Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Artificial Sky Luminance And The Emission Angles Of The Upward Light
  Flux   The direction of the upward light emission has different polluting effects on
the sky depending on the distance of the observation site. We studied with
detailed models for light pollution propagation the ratio $(b_{H})/(b_{L})$, at
given distances from a city, between the artificial sky luminance $b_{H}$
produced by its upward light emission between a given threshold angle
$\theta_{0}$ and the vertical and the artificial sky luminance $b_{L}$ produced
by its upward light emission between the horizontal and the threshold angle
$\theta_{0}$. Our results show that as the distance from the city increases the
effects of the emission at high angles above the horizontal decrease relative
to the effects of emission at lower angles above the horizontal. Outside some
kilometers from cities or towns the light emitted between the horizontal and
10\deg ~is as important as the light emitted at all the other angles in
producing the artificial sky luminance. Therefore the protection of a site
requires also a careful control of this emission which needs to be reduced to
at most 1/10 of the remaining emission. The emission between the horizontal and
10\deg ~is mostly produced by spill light from luminaires, so fully shielded
fixtures (e.g. flat glass luminaires or asymmetric spot-lights installed
without any tilt) are needed for this purpose.

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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con