The brightness and the spectral distribution of the zenith sky in the 5300–6600 Å region were measured during the eclipse of 12 November 1966 at Quehua, Bolivia. At totality, the brightness at 5600 Å was observed to be 8.4 kR/Å, three orders of magnitude lower than the 2.2 × 104 kR/Å for the normal day sky. The spectral distribution is presented here in terms of a single parameter, the effective blackbody temperature for determining the predominance of secondary scattering during midtotality. The effective temperature was observed to change from 9100 °K for normal day sky to 11,100°K during totality.
B. S. Dandekar, "Measurements of the Zenith Sky Brightness and Color During the Total Solar Eclipse of 12 November 1966 at Quehua, Bolivia," Appl. Opt. 7, 705-710 (1968)