128 seamanship secrets
Range Sector Strategy Secrets
It’s 2030 on a summer evening. You’ve plotted a northbound course into
the harbor. The chart shows a powerful range, visible from 5 miles at sea. It
carries a quick flashing lower light and an isophase 6-second upper light. At
3 miles, you still haven’t picked up the range. What’s going on? (For a quick
review on ranges, see Chapter 1, Ranges Lead You to Safety.) If you’ve checked
the Local Notices to Mariners (LNTM) for reports of outages, the next step
is to check the Light List. Take a look at this excerpt from the Light List for
the Fort Sumter range.
Name & Location Position Characteristic Height Range Structure RemarksFORT SUMTER
RANGE FRONT
LIGHT32 45 04 N
79 52 15 WFl W (Day)
Fl W 2 .5s (Night)26
38 5On
skeleton
tower.Visible 0. 5 °each side
of range line.
Lighted throughout 24
hours.
FORT SUMTER
RANGE REAR
LIGHT
3,665 yards, 298. 4 °
from front light.32 45 58 N
79 54 07 WF W (Day)
Iso W 6s (Night)166
170On
skeleton
tower.Visible 0. 5 °each side
of range line.
Lighted throughout 24
hours.Th e Light List will give you more detail than you can get from a chart on ranges for
nighttime navigation.
SEA-CRET TIP
X Avoid confusion by setting up simple signals between the navigator
and the spotlight operator. On power vessels, you may need to send
the spotlight operator forward. Use battery-operated headsets for
quieter, hands-free communications between the spotter on the bow
and the navigator.In the Remarks column for the Fort Sumter range, note that the range is only
visible within a narrow 1-degree arc (i.e.,^1 / 2 degree on each side of the range line).
Large, deep-draft vessels require such precise tolerances to keep from running
aground. In a small boat, you can pick up a range like this by steering a course
90 degrees across the rangeline. Use a slow speed so that you can make a sharp
turn to take you down the range line as soon as it becomes visible.