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Averted vision is a technique for viewing faint objects which involves not looking directly at the object, but looking a little off to the side, while continuing to concentrate on the object. This technique is very useful to astronomers, as it oftentimes allows them to see especially faint or otherwise invisible objects. By developing the technique, some observers report a gain of up to three or four magnitudes. There is some evidence that the technique has been known since ancient times, as it seems to have been reported by Aristotle while observing the star cluster now known as M41. // Headline text HEY!! HOW ARE YOU ALL?? Its nice of you to come read this page. ...
Aristotle (Greek: Aristotélēs) (384 BC – March 7, 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. ...
Open Cluster M41 (also known as Messier Object 41, Messier 41, M41, or NGC 2287) is an open cluster in the Canis Major constellation. ...
A similar technique that employs the same principal 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.
Physiology
In the simplest sense, averted vision works because there are more rods (cells which detect dim light in black and white) slightly off the optical axis of our eyes. The density of the rods usually reaches a maximum around 20 degrees off the center of vision at around 160,000 rod cells per square millimeter. This is a greater density than the peak density of the cones (bright light and color detectors) - on the fovea (the center of vision), which is about 140,000 cells per square millimeter. However, due to the way the cells are connected to the nervous system, the most sensitive portion of the eye is usually 8 to 16 degrees away from the center. This is because the photoreceptor cells closer to the center have more ganglion cells connecting to them, and thus more nerve connections. Normalised absoption spectra of human rod (R) and cone (S,M,L) cells. ...
Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina of the eye which only function in relatively bright light. ...
The fovea, a part of the eye, is a spot located in the center of the macula. ...
A ganglion cell (or sometimes called a gangliocyte) is a type of neuron located in the retina that receives visual information from photoreceptors via various intermediate cells such as bipolar cells, amacrine cells, and horizontal cells. ...
It is also important to note that it also matters whether you avert right or left. The most effective direction is always to the nasal side of the vision. So, for right-eyed observers it is best to shift to the left, and for left-eye observers it is best to shift to the right. 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.
See also Peripheral vision is a part of vision that occurs outside the very center of gaze. ...
The introduction of this article does not provide enough context for readers unfamiliar with the subject. ...
Scotopic vision is the monochromatic vision of the eye in dim light. ...
The Purkinje effect (sometimes called the Purkinje shift, or dark adaptation) is the tendency for the peak sensitivity of the human eye to shift toward the blue end of the color spectrum at low illumination levels. ...
External Links and References - "Just What is Averted Vision, Anyway?"
- Techniques for Good Observing
- M41 possibly recorded by Aristotle
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