Massive Fresnel Lens: Guiding Ships 28 Miles Away
One of the coolest displays of the Great Lakes Shipwreck Museum is the second order fresnel lens . Originally from White Shoal, Michigan, this lens served Lake Michigan for over 75 years, warning sailors of shallow waters. Due to its size and the refracting capabilities of the lens, its light can be seen over 28 miles.
It has 344 separate precision-ground, leaded crystal prisms which are perfectly arranged to refract and magnify a modestly sized light source into an intense beam.
Why is it called a “second order” lens? Starting in 1825, Augustin Fresnel developed a series of 51 lights and lenses for his lighthouse plan. He ordered the lenses by size, with “first order” being the largest.
We’ve seen quite a few fresnel lenses in our travels and this is definitely the largest we’ve seen yet! It is 9 feet in diameter and weighs in at just about 3,500lbs! Because its rotational mechanism works similar to that of a grandfather clock, it must be wound every 2 hours and 18 minutes. Can you imagine being a lighthouse keeper on such a precise schedule?
