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We report the results of polarimetric observations of the total solar eclipse of 21 August 2017 from Rexburg, Idaho (USA).We use three synchronized DSLR cameras with polarization filters oriented at 0, 60, and 120 to provide high-dynamic-range RGB polarization images of the corona and surrounding sky.We measure tangential coronal polarization and vertical sky polarization, both as expected. These observations provide detailed detections of polarization neutral points above and below the eclipsed Sun where the coronal polarization is canceled by the sky polarization.We name these special polarization neutral points afterMinnaert and Van de Hulst. 

Few colorimetric analyses of natural rainbows (i.e., bows seen in rain showers) have been published, and these are limited either to approximate techniques (colorimetrically calibrated red–green–blue (RGB) cameras) or to rainbow proxies (bows seen in sunlit water-drop sprays). Furthermore, no research papers provide angularly detailed spectra of natural rainbows in the visible and near-IR. Thus some uncertainty exists about whether the published spectra and colors differ perceptibly from those in natural rainbows. However, battery-powered imaging spectrometers now make possible direct field measurements of the observed chromaticities and spectra in such bows. These data (1) show consistent spectral and colorimetric patterns along rainbow radii and (2) let one subtract additively mixed background light to reveal the intrinsic colors and spectra produced by rainbow scattering in nature. 

All-sky polarization images were measured from sunrise to sunset and during a cloud-free totality on 21 August 2017 in Rexburg, Idaho using two digital three-camera all-sky polarimeters and a time-sequential liquid-crystal-based all-sky polarimeter. Twenty-five polarimetric images were recorded during totality, revealing a highly dynamic evolution of the distribution of skylight polarization, with the degree of linear polarization becoming nearly zenith-symmetric by the end of totality. The surrounding environment was characterized with an infrared cloud imager that confirmed the complete absence of clouds during totality, an AERONET solar radiometer that measured aerosol properties, a portable weather station, and a hand-held spectrometer with satellite images that measured surface reflectance at and near the observation site. These observations confirm that previously observed totality patterns are general and not unique to those specific eclipses. The high temporal image resolution revealed a transition of a neutral point from the zenith in totality to the normal Babinet point just above the Sun after third contact, providing the first indication that the transition between totality and normal daytime polarization patterns occurs over of a time period of approximately 13 s.