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The vulnerable loggerhead sea turtle Caretta caretta is the most common sea turtle to nest on the beaches of the Georgia coast. A growing concern to the conservation of these long-lived marine reptiles is from non-point-source inland community lights creating shoreward sky glow that impacts turtle nesting. Calibrated quantum or radiometric light measuring devices often have limited dynamic range and resolution and are not able to effectively measure incoming irradiance, while consumer cameras images are altered to adjust for human light perception. In order to study the disorienting effect of light, low cost, portable, quickly-acquired spectral radiometric measurements of coastal light pollution are needed to fully characterize its effect on marine macrofauna, e.g., sea turtle hatchlings. Radiometric devices are expensive, have low sensitivity, low resolution, and are impractical for the large-area spatial collection of light pollution measurements in nighttime beachfront environments. Consumer cameras have large dynamic range with a variety of available mating optics, but are intended for photometric imaging of scenes in accordance with the CIE standard characterizing the human visual system. We present a recently-patented method to associate relatively low-cost CCD/CMOS RGB sensor data directly to nm-precision, visual-light irradiance spectra. Calibration uses well-characterized solar imagery at local apparent noon passing through an inexpensive apparatus comprised of multiple neutral density and narrowband filters as well as a transparent diffraction grating to simultaneously capture irradiance and spectral data for generation of calibration values. Measurements have been collected near sea turtle nesting sites in order to evaluate potential beachfront lighting experienced by the nesting female turtles and emerged hatchlings.
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