Night Sky Brightness Measurements

• BROAD BAND MEASUREMENTS
• SPECTRAL MEASUREMENTS

• SATELLITE MEASUREMENTS (see Cinzano et al. 2001, MNRAS 328, 689 PDF)

• Martin Aubé (Département de Physique, Université de Sherbrooke, Canada) took sky spectra from the summit of Mt. Hopkins the nights of 28 and 29 May 2006. The plots below show his results. He used a spectrograph built to measure calibrated sky spectra and thus monitor sky brightness as a function of wavelength: SAND-2. Several spectral lines of interest are indicated. Only the oxygen lines are natural. Note in particular "Na HP" which is a band of lines generated by high-pressure sodium lamps. The spectra were acquired at 3 elevations each, as marked, and at azimuths toward Tucson (roughly North) and Nogales (roughly South). The plots have identical scales.
  
  Note that at elevation 15 degrees, the sky dome over Tucson is much brighter than that over Nogales. But by elevation 30 degrees, the brightnesses of the two domes are similar. The population in the Tucson area (about 64 km away) is about 3 times that in Nogales (predominantly in Sonora, Mexico, about 50 km away). However, light codes in the Tucson area impose cutoffs in lamps to minimize uplight, which may explain the rapid fall-off of the Tucson dome brightness. The continuum over Nogales at elevation 30 degrees was raised by the Milky Way during that particular observation.

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