- Rapid capturing the night sky in a high resolution mosaic
- Precise measurement of sky brightness and glare across the entire celestial hemisphere
- Identification of light pollution sources, and
- Separation of natural and human-caused sky brightness.
Sites are selected that have a good view of the horizon with minimal obstructions. Small parks generally have one representative data site, whereas large parks may have several. Data are collected for 1–8 hours per night, and often on multiple nights. Weather conditions constrain data collection, as it has to be at least 95 percent clear to capture sky brightness conditions properly. Only nights with no moon are suitable. In addition to the photometric measures, field technicians make observations of the nighttime environment and sky quality. This enables the NPS to identify relationships between numerical data and visual features of the night and better understand human visual perception of the natural lightscape.
The NPS methods for night sky measurement provide park managers with scientifically sound information from which to understand the quality of their natural lightscape and the threats to it. The core of our methods have been peer-reviewed and published (Duriscoe, 2007). Additional technical advancements are currently being tested and will receive the same level of scrutiny. To date, nearly 100 NPS sites have been surveyed. This represents a substantial baseline inventory of conditions at parks across the United States. The NPS is also working toward synthesizing this data into simplified products to better inform park managers and the public.
Future extensions of the methodology may include development of a long-term monitoring program and measuring the sky in different spectra (colors) to provide a better understanding of ecological impact.
Duriscoe D., Luginbuhl C., and Moore C. 2007. Measuring Night Sky Brightness with a Wide-Field CCD Camera. Publications of the Astronomical Society of the Pacific, Vol 119.