Interferometric Investigation of Emission Lines of the Solar Corona During the Total Solar Eclipse of 1958 October 12

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Abstract
The total solar eclipse of 1958 October 12 was observed by a Cambridge Observatories expedition on the coral atoll Atafu, in the Tokelau Islands of the South Pacific. The solar corona was photographed through a Fabry–Perot interferometer, with a 0.35 mm spacer, using narrow-band interference filters for the green ( λ 5303 A) and red ( λ 6374 A) corona lines respectively. Several good photographs were obtained, standardized photometrically and showing very good interference fringes over the whole corona, in some position angles to more than 1.8 solar radii from the Sun's centre. Immediately before and after the eclipse, interference fringes were photographed in the light of the 5461 A line from a water-cooled mercury 198 isotope lamp, to check the instrumental adjustment and to provide an instrumental fringe profile. Many line profiles and half-widths, corrected for instrumental broadening, were determined for both the corona lines and temperatures derived from them. The mean temperature from the green line was about 3.2 × 10 6 deg. K and from the red line 3.5 × 10 6 deg. K, with an error of about 10 per cent in each case.

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