Light pollution at high zenith angles, as measured at Cerro Tololo Inter-American Observatory

On the basis of measurements of the V-band sky brightness obtained at Cerro Tololo Inter-American Observatory in December 2006 and December 2008 we confirm the functional form of the basic model of Garstang (1989, 1991). At high zenith angles we measure an enhancement of a factor of two over Garstang's later model when there is no marine cloud layer over La Serena/Coquimbo. No corresponding enhancement is found in the B-band.