Twinkling

Under scintillation (from Latin scintillare: " twinkle, flicker " ) is understood in astronomy a seemingly changing brightness of a star, which is caused by light refraction in the Earth's atmosphere.

Formation

This quick and apparent brightness change is caused because the refractive index of the atmosphere is locally changed slightly and become easily distracted the star's light by atmospheric turbulence. This effect is comparable to the fact that the base of the swimming pool due to the waves on the surface will not be uniformly illuminated by the sun.

An important prerequisite for this effect, that stars are point-like objects even in large telescopes. Sun, moon and the planets show no scintillations, as they are also recognizable on earth as extended objects and therefore the fluctuations average out over the extent of the object. However, even if the latter objects lower image sharpness is achieved by the effect, as technically ( ie, from the look, the footage or the resolution of the CCD sensor used ) would be possible.

Determination and prevention

When photographing or other longer-term measurements of the stars makes scintillation due to the exposure time thus apparent that the star appears larger due to its ever- changing light position on the recording, as it actually is. This effect is known in astronomy seeing. For surface objects of the effect leads to a blurred photographic recording visually the object appears " waft " to.

One way to compensate for the scintillation, is the use of active or adaptive optics, as for some time is possible in reflecting telescopes. Another option is to build the telescopes in locations with very smooth air, and / or in high mountain regions, as has been done by the European Southern Observatory. From the outset, you can avoid atmospheric effects by placing the telescope in a vacuum. The most famous example is the Hubble Space Telescope.

Also digital image processing can reduce image noise by scintillation by numerous individual recordings are each very short exposure time, for example, from a digital video camera, overlaid and digitally sharpened. Useless pictures are automatically rejected by the software and combines the useful individual pictures into a detailed final image.

Similarly, the faults can be expected out by two light frequencies close together to be analyzed undergo a slightly different refraction.