Left: CLEAN image for a time interval