Lighting the Way

When it comes to lighthouses, lots of folks have lots of questions:

  1. Do they really need these things anymore?
  2. Does it still work? 
  3. What time does the light come on?

The answer to all three is a resounding “yes”!

You see, navigational lights along our nation’s coastlines are just as important for ship captains and mariners as runway and airport lights are for airline pilots. Just imagine telling airline pilots that they don’t need those runway lights because they have all of those instruments in their cockpits. The truth is, we still use our eyes more than any other of our five senses. Ship captains train for a very long time to be able to navigate a vessel in and around dangerous inlets and waterways and rely on coastal lights to tell them the same thing that their instruments are telling them. Just imagine if their instruments stopped working?

So does it still work? Yes! The St. Augustine Lighthouse still functions as a private aid to navigation for the U.S. Coast Guard and is the navigational beacon for St. Augustine, Florida. It really is simply a reference point along the coast telling ships where they are. Beginning in 1789, the U.S. Lighthouse Service eventually built one large navigational beacon (lighthouse), every sixty miles, on every coast of America. The purpose is so that ships can stay well offshore in deep water where they know they are safe, and every sixty miles there is a light telling them their exact position along the coast. Smaller buoys and lights are used to mark inlets and channels. The focal plane of the light needs to be approximately 160 feet above sea level so that the light is visible many miles out to sea. In the southeast United States where the land is very low and flat, many tall towers had to be built to get the light to this level as opposed to a location that has a 130 foot bluff.  In that location you would only need a 30 foot tall lighthouse to reach 160 feet like the lighthouse at Split Rock, Minnesota on Lake Superior for example. Some lighthouses can have a focal plane of closer to 200 feet above sea level, like Cape Hatteras, North Carolina and Heceta Head, Oregon.  

Each light has different characteristics so you tell which one you are seeing. The “daymark” is simply a physical description of the lighthouse structure from the sea. But many of the tall towers looked the same and were thus assigned a special mark or fancy paint job so you can identify them more easily. Our daymark is black and white spiral stripes with a red lantern on top. At night, each light has a different flash pattern, or “nightmark”, so you can easily identify them after dark. The St. Augustine Lighthouse has a “30-second fixed flash.” This means that the light is visible all of the time at night, and it also flashes every thirty seconds. No other lighthouse has this “nightmark.” Each light’s distinguishing characteristics are published for ship captains in the U.S. Coast Guard’s Aids to Navigation (ATON) guide as well as in books and computer programs.

Even though we still have keepers here at the Lighthouse, our Lighthouse is automated. An electric motor turns our first-order Fresnel lens to create the flash every 30 seconds while a photo cell on the west side of the tower turns the light on when the sun sets and off after the sun rises. We keepers ensure that the automated systems are working and the original lens rotation mechanism is well oiled and maintained.

P.S.  Our Lighthouse even changes its own lightbulb! More on that in another entry.

Post contributed by Rick Cain, Director of Museum Services Division