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Diffraction rings

Diffraction rings

The Diffraction rings they are concentric hoops that surround the image of a star when viewed with a telescope. They cannot be eliminated, as produced by the wave motion of light and the construction of the telescope. They are more exaggerated in small instruments.

The light waves interact with each other, reinforcing or canceling each other. Telescopes diffract light in such a way that they form a series of concentric luminous rings around the image of a star. These rings stand out when we look at an object and blur the image. In these circumstances the star will be shown as a small point with one or more diffraction rings around.

With a bad telescope or with atmospheric turbulence they would not be easily appreciated. In a perfect image, the central point, called the Airy disk, contains 84% ​​of the light collected by the opening. The first ring collects 7%, and the rest is distributed in lower intensity rings.

In the nineteenth century the English physicist Lord Rayleigh established limits of resolution. In his opinion, two stars can be resolved if one of them is located in the center of the Airy disc and the other in the first dark ring. The Rayleigh limit is 5.5 arc seconds for every 25mm opening.

Diffraction, in physics, is a phenomenon of wave motion in which a wave of any kind extends after passing along the edge of a solid object or through a narrow slit, instead of moving forward in a straight line.

The expansion of light by diffraction produces a blur that limits the useful magnification capacity of a telescope.


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