Coastal Skipper and Yachtmaster Quiz · Position fixing
On a clear night this light is just dipping on the horizon. Using the table, how far away is it?
On the left, a night view of a single white light sitting exactly on the sea horizon, with the chart description Fl 10s 30m 20M and a note: your height of eye, 2 m. On the right, a table of the distance of the horizon. Height 2 m: 2.9 miles. Height 3 m: 3.6 miles. Height 30 m: 11.4 miles. Height 40 m: 13.2 miles.
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14.3 miles. A light dips when it sits on your horizon. Add the distance of the horizon for your height of eye (2 m: 2.9 miles) to the distance for the height of the light (30 m: 11.4 miles): 14.3 miles. The 20M on the chart is how far the light is bright enough to be seen, not when it clears the horizon.
