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There are those who claim that this is the age of information. All day long, we are bombarded with information in the form of sight and sound. Much of this information is redundant. We passively watch a television program, which floods us with thousands of images in order to obtain a small amount of information. We do not work to get this information. We do not have to concentrate on the image from the TV set in order to understand what it is telling us. Looking at the sky is very different. There is no redundant information coming to us when we look at the sky. Almost every particle of light coming to us has some importance. The difference between watching television and looking at the sky is similar to that between quickly scanning a long novel and slowly reading a poem.
Of course, there are some objects in the sky that can be seen quite easily. The constellations of Orion and the Big Dipper have so many bright stars that their shapes are always easy to identify. The planets Venus and Jupiter are brighter than any star and are also fairly easy to spot, but after a while the fainter objects such as star clusters and galaxies will begin to draw your attention.
When you start to look at the sky, always spend a few minutes looking at the constellations. First, because they are beautiful and it is always enjoyable to gaze up at their different patterns. Secondly, spotting a few of the constellations will help orient you. I always take at least one quick glance at the ecliptic to see if there are any planets overhead. Most importantly, these few minutes give your eyes a chance to become dark-adapted. Dark-adaptation is the ability of your eyes to see extremely dim objects. Dark-adaptation can take over half an hour to take place complete. Any time your eyes are exposed to a bright light, suddenly faint stars that you were able to see a few minutes previously will disappear and it will take at least a few minutes of darkness before you can see them again. According to the optometrist, Keith P. Bown, pre-exposure to bright sunlight “can affect the eye’s ability to dark adapt for up to several days.” The effect varies from person to person. Mr. Bowen’s solution is not to lock yourself up in the basement during the daylight hours if you have this problem, but to wear during day yellowish lenses that block out the types of light that most affect your dark-adaptation.
There are two types of light sensitive elements within the eye: cones and rods. The cones are sensitive to color and work best in bright light. The rods are most effective in low light conditions. Light adaptation takes place through chemical changes within the rods. Unlike the cones, which are concentrated in the center of the eye, there are almost no rods at the center point. Since the rods are concentrated off center our night vision is best off center. When you are looking a t a group of dim objects, you will be able to see those on the sides better than those in the middle. This is why “averted vision” is so effective when looking at dim objects in the sky. Averted vision works with binoculars, telescope or the naked eye. The idea of averted vision is to direct your eyes slightly away from the object you wish to observe and to look at it from the “corner” of your eye. It sounds harder than it really is. We naturally tend to direct our eyes and our minds to the same spot, especially when we are trying very hard to see it. Nevertheless, it takes only a bit of practice to develop your averted vision and the rewards are well worth the effort. Direct your eyes a little to the left or right of the object you wish to see and at the same time let your mind see the whole scene, not merely the point in space directly ahead. After a while, averted vision will become almost automatic to you as you scan the sky.
There are other factors that can affect your dark-adaptation. Both smoking and drinking can cause deterioration in your sight. Your blood-sugar level is also important. A low level of blood sugar tends to cause a lowering of the eye’s sensitivity. Eating some food or at least a candy bar can counteract this.
Both eyeglasses and contact lenses can be bothersome. Any object between the sky and your eyes, no matter how clear, will absorb some of the precious light from the sky. If you clean your lenses daily, it might as well be just before you go skygazing. If you suffer from near or farsightedness and are using binoculars or a telescope, simply remove your eyeglasses or contacts and use the focusing mechanism on the instrument to compensate for your vision. One of the problems of hard contact lenses is that they can block off oxygen from the cornea, the membrane in front of the lens of the eye, and cause it to become less transparent. Bown advises removal of hard contact lenses for up to an hour before skygazing in order to let oxygen reach the cornea if they have been worn for a long period beforehand.
Your eyes can easily tire, particularly after staring through a pair of binoculars for half an hour while searching for some comet that you are sure has to be at that spot. The best thing to relieve that type of eye strain is to stretch your legs, blink your eyes a few times and spend a few minutes looking at a constellation in a different area of the sky. A bright constellation may be the best eye tonic.