Pollution in the Visible
Visually, the La Silla sky in direction of La Serena and Vallenar displays a faint, but clearly visible glow. In order to quantify this pollution, we used the SuSI-2 imager to measure the sky background toward various azimuths.
In order to quantify that effect, and to measure the variations as a function of the Altitude, we performed a series of measurements with Alt in the 15-85o range in various directions: toward La Serena, toward Vallenar, and toward the Andes. The resulting magnitudes are plotted in Figure 3.
Except in the U-band, the effect of La Serena is only marginally detectable for Altitudes lower than 20deg. In U, it will be necessary to confirm these measurements spectroscopically.