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The astronomical seeing conditions at an observatory can be conveniently described by the parameters r 0 and t 0. For telescopes with diameters smaller than r 0 , the resolution of long-exposure images is determined primarily by diffraction and the size of the Airy pattern and thus is inversely proportional to the telescope diameter.
The refractive index of water at 20 °C for visible light is 1.33. [1] The refractive index of normal ice is 1.31 (from List of refractive indices).In general, an index of refraction is a complex number with real and imaginary parts, where the latter indicates the strength of absorption loss at a particular wavelength.
The Sea or the Water is an area of the sky in which many water-related, and few land-related, constellations occur. This may be because the Sun passed through this part of the sky during the rainy season. [1] Most of these constellations are named by Ptolemy: Aquarius the Water-bearer; Capricornus the Sea-goat; Cetus the Whale; Delphinus the ...
They forecast the cloud cover, transparency and astronomical seeing, parameters which are not forecast by civil or aviation forecasts. [1] They forecast hourly data, but are limited to forecasting at most 48 hours into the future. Each individual chart provides data for only a 9 mile radius, and so are essentially point forecasts.
In astronomy, the photosphere of a star is defined as the surface where its optical depth is 2/3. This means that each photon emitted at the photosphere suffers an average of less than one scattering before it reaches the observer.
Diagram showing displacement of the Sun's image at sunrise and sunset Comparison of inferior and superior mirages due to differing air refractive indices, n. Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. [1]
If not specified, a reference to the Fried parameter in astronomy is understood to refer to a path in the vertical direction. When observing at a zenith angle ζ {\displaystyle \zeta } , the line of sight passes through an air column which is sec ζ {\displaystyle \sec \zeta } times longer, producing a greater disturbance in the wavefront ...
In Chinese astronomy, the stream of water flowing from the Water Jar was depicted as the "Army of Yu-Lin" (Yu-lim-kiun or Yulinjun, Hanzi: 羽林君). The name "Yu-lin" means "feathers and forests", referring to the numerous light-footed soldiers from the northern reaches of the empire represented by these faint stars.