What should the conning officer and helmsman be aware of when using a magnetic compass?

The conning officer and helmsman should be particularly aware of how the magnetic compass responds to the ship's own magnetic influences, which is why the compass swing towards the ship is the most pertinent concern. When a vessel operates, the metal components and electronic systems onboard can create magnetic interference, leading to compass deviation. This means that the compass may not point to magnetic north accurately, impacting navigational decisions. Understanding how to compensate for this swing is crucial for maintaining accurate course heading and ensuring safe navigation.

Considering the other aspects, while changing tides can affect navigational depth and the visibility of other vessels pertains to collision avoidance, they do not directly influence the accuracy of the magnetic compass itself. The speed of the ship, though relevant to maneuvering and timing, similarly doesn't directly affect the compass reading. Thus, the primary focus for those navigating must be on the magnetic variables, highlighting the importance of the compass swing towards the ship.