Beyond All-Sky: Assessing Ecological Light Pollution Using Multi-Spectral Full-Sphere Fisheye Lens Imaging

Abstract

Artificial light at night is a novel anthropogenic stressor. The resulting ecological light pollution affects a wide breadth of biological systems on many spatio-temporal scales, from individual organisms to communities and ecosystems. However, a widely-applicable measurement method for nocturnal light providing spatially resolved full-spectrum radiance over the full solid angle is still missing. Here, we explain the first step to fill this gap, by using a commercial digital camera with a fisheye lens to acquire vertical plane multi-spectral (RGB) images covering the full solid angle. We explain the technical and practical procedure and software to process luminance and correlated color temperature maps and derive illuminance. We discuss advantages and limitations and present data from different night-time lighting situations. The method provides a comprehensive way to characterize nocturnal light in the context of ecological light pollution. It is affordable, fast, mobile, robust, and widely-applicable by non-experts for field work.

Working with Inadequate Tools: Legislative Shortcomings in Protection against Ecological Effects of Artificial Light at Night

“…Landscapes can be brightened by skyglow to an extent which is several times higher than the natural night time brightness [327]. Nevertheless, standardized measurement methods of sky brightness to judge the impact of the skyglow from urban settings on landscapes and especially protected areas (e.g., Natura 2000) are lacking [328][329][330]. Similar to temperature and rainfall the data on the brightness of landscapes needs to be monitored and made publicly available (see also reference [331]).…”

Commentary: Brightness of the Night Sky Affects Loggerhead (Caretta caretta) Sea Turtle Hatchling Misorientation but Not Nest Site Selection

“…The most widely recommended method is digital camerabased photography (using a fisheye lens to capture the whole sky). When correctly calibrated, this method provides both qualitative (imagery) and quantitative (skyglow radiance) data (Hänel et al, 2018;Barentine, 2019;Jechow et al, 2019). While slightly more expensive, this technique can be used to examine different sectors of the sky accurately, allowing better quantification of local conditions that may be important to species responses.…”

How dark is a river? Artificial light at night in aquatic systems and the need for comprehensive night‐time light measurements

“…The camera measures the spatially resolved radiance over the whole hemisphere in three spectral bands in one image by a single measurement. The method is therefore quick, can provide many measurements per timeframe (Jechow, ; Jechow et al, ), is easily applicable during field work (Jechow et al, ; Jechow, Kolláth, Ribas, et al, ; Jechow, Kyba, & Hölker, ), and can help to extract the city emission function crucial for skyglow models (Kocifaj, Solano‐Lamphar, & Videen, ). Figure shows a false color luminance map acquired with this method at Pape Nature Reserve at the Baltic Sea (same location as Figure ).…”

“…A recent modification of the night-time all-sky architecture includes taking multiple images to get information on the light field from all directions (Jechow, Kyba, & Hölker, 2019b), which was applied in oceanography as early as 1970 with film cameras back to back for daytime operation up to 100 m depth (Smith, Austin, & Tyler, 1970). To get the full spectral radiance and directionality, a hyperspectral imaging system with a wide-angle optics, ideally dual fisheye lens geometry (Smith et al, 1970), would be required.…”