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Astronomical seeing
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In astronomy, seeing is the degradation of the image of an astronomical object due to turbulence in the atmosphere of Earth that may become visible as blurring, twinkling or variable distortion. The origin of this effect is rapidly changing variations of the optical refractive index along the light path from the object to the detector. Seeing is a major limitation to the angular resolution in astronomical observations with telescopes that would otherwise be limited through diffraction by the size of the telescope aperture. Today, many large scientific ground-based optical telescopes include adaptive optics to overcome seeing.
Astronomical observatories are generally situated on mountaintops, as the air at ground level is usually more convective. A light wind bringing stable
Astronomical observatories are generally situated on mountaintops, as the air at ground level is usually more convective. A light wind bringing stable air from high above the clouds and ocean generally provides the best seeing conditions (telescope shown: NOT).
Astronomers can make use of an artificial star by shining a powerful laser to correct for the blurring caused by the atmosphere.
Astronomers can make use of an artificial star by shining a powerful laser to correct for the blurring caused by the atmosphere.
This amateur lucky imaging stack using the best of 1800 frames of Jupiter captured using a relatively small telescope approaches the theoretical maxim
This amateur lucky imaging stack using the best of 1800 frames of Jupiter captured using a relatively small telescope approaches the theoretical maximum resolution for the telescope, rather than being limited by seeing.
Speckle imaging
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Speckle imaging comprises a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add method and the speckle interferometry methods. These techniques can dramatically increase the resolution of ground-based telescopes, but are limited to bright targets.
Lucky imaging images of Jupiter at 5 µm, using stacks of individual Gemini Observatory frames each with a relatively long 309-msec exposure time, illu
Lucky imaging images of Jupiter at 5 µm, using stacks of individual Gemini Observatory frames each with a relatively long 309-msec exposure time, illustrate the principle that coherence time τ0 increases with wavelength.