The spectral power distribution of sky glow allows for the identification of stray outdoor light types and their relative contribution to light pollution. Night Sky Metrics offers measurements calibrated in absolute spectral radiance units, allowing for the calculation of sky brightness in a variety of photometric systems by synthetic photometry. Important indicators of environmental impact may also be obtained such as scotopic/photopic or melanopic/photopic ratios. Single value metrics of sky glow color such as CCT or astronomical B minus V are accurately calculated.
One example utilizes the device to measure the effect of atmospheric extinction on the spectrum of sky glow from a major city. A series of observations at a point distant from the city from horizon to zenith at a constant azimuth reveal the changes in spectral content, and the relative contribution of the natural airglow as the observations approach the zenith.
Another example demonstrates the relative contribution from different light sources within a city where lighting retrofits from HPS to LED are being performed. Zenith skyglow measurements are used in a large metropolitan area.
A third example is the collection of baseline data, both from within and at a distance from a city. The character of artificial skyglow is quantified using both all-sky broadband photometry and spectroscopy of selected points in the sky. With repeat measurements, the effect of altering outdoor lighting practices or changing atmospheric conditions upon the environment may be determined. In the example below, the Sky Quality Camera equipment and software by Euromix was used for the all sky brightness and CCT measurements.
