Polarization of the Sky

Horváth, Gábor; Barta, András; Hegedüs, Ramón

doi:10.1007/978-3-642-54718-8_18

Cited by 29 publications

(22 citation statements)

References 103 publications

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“…We found that gibbous moon skylight (93–98% fullness; Fig. 2 A–B) measured in rural South Africa reached degrees of polarization as high as 0.6–0.7, similar to values reported for sunlit skies (Berry et al ., 2004; Horváth et al ., 2014) but much greater than the levels, around 0.27, for lunar skylight measured in Europe (Supplement S2.1 A; 80% illuminated). We also found that the maximum degree of polarization for other lunar phases was lower, with degree of polarization corresponding to moon fullness (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…On all moonlit nights the highest degree of polarization was measured in a band at approximately 90° from the moon (Fig. 2), mimicking that of the sunlit sky (Berry et al ., 2004; Horváth et al ., 2014), as found for previous studies of the polarization of lunar skylight (Gál et al ., 2001; Kyba et al ., 2011; Barta et al ., 2014; Tang et al ., 2016). Although the serial-imaging protocol we employed can lead to the accumulation of motion artefacts, particularly during long exposures, these effects appeared to be limited, for the most part, to a small number of bright stars (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…It has been suggested that the field cricket Gryllus campestris has adapted a low threshold (degree of linear polarization = 0.05) that permits the detection of the weakly polarized skylight often observed in its natural environment (Labhart, 1996, 1999). An assessment of the daytime skylight cues available near the crickets’ collection site, using an artificial polarization-sensitive “neuron”, suggested that degrees of polarization are typically quite low, as a result of haze and cloud cover, with median values of 0.13 and 0.23 in the solar and antisolar halves of the sky respectively (Labhart, 1999); as compared with values in excess of 0.60 measured in clear skies (Horváth et al ., 2014). While the low intensity of lunar skylight presents a challenge for the detection of polarized skylight at night, the superposition eyes of E. satyrus are well adapted to detect lunar skylight cues, and they orient well even under very dim conditions (Dacke et al ., 2011; Smolka et al ., 2016).…”

Section: Introductionmentioning

confidence: 99%

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Orienting to Polarized Light at Night—Matching Lunar Skylight to Performance in a Nocturnal Beetle

Foster

Kirwan

Jundi

et al. 2018

Preprint

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A degree-of-polarization threshold for orientation behaviour is 15 reported for nocturnal dung beetle Escarabaeus satyrus in the context 16 of measurements showing changes in the degree of polarization of 17 skylight with lunar phase. 18 Abstract 19For polarized light to inform behaviour, the typical range of degrees of 20 polarization observable in the animal's natural environment must be 21 above the threshold for detection and interpretation. Here we present 22 the first investigation of the degree of linear polarization threshold for 23 orientation behaviour in a nocturnal species, with specific reference to 24 the range of degrees of polarization measured in the night sky. An 25 effect of lunar phase on the degree of polarization of skylight was 26 found, with smaller illuminated fractions of the moon's surface 27 corresponding to lower degrees of polarization in the night sky. We 28 found that South African dung beetle Escarabaeus satyrus 29 (Boheman, 1860) can orient to polarized light for a range of 30 degrees of polarization similar to that observed in diurnal insects, 31 reaching a lower threshold between 0.04 and 0.32, possibly as low as 32 2 0.11. For degrees of polarization lower than 0.23, as measured on a 33 crescent moon night, orientation performance was considerably 34 weaker than that observed for completely linearly-polarized stimuli, 35 but was nonetheless stronger than in the absence of polarized light. 36

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Orienting to Polarized Light at Night—Matching Lunar Skylight to Performance in a Nocturnal Beetle

