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Kocifaj, M., Solano Lamphar, H. A., & Kundracik, F. (2015). Retrieval of Garstang's emission function from all-sky camera images. Mon. Not. R. Astron. Soc., 453(1), 819–827.
Abstract: The emission function from ground-based light sources predetermines the skyglow features to a large extent, while most mathematical models that are used to predict the night sky brightness require the information on this function. The radiant intensity distribution on a clear sky is experimentally determined as a function of zenith angle using the theoretical approach published only recently in MNRAS, 439, 3405â3413. We have made the experiments in two localities in Slovakia and Mexico by means of two digital single lens reflex professional cameras operating with different lenses that limit the system's field-of-view to either 180Âº or 167Âº. The purpose of using two cameras was to identify variances between two different apertures. Images are taken at different distances from an artificial light source (a city) with intention to determine the ratio of zenith radiance relative to horizontal irradiance. Subsequently, the information on the fraction of the light radiated directly into the upward hemisphere (F) is extracted. The results show that inexpensive devices can properly identify the upward emissions with adequate reliability as long as the clear sky radiance distribution is dominated by a largest ground-based light source. Highly unstable turbidity conditions can also make the parameter F difficult to find or even impossible to retrieve. The measurements at low elevation angles should be avoided due to a potentially parasitic effect of direct light emissions from luminaires surrounding the measuring site.
MÃ¼ller, A., Wuchterl, G., & Sarazin, M. (2011). Measuring the Night Sky Brightness with the Lightmeter. ReVMexAA, 41, 46â49.
Abstract: We present a newly developed, low-cost photometer for long-term monitoring of the night sky brightness and
light pollution on Earth. The so-called Lightmeter is an as far as possible stand-alone operational, fully
weatherproof, and maintenance-free device. It provides a high data sampling rate of up to 1 Hz as well as a
superb sensitivity covering the whole brightness range down to the darkest night time conditions. The excellent
performance of the Lightmeter allows a continuously monitoring of the night sky brightness and opens a wide
range of applications at an observatory site like determining overall sky conditions in real time, cloud detection
and estimation of their velocity, measuring relative changes in extinction as well as the detection of long term
trends in brightness caused by an increase of artificial illumination. We will present first results of measurements
taken at Cerro Armazones, one of the best obser