The Fifth Order Fresnel Lens Seeing The Light

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Application

The Fifth Order lens was used in leading lights, showing the line of a channel, or the entrance to a harbor. It was also used in river navigational lights to mark small shoals and islands in sounds, and to mark breakwaters. Three of the Great Lakes lights fitted with this lens were South Haven, Michigan City and Grand Traverse.

Specifications
Lens height: 21.3".
Focal length:  7.4"
Weight of assembly:  265 to 440 lbs.
Relative brightness (over sixth order): 1.23
Useful range:  Up to 10 nautical miles.
Number in US Lighthouses in 1884: 131
Number in US Lighthouses in 1922:  129 
Oil consumption per hour: 3.15 oz.

References

Annual Report of the Lighthouse Board, 1884
The United States Lighthouse Service
, Dept of Commerce, 1915
Aids to Navigation Manual, US Coast Guard, 1945
Comparative Table of Lens Orders, Mabel A. Baiges, 1988
Letter from Helen & Al Gademsky, 07/02/01

Terry Pepper. This page updated 12/02/2007

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