* Astronomy

Averted vision is a technique for viewing faint objects which uses peripheral vision. It involves not looking directly at the object, but looking a little off to the side, while continuing to concentrate on the object. This subject is discussed in the popular astronomy literature but only a few rigorous studies have been done quantifying the effect. However, the technique is based on well-known properties regarding the structure of the eye.
It is claimed this technique is most useful to astronomers for viewing large but faint nebulae and star clusters. By developing the technique, some observers report a gain of up to three or four magnitudes (15:1 to 40:1).
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Example:

NGC 6826 (also known as Caldwell 15) is a planetary nebula located in the constellation Cygnus. It is commonly referred to as the "blinking planetary", although many other nebulae exhibit such "blinking". When viewed through a small telescope, the brightness of the central star overwhelms the eye when viewed directly, obscuring the surrounding nebula. However, it can be viewed well in the peripheral vision (averted vision), which causes it to "blink" in and out of view as the observer's eye wanders.
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