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2. Fresnel lens - Wikipedia

   en.wikipedia.org/wiki/Fresnel_lens

   First-order rotating catadioptric Fresnel lens, dated 1870, displayed at the Musée national de la Marine, Paris.In this case the dioptric prisms (inside the bronze rings) and catadioptric prisms (outside) are arranged to concentrate the light from the central lamp into four revolving beams, seen by sailors as four flashes per revolution.

3. Hooper Island Light - Wikipedia

   en.wikipedia.org/wiki/Hooper_Island_Light

   In 1976 the original fourth-order Fresnel lens was stolen, and it was replaced with a solar-power lamp. [3] The lighthouse was added to the National Register of Historic Places on December 2, 2002, as Hooper Island Light Station. The structure was officially turned over to the U.S. Lighthouse Society in June 2009, but the light remains active.

4. Hillsboro Inlet Light - Wikipedia

   en.wikipedia.org/wiki/Hillsboro_Inlet_Light

   The lighthouse and buildings are little altered from their original construction in 1907. [2] In the second half of the 20th century, this inlet became an increasingly busy waterway. Hillsboro Inlet Light is considered one of the most powerful lights in the world with a beam that can be seen for 28 nautical miles (52 km; 32 mi). [Note 3] [10]

5. Aerobeacon - Wikipedia

   en.wikipedia.org/wiki/Aerobeacon

   DCB-224 - Two Harbors Light. The model DCB-224 is a high-power spotlight designed and built by Carlisle & Finch. [1] Originally intended for use as an aerodrome beacon, it was also widely used in marine lighthouses. Depending on the type of bulb installed, the beam could be seen for 18 to 26 nautical miles (33 to 48 km).

6. Middle Bay Light - Wikipedia

   en.wikipedia.org/wiki/Middle_Bay_Light

   white lighthouse: Power source: solar power Operator: Alabama Historical Commission [1] Heritage: National Register of Historic Places listed place Light; Focal height: 48 feet (15 m) Lens: Fourth order Fresnel lens (1885), 155 mm solar-powered lens (current) Range: 4 nmi (7.4 km; 4.6 mi) Characteristic: Fl R 6s., bell struck by machinery every ...

7. Harbor of Refuge Light - Wikipedia

   en.wikipedia.org/wiki/Harbor_of_Refuge_Light

   As a backup, there is a 250-mm lantern operated by solar power, though its visibility is only 9 miles (14 km). Lastly, the fog signal is an FA/232 and also operated by solar power, emitting 2 blasts every 30 seconds. The lighthouse was automated in 1973 and is still an active aid to navigation.