Downwelling spectral irradiance during evening twilight as a function of the lunar phase

We measured downwelling spectral vector irradiance (from 350 to 800 nm) during evening civil and nautical twilight (solar elevation down to -12°). Nine sets of measurements were taken to cover the first half of the lunar cycle (from the new to full moon) and were also used to calculate chromaticity...

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Bibliographic Details
Published in:Applied optics (2004) 2015-02, Vol.54 (4), p.B85-B92
Main Authors: Palmer, Glenn, Johnsen, Sönke
Format: Article
Language:English
Subjects:
Animals
Anthozoa
Brightness
Ecology
Elevation
Evening
Irradiance
Light
Lighting
Lizards
Lunar phases
Mathematical analysis
Moon
Moths
Motion
North Carolina
Optical Phenomena
Predatory Behavior
Reproduction
Spectra
Stratospheric Ozone
Sunlight
Twilight
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Summary:We measured downwelling spectral vector irradiance (from 350 to 800 nm) during evening civil and nautical twilight (solar elevation down to -12°). Nine sets of measurements were taken to cover the first half of the lunar cycle (from the new to full moon) and were also used to calculate chromaticity (CIE 1976 u'v'). The lunar phase had no consistent effect on downwelling irradiance until solar elevation was less than -8°. For lower solar elevations, the effect of the moon increased with the fraction of the illuminated lunar disk until the fraction was approximately 50%. For fractions greater than 50%, the brightness and chromaticity of the downwelling irradiance were approximately independent of the fraction illuminated, likely because the greater brightness of a fuller moon was offset by its lower elevation during twilight. Given the importance of crepuscular periods to animal activity, including predation, reproductive cycles, and color vision in dim light, these results may have significant implications for animal ecology.
ISSN:1559-128X
2155-3165
DOI:10.1364/AO.54.000B85