How can lighthouses be differentiated at night?⁣ ⁣ By their “characteristic” or nightmark. Their lights may appear to either glow constantly (fixed) or flash at different rates. The Cape Hatteras Lighthouse’s rate is every 7-1/2 seconds, though it has varied over the years. Throughout the centuries, mariners have had lists of lights - tables that list the nation's navigational aids including the lighthouses with their exact positions, their daymarks, and their light characteristics.⁣ ⁣ #FindYour