Abstract
Values of the relative luminance of the various areas of Mars derived from over 3500 visual estimates in white, green, and red light made near the favorable oppositions of 1941 and 1958 are combined to produce a low-resolution (∼10°), smoothed photometric map of Mars near perihelion. Tables V to VII give the mean relative luminance β as a function of areographic longitude λ at 9° intervals and latitude β at 7° intervals for the equatorial and polar regions, the latter at different seasons. Instrumental and atmospheric effects on the apparent contrast of the dark areas, in particular Syrtis Major, are discussed and the true reflectivity of the darkest regions is estimated (A ν ⋍ 0.04) . Calculations of the effects of finite resolution in visual, photographic, and photoelectric observations are presented for a photometric model of Syrtis Major.
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