set term png set size 1.8 set grid set out '28-30.png' S = (17-1)*3600 + (51+2.8)*60 + 47 t(x) = S + x B=(24-6)*3600 E=(24+6)*3600 set xdata time set format x "%H:%M" set title \ 'log10 ( voltage at PV panel / 0.1 mV ) on 28-30 June 2006, Kravi hora, Brno' set xlabel 'Local solar time, being 56.5 min less then CEST' plot '28-1.txt' using ($1 + S):(log10($2)+4) ,\ 'casy2.tab' using ($1):($2+1) with impulses title \ 'Sunset and Sun at -6, -12, -15 degrees and vice versa'