Determination of atmospheric refraction from the distortion of the Sun's disc
Abstract
The solar disk distorted by atmospheric refraction is used to determine the first derivative of the refraction with respect to the true zenith distance of the center of the Sun's disk at low altitudes and compared with those obtained from Bennett's formula taken from the Almanac for Computers (1991) and from the table of Radau (1889). At low altitude, there was a large scatter in the deviation of the measured derivatives from those obtained from Bennett's formula or from Radau's table, but contrary to Kort (1960), only a small mean deviation was found. An attempt to determine the second derivative of the refraction with respect to the true zenith distance was not successful because of irregular diffraction. The refraction was recomputed after fitting one of the parameters of Bennett's formula so that its first derivative and the measured one should be equal. In this case also, only a small mean deviation of the fitted refractions from those determined by Bennett's formula was obtained.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 November 1993
 Bibcode:
 1993A&A...278..659G
 Keywords:

 Astrometry;
 Atmospheric Refraction;
 Solar Limb;
 Sun;
 Distance;
 Refractivity;
 Spectroheliographs;
 Zenith;
 Solar Physics