Foster

Kirwan

Jundi

et al. 2018

Preprint

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“…The celestial distribution of the angle of the skylight polarization, being the same under all possible sky conditions (clear, fog, clouds, etc), is used for the orientation by polarization-sensitive animals, including many vertebrates [3](Horváth et al, 2014). There is considerable behavioral and physiological evidence for polarization-based navigation in vertebrates, including fish, reptiles and birds, but not in mammals, while it is known that mammals, including humans, can still perceive the polarization of light to some extent (Muheim, 2011; Wehner, 2014) [4,5].…”

Section: Introductionmentioning

confidence: 99%

Model of polarization selectivity of the intermediate filament optical channels

Khmelinskii¹,

Zueva²,

Inyushin³

et al. 2015

Photonics and Nanostructures - Fundamentals and Applications

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Recently we have analyzed light transmission and spectral selectivity by optical channels in Müller cells and other transparent cells, proposing a model of their structure, formed by specialized intermediate filaments [1,2]. Our model represents each optical channel by an axially symmetric tube with conductive walls. Presently, we analyze the planar polarization selectivity in long nanostructures, using the previously developed approach extended to structures of the elliptic cross-section. We find that the output light polarization angle depends on the a/b ratio, with a and b the semiaxes of the ellipse. Experimental tests used a Cr nano-strip device to evaluate the transmitted light polarization. The model adapted to the experimental geometry provided an accurate fit of the experimental results.

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“…around sunset and sunrise when large portions of the sky are red and orange, or when the sky is covered by grey or white clouds or fog. However, in the latter cases the d of skylight can be so low [8–11] that it falls below the perception threshold d * of Haidinger's brushes. The brushes have the best contrast when d approaches 100%, for instance looking at a white area on a liquid crystal computer monitor, which employs a linear polarizer as part of the image-forming technology [2,12].…”

Section: Introductionmentioning

confidence: 99%

Celestial polarization patterns sufficient for Viking navigation with the naked eye: detectability of Haidinger's brushes on the sky versus meteorological conditions

et al. 2017

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If a human looks at the clear blue sky from which light with high enough degree of polarization d originates, an 8-shaped bowtie-like figure, the yellow Haidinger's brush can be perceived, the long axis of which points towards the sun. A band of high d arcs across the sky at 90° from the sun. A person can pick two points on that band, observe the yellow brushes and triangulate the position of the sun based on the orientation of the two observed brushes. This method has been suggested to have been used on the open sea by Viking navigators to determine the position of the invisible sun occluded by cloud or fog. Furthermore, Haidinger's brushes can also be used to locate the sun when it is below the horizon or occluded by objects on the horizon. To determine the position of the sun using the celestial polarization pattern, the d of the portion of the sky used must be greater than the viewer's degree of polarization threshold d* for perception of Haidinger's brushes. We studied under which sky conditions the prerequisite d > d* is satisfied. Using full-sky imaging polarimetry, we measured the d-pattern of skylight in the blue (450 nm) spectral range for 1296 different meteorological conditions with different solar elevation angles θ and per cent cloud cover ρ. From the measured d-patterns of a given sky we determined the proportion P of the sky for which d > d*. We obtained that P is the largest at low solar elevations θ ≈ 0° and under totally or nearly clear skies with cloud coverage ρ = 0%, when the sun's position is already easily determined. If the sun is below the horizon (−5° ≤ θ < 0°) during twilight, P = 76.17 ± 4.18% for dtruemin∗=23normal% under clear sky conditions. Consequently, the sky-polarimetric Viking navigation based on Haidinger's brushes is most useful after sunset and prior to sunrise, when the sun is not visible and large sky regions are bright, clear and polarized enough for perception of Haidinger's brushes.

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Polarization of the Sky

Cited by 29 publications

References 103 publications

Orienting to Polarized Light at Night—Matching Lunar Skylight to Performance in a Nocturnal Beetle

Orienting to Polarized Light at Night—Matching Lunar Skylight to Performance in a Nocturnal Beetle

Model of polarization selectivity of the intermediate filament optical channels

Celestial polarization patterns sufficient for Viking navigation with the naked eye: detectability of Haidinger's brushes on the sky versus meteorological conditions

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