NIGHT VISION

to be a good lookout you've got to be able to see at night that means learning an entirely different way of looking than you use by day in daylight you searched the horizon by looking directly added but to see at night you've got to shift your eyes slightly to look a little above the horizon and here's why the human eye sees by focusing images through its lens system onto its retina which sends those images onto the brain the retina is covered with many nerve endings some of these are sensitive only to bright light but others are sensitive only to very dim light immediately behind the lens is a spot where only nerve endings sensitive to bright light are concentrated so this spot the fovea sees objects most clearly in bright light and in bright light you look directly at objects to see them clearly but when the light is very dim this is actually a blind spot because it has no nerve endings sensitive to dim light objects all around your direct line of vision can be seen because their images fall upon those nerve endings which are sensitive to dim light here's an object on the horizon at night when you look directly at it you can't see it because of that blind spot but by looking slightly above it you can see the object because it's image is formed on your dim light nerve endings so don't look directly at the horizon at night when searching look slightly above it this use of off-center vision is the most important thing to remember in might searching the next point to remember is that it takes time for the ayah to adjust itself from bright light to very dim light if you go directly from a brightly lighted compartment out into the dark you'll find that you're practically blind for a while then as your eyes become adapted they become more and more sensitive to the dim light but it takes about half an hour before they reach their greatest sensitivity and you're really able to see that means that if every look out were to go on watch directly from a bright compartment out into the night the ship would be practically blind for a good part of the first half hour you can prevent this by preparing your eyes for darkness before going on watch those dim light nerve endings of the I can't see anything in red light so you put on special red goggles and dark adapt your eyes before going out by wearing your goggles for half an hour you literally keep your eyes in the dark long enough for them to reach their dim light sensitivity later when you go out in the dark it will take your eyes only a few minutes to reach their full sensitivity but you have to protect your eyes against white light so you use a red lens flashlight if you have to write reports adjust your binoculars or do anything else requiring light all illuminated dials and working lights on your ship are colored red to preserve your dark adaptation and keep the enemy from seeing them if you have to go into a bright compartment from your watch out in the dark you wear your red goggles to protect your eyes against the white light once you've learned to see at night you'll pick up various ways of watching for signs of objects out there in the dark one obvious way is to watch for silhouettes against the moon when it's low on the sky sometimes the reflections from a bright star may be interrupted by the bulk of a shift on certain nights a ship may appear as a dark object against low-lying fog banks or clouds by learning to watch for these signs and others you'll find it possible to pick up objects more quickly to be a good lookout at night you've got to take care of yourself in your eyes that means eating the proper foods it means using your red goggles to adapt your eyes a half hour before going on watch and then protecting them by using only red light to work by it means wearing your red goggles to protect your eyes if you have to go into a lighted area and above all it means learning to see at night by using your off-center vision being a good lookout is a 24-hour responsibility it's your job to be a good lookout by night as well as by day