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Tricks Astronomers use to see Stars Best
by Bryan Schaaf

Rest: Get some rest before going out to observe the stars. A brief nap can help your eyes relax and later perform better in the dark. Avoiding very bright lights or television in the evening before leaving home helps, too.

Dark Adaptation: Once you are at the observing location, look at the night sky. At first you might not see much, but as your eyes adapt to the dark you will notice many more stars. It takes up to an hour for your eyes to become dark adapted and that means you will see light that's 200 times dimmer. Your dark adaptation can be ruined almost instantly with any stray light, so avoid lights to protect your night vision.

Averted Vision: Eyes are very sophisticated. Each eye has a sensor array called a retina. Inside the center of the retina are sensors called cones. Around the cones on the periphery of the eye are rods. Cones are great for sensing colors and fine detail, but they are poor for detecting faint light. Rods are great for detecting dim light, but fail at sensing colors and details. Rods provide a wide angle of vision even at night. Astronomers use this knowledge to optimize what can be seen.

Instead of looking straight AT an object, look to the SIDE out the corner of the eye. The rods will allow you to detect a faint object in the telescope view that otherwise might be missed completely. This is called averted vision.

Image Scanning and Induced Motion: When viewing a telescope image sometimes the object or objects, such as a galaxy cluster, is too faint to see even using averted vision. It often helps to move your vision around in the field randomly. Sometimes this method will cause a faint object to suddenly appear in the periphery of vision. This can also be achieved by gently tapping the telescope tube to induce a motion of the image. Motion can often bring out the faint, nearly invisible objects, much like a deer in the woods, for instance. When a deer stands still it's colors can blend into the surrounding vegetation, but it can often be detected when it moves.

All of the above tricks to see the stars best have to do with the ability of the brain and eyes to work together. Your eyes' sophisticated lens system sends an upside down image to the sensors of the retina, similar to the function of a camera or telescope. Your brain inverts the image for you. Also, the brain tends to correct other defects that the lens sends to your retina. The eye-brain combination can be trained to see very dim light or detect subtle differences in light level or color. The more observing you do the more you will see! Patience and practice are the keys that make amateur astronomy fulfilling.

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