What is meant by "averted vision technique"?

When viewing through binoculars or telescopes, most deep sky objects look like faint fuzzy blotches of light - at first. The ability of the human eye to see intricate detail even in faint objects is truly impressive if one takes the time to develop the needed observing skills. First and most important is to make sure the observer is DARK ADAPTED. This means setting up in a dark-sky site with no white lights (streetlights, car headlights, porch lights, flashlights) in view. The pupils in the eye take a minimum of 15 minutes to fully dilate and thus adjust to see faint details in the dark. Now you are ready to use AVERTED VISION to discern fine details on astronomical objects. When viewing through the eyepiece, look not only directly at the subject but around the edges or even slightly off to the side. Slowly look back and forth and around it in this manner, and finer details will seem to flicker in out of the "corner of your eye"! This is happening because your peripheral vision is more sensitive to faint light than your direct vision, which is more constantly used. To preserve your night vision, use a red-filtered flashlight to read star maps or find your way around. A similar technique that employs the same principle is called scope rocking, and is done by simply moving the telescope back and forth slightly to move the object around in the field of view. It is also important to note that it also matters whether you avert right or left. The most effective direction is that which places the object on the nasal side of the vision. So, for right-eyed observers it is best to shift to the right, and for left-eye observers it is best to shift to the left. Some people also claim that it is better to avert up instead of down. The best thing to do is practice and find the best location for one's own eyes.