Night Sky Brightness Measurements
Updated 06/26/07 by EEF
- 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:
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
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