Averted Vision

[title type=”modern-h2″ align=”center”]Averted Vision[/title]

You’d think that looking through a telescope was easy. When looking for bright objects its easy but if you are trying to pick out faint detail then there is a technique you need to learn that will help you see more. The technique is called ‘averted vision’ and to understand it, we need to learn a little about how the human eye works.

Inside the eye, the things that detect light are split into two types, rods and cones. The cones are great at detecting colour and are found in the centre of the back of the eye (the retina) whilst the rods are good at detecting faint and delicate detail and are found surrounding the cones.

The light we use in every day situations gets focussed onto the cones so we perceive plenty of colour in the world around us. Now the cones are great at detecting colour but to do that there must be plenty of light available. At night and during low levels of light, the cones don’t work well so in these conditions, its the rods that give us all the detail. They’re great at picking up low levels of light but are rubbish at seeing colour. At night, look around you and you will only see limited colour information, that’s the rods at work.

Now the trick for an astronomer looking at a faint object is to send the incoming light onto the rods instead of the cones. How on earth do you do that?! Its not as hard as it sounds. All you do, is shift your attention slightly to the side of the object you are trying to see. The faint light from the object is then focussed on the rods and the object pops into clearer view. Until you get practiced at this ‘averted vision’ you will find yourself instantly switching your gaze straight back at the object, using the cones, and it disappears or at worse, goes very faint again. With practice though, you will be able to study objects in great detail by looking just to the side of them.

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