April 2, 2007 in Keepers Log, Questions for the Keeper

Question for the keeper: the light at night

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Does the light in the tower bother you at night?

If I suffer sleep-deprivation and insomnia, it’s not because of the flashing beacon in the lighthouse tower.  I barely notice that it’s on. To be sure, the light is bright and visible for at least four nautical miles.  However, it is difficult to see for an observer standing directly beneath the tower. How is this so? The lamp shines through a Fresnel lens (pronounced fre-NELL). The lens looks like a series of stacked prisms in a “bee-hive” configuration, which is lighter weight and uses less materials than a conventional spherical lens. Invented by Frenchman Augustin-Jean Fresnel in the early 1800s, the lens magnifies the light and focuses it into a beam which shines out but not down. A tugboat captain or river pilot can easily see the light for navigating the river, but I cannot see enough light to navigate around furniture on my way to the bathroom at night.

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