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

Journal Article (Journal Article)

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.

Full Text

Duke Authors

Cited Authors

  • Palmer, G; Johnsen, S

Published Date

  • February 2015

Published In

Volume / Issue

  • 54 / 4

Start / End Page

  • B85 - B92

PubMed ID

  • 25967843

Electronic International Standard Serial Number (EISSN)

  • 1539-4522

International Standard Serial Number (ISSN)

  • 1559-128X

Digital Object Identifier (DOI)

  • 10.1364/ao.54.000b85


  • eng