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Photographer's Note

This photograph is from the top of the St. Augustine Lighthouse, in St. Augustine, Florida. St. Augustine is America’s oldest city, founded in 1565 by the Spanish. This lighthouse was completed in 1824 and is Florida’s first lighthouse. It stands 165 feet tall (50.3 meters).

Although my camera is pointed almost vertically skyward, note that through the Fresnel lens one can see the entire horizon.

Brent Reeves
Westminster, California

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The Fresnel Lens
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The specialized lens used in the St. Augustine Lighthouse was invented in 1822 by a French scientist, Augustine Fresnel, (pronounced Fruh-nel).

Consisting of hand-cut glass prisms in the shape of a beehive, the prisms are mathematically arranged to capture up to 70% of the light from the lamp. The rays of light are bent, or refracted, by the prisms and collected into a steady horizontal sheet of brilliant light. As the lens rotates around the lamp, curved sections or flash panels called “bulls-eyes: break up the beam and create the lighthouse’s characteristic night signature.

Fresnel lenses were originally divided into six orders or sizes. The St. Augustine light is the largest lens, a first order, that has three bulls-eyes and is approximately nine fee tall. It was made in St. Gobain, near Paris, France. Its beam can be seen nineteen to twenty-five nautical miles.

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