Range light

From Wikipedia, the free encyclopedia

Baileys Harbor Range Lights, with the rear light in a house and the front light on a skeleton tower. The red and white striped panel is a daymark designating a range light.^[1]

A range light is a lighthouse designed to serve in tandem with at least one other. The pair (designated the "rear" and "front" lights) indicate, by their alignment, the path of a channel.

According to The American Practical Navigator,
Range lights are light pairs that indicate a specific line of position when they are in line. The higher rear light is placed behind the front light. When the mariner sees the lights vertically in line, he is on the range line. If the front light appears left of the rear light, the observer is to the right of the range line; if the front appears to the right of the rear, the observer is left of the range line.^[2]

Unlike conventional light towers, range lights were sometimes designed to be movable; consequently, their position could be shifted in the event of a change in the sea channel.