Atmospheric dispersion is the blurring of the image of a star or planet when a ray of light passes through the Earth’s atmosphere , which manifests itself in the form of a small spectral spot.
It is a special case of dispersion of light . The effect of the atmosphere in this case resembles the effect of a glass prism : the path that light travels depends on its wavelength . As a result, the blue part of the spectrum from the star gives an image closer to the zenith than the red.
The effect is absent for the luminary in its zenith.
See also
- Atmospheric refraction