ABSTRACT
The relative apparent luminosities of the heavenly bodies can be measured even with the naked eye. Photometric quantities will be defined according to the astronomical tradition and nomenclature, which is not always the same as that used by physicists or radiometrists. On occasions, there are also refracting elements in the telescope, for example a corrector of optical aberrations made of several lenses whose transmissivities must be factored in the overall R. In particular, the English astronomer Pogson found in 1856 that the law reproduced the astronomical system of magnitudes, provided the constant k was made equal to - 2.5 and the logarithms were on the decimal base. Photographic emulsion was introduced in the astronomical field in the second half of the nineteenth century. To complete these considerations about the influence of the atmosphere on photometry of the celestial bodies, authors must add that the atmosphere contributes radiation, both by spontaneous emission and by scattering of natural and artificial lights.
