Abstract
Abstract We report on early results from a suite of instruments for imaging and spectra we deployed to Salem, Oregon, for two minutes of totality at the August 21, 2017, total solar eclipse. Our instruments included refracting telescopes and telephoto lenses for use with CCD detectors and DSLR cameras, narrow-band filters at the wavelengths of coronal emission lines ([Fe XIV] 530.3 nm and [Fe X] 637.4 nm), and spectrographs. We also monitored the effect of the eclipse penumbra and umbra on the terrestrial atmosphere.
Highlights
The total solar eclipse of August 21, 2017, was the first whose totality crossed only United States territory since the origin of the country, and the first to cross the Continental United States from coast to coast in 99 years
The relationship of the individual white-light coronal structures to the distribution of magnetic fields observed on the surface of the Sun is sometimes quite problematic, as observed from the coronagraphs on the Solar and Heliospheric Observatory (SOHO) and the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI; Howard et al, 2008) suite of instruments on NASA’s Solar TErrestrial RElations Observatory (STEREO)
We have been monitoring the ratio of these spectral lines over the last solar-activity cycle, showing that the lower-ionization line, typical of a coronal temperature of 1 MK or less, is stronger than the higher-ionization line, typical of a coronal temperature of ∼1.5 MK at solar minimum, as we found here
Summary
The total solar eclipse of August 21, 2017, was the first whose totality crossed only United States territory since the origin of the country, and the first to cross the Continental United States from coast to coast in 99 years. Our observations follow earlier high-resolution imaging in streamers (Pasachoff et al, 2007, 2009) and in polar plumes (Pasachoff et al, 2008). (The instrument suite was named after Fr. Angelo Secchi, director of the Vatican Observatory in the 19th century, whose 200th birth anniversary was celebrated with a symposium in Rome; Pasachoff, 2018b.) One of the ways to do this is to observe the white-light corona during total solar eclipses at high spatial resolution with subsequent computer data processing, e.g., Koutchmy et al (1988), Druckmüller et al (2006). High-quality pictures of the white-light corona during the eclipse and their processing with a computer allows us to distinguish small-scale coronal structures, for example, around 5 arc seconds or less, whose contrast between them is very low, and which are lost with standard exposures. An array of photo-sensors was used to measure the sky brightness
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