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Kelber, A., Balkenius, A., & Warrant, E. J. (2002). Scotopic colour vision in nocturnal hawkmoths. Nature, 419(6910), 922–925.
Abstract: Humans are colour-blind at night, and it has been assumed that this is true of all animals. But colour vision is as useful for discriminating objects at night as it is during the day. Here we show, through behavioural experiments, that the nocturnal hawkmoth Deilephila elpenor uses colour vision to discriminate coloured stimuli at intensities corresponding to dim starlight (0.0001 cd x m(-2)). It can do this even if the illumination colour changes, thereby showing colour constancy-a property of true colour vision systems. In identical conditions humans are completely colour-blind. Our calculations show that the possession of three photoreceptor classes reduces the absolute sensitivity of the eye, which indicates that colour vision has a high ecological relevance in nocturnal moths. In addition, the photoreceptors of a single ommatidium absorb too few photons for reliable discrimination, indicating that spatial and/or temporal summation must occur for colour vision to be possible. Taken together, our results show that colour vision occurs at nocturnal intensities in a biologically relevant context.
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Schnitt, S., Ruhtz, T., Fischer, J., Hölker, F., & Kyba, C. C. M. (2013). Temperature stability of the sky quality meter. Sensors (Basel), 13(9), 12166–12174.
Abstract: The stability of radiance measurements taken by the Sky Quality Meter (SQM)was tested under rapidly changing temperature conditions during exposure to a stable light field in the laboratory. The reported radiance was found to be negatively correlated with temperature, but remained within 7% of the initial reported radiance over a temperature range of -15 degrees C to 35 degrees C, and during temperature changes of -33 degrees C/h and +70 degrees C/h.This is smaller than the manufacturer's quoted unit-to-unit systematic uncertainty of 10%,indicating that the temperature compensation of the SQM is adequate under expected outdoor operating conditions.
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