On the Water: Flying blind

摘要

In last month's column about interior lighting, I focused on how lighting "temperature" affects sleep cycles and how choosing the right type of bulb can improve your sleep. Sleep, of course, is very important, but at some point you must wake up and start standing watch. It's called a "watch" for good reason. Namely because you must rely on your eyes to see things, both directly via the naked eye or by using binoculars, or indirectly via radar and AIS-enabled navigation chart plotters. Either way, you must be able to actually see, and see well, when you start the watch. And how are we able to see at night? Cells in our eyes called rods and cones allow us to see in the "dark." But we are only able to do this after the eyes adapt to widely varying levels of reduced light. This is a gradual process that takes about 20 to 30 minutes. That is when we reach what I describe as "functional night vision." This continues to improve at a slower rate for several hours before reaching peak capability. Our eyes can't adapt to complete darkness, the absence of all light, as when in a cave.