Preliminary results on the Extinction and Night Sky Background in UBV on   La Silla and ALMA site
  We report on measurements of the extinction in the U, B & V bands and of the NSB (Night Sky Background) during 2 dark periods on La Silla Observatory and at 4000-5000m on the ALMA site using an UV optimized 25 cm portable telescope. 
E. Giraud, G.Vasileiadis, P. Valvin, I. Toledo