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Fresnel Lens

Fresnel lenses for lighthouses come in 6 primary sizes, called orders. First order lenses are the largest and only used on ocean lighthouses.

Only a few 2nd Order lenses were used on the Great Lakes, with the 4th Order being the most commonly used.

Fresnel Lenses primarily use refraction to capture the light being emitted from the flame or light bulb, then bend the light to focus it into a concentrated beam. Their introduction vastly improved the efficiency of lighthouses worldwide, with a Fresnel Lens being able to make use of as much as 97% of light emitted from the lamp. 

The Kewaunee Pierhead Lighthouse Fresnel Lens is a fifth-order lens. That means it has a height of 21.3 inches, a focal length of approximately 7.5″, and weighs approximately 275 lbs. Its useful visual distance is about 15 miles which is average for a lens of this size. Such a lens would have cost about $950 to make in 1900 which would equate to $35,000 in 2024 currency. (according to the US Lighthouse Society)

The lens was manufactured by Barbier and Fenestre in Paris, France, and installed in the (1889) Front Range light on the North Pier in 1905. When the current lighthouse was placed into service in 1912, the lens was transferred to the new tower.

 

The lens is designed as a fixed lens for 270 degrees of its frame, with the quarter of the frame facing shore as a reflector panel. This reflector panel also doubles as a door, providing the access to the lamp, or in modern time, the electric bulb changer.

Decommissioning the 
Fresnel Lens

On June 6, 2019, the 5th Order Fresnel lenses in the Kewaunee and Algoma Pierhead Lighthouses were decommissioned and replaced with LED lights

Read about the process and see photos and video of the event.

The old lens is now housed in a display case as part of the lighthouse preservation project, and is located at the Kewaunee County Historical Society.

217 Ellis St, Kewaunee

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