130 seamanship secrets
THREE STEPS TO AN INSTANT DANGER BEARING
You can use red sector arcs as danger bearings without having to plot them
on your chart. Follow these three steps.
- Look in the Light List under the Remarks column. Choose the correct
bearing to use as a danger bearing. - Apply variation to the danger bearing.
- Label the danger bearing with the prefi x NLT (not less than) if the
danger lies to starboard. Label the danger bearing NMT (not more
than) if the danger lies to port.
You’re bound northwesterly along the Florida Keys, en route to the Dry Tortugas.
Without plotting, fi nd a danger bearing using the Light List and Rebecca Shoal
Light. The variation is 3 degrees west.
Look at the chart (see illustration on page 129) and note the two dashed arcs
that radiate from the light. One bears to the northwest toward the light and one
to the southwest toward the light. Choose the arc closest to your trackline—in
this case, the arc that bears northwesterly. Turn to your Light List and look up
Rebecca Shoal Light. Look in the Remarks column to fi nd the exact bearing of the
northwesterly arc (302 degree true). Apply variation to convert this to a magnetic
bearing: 302 degrees true + 3 degrees west = 305 degrees magnetic. Th e danger
bearing is NLT 305 degrees magnetic.
While on your trackline, take bearings with your handbearing compass to
the light. As long as those bearings are greater than 305, you are in safe water.
If, at any time, you sight a steady red light, or the bearings fall below 305, turn
south to return to safety.