Fig. 1. (A) Experimental arrangement of the 180° field-of-view imaging polarimetric measurement of the reflection-polarizational characteristics of horizontal water-dummies. (B) Relative reflectivities of the matt black and matt grey cloths (used as substrata of the glass panes) as well as the black and grey water-dummies. (C) The mirror image of the apparent celestial path of the sun during the measurements on 18 July 2002 under clear, cloudless skies at the Hungarian Kunfehértó (46°23' N, 19°24' E) in a system of polar coordinates, where the solar azimuth angle (_s) is measured clockwise from the magnetic north, and the solar elevation (_s) is measured radially from the horizon. Dots show the solar positions when the measurements were performed. Black dots represent the solar positions when the patterns in Figs 2 and 3 were measured.