The high-resolution light-polluted night-sky spectrum at Mount Hamilton, California

Sky spectra were recorded over San Jose at the Lick Observatory over the 3800-9200 Angstrom spectral range, with a spectral resolution of 45,000. Strong atomic lines were detected from Al I, Ar I, Hg I, K I, Li I, Na I, Ne I, Sc I, Sc II, Th I, Th II, and from O I and OH nightglow features. Spectra are contrasted for observations over San Jose ( west), the zenith direction, and the eastern sky. When observing in the easterly direction, the emission intensity is still 20%-30% of that seen toward the west. For a natural and stable terrestrial nightglow line, O I lambda5577, the intensity is comparable in either direction. A variety of line shapes are observed, reflecting the outputs of the melange of pollution sources. A total of 177 identified light-pollution lines were observed, of which more than half are due to Sc I and Sc II. The Sc I lines show a systematic shift to longer wavelengths from the expected positions, amounting to an average of 25 mAngstrom. This is presumably a consequence of their origin, high-pressure metal halide lamps. By comparing the intensity of the strongest pollution lines and continuum (from Na) with the nightglow O I lambda5577 line, a figure of merit for the pollution line intensity is the equivalent of 4 kR for the atmospheric conditions and viewing geometry investigated.