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Buoyage

What is an isophase light?

Short answer

An isophase light has equal periods of light and darkness.

On charts, isophase means the light and dark intervals are equal in each cycle. That rhythm helps you distinguish one aid to navigation from another at night.

Sources and scope

Reviewed by Richard Moore on . This answer is scoped to iala region a unless the answer says otherwise; check the current chart, publication, local rules and official operational guidance before acting afloat.

Quick check

What is an isophase light?