🔍 Key Concepts

• Aid to navigation light characteristics (flash, occulting, isophase, etc.) • Difference between an individual flash and a complete light cycle • How light periods are shown in the Light List and on charts

💭 Think About

• When a light has multiple flashes, eclipses (dark times), or groups of flashes, at what point does its pattern "start over"? • Is the period measured from the beginning of one flash to the beginning of the next identical pattern, or just from one flash to the very next visible change? • Look at an example: a light that shows two quick flashes then darkness. What would mariners need to know about its timing to positively identify it?

✅ Before You Answer

• Be clear on the difference between a single flash and a full repeating pattern of that light • Remember that the period includes both lighted and eclipse (dark) intervals in the pattern • Ask: what definition would best allow a navigator to identify a light by timing its full, repeating sequence?