at the vessel’s southeast quadrant (relative bearing about 135° from the vessel) would see the port side or the starboard (green) side.