Files *A.pdf are sets of all-sky maps for various latitudes. Each set is a sequence of five maps showing the sky for growing detection limits. The detection limit depends on the sky luminance, which is much larger in cities than in true nature. Star areas are proportional to their brightness. File allpdf.zip contains all of them.
The maps are computed assuming a chosen (quite common) attenuation of starlight by the atmosphere. The attenuation depends on the air transparency. The parameter of the chosen attenuation is such, that the stars are assumed to be attenuated by 0.25 mag when in zenith (so called zenith extinction). Then at 30° they are attenuated by 0.5 mag etc., depending on the amount of air between the observer and the star. With excellent transparency (zenith extinction of just 0.18 mag), starlight would be a lot stronger near horizon.
The limit given in the right bottom corner is for the faintness of the starlight as attenuated by the atmosphere, for the stars as they appear.
|allpdf.zip||2010-12-18 16:41||1.7M||indiv. latitude maps|