We investigate the magnification due to refraction of the apparent horizontal sizes of finite celestial bodies, such as the Sun or Moon. Two models are discussed and compared with the earlier works of Biot and Chauvenet. It is shown that the apparent horizontal size of the object varies with respect to its true horizontal size as a function of altitude or zenith distance, from a reduction of about 0.0276percent at the zenith, to an amplification of about 0.0045percent when the object appears just at the horizon (namely, when the true altitude gamma is negative and related to the corresponding refraction R by gamma velence -R). It is also shown that the apparent horizontal size is equal to the true size when the true altitude gamma is related to the corresponding refraction R by gamma velence -R/2. Thus, the total magnification (and reduction) range for differently sized objects is about 0.032percent-0.033percent and depends on the refraction.
展开▼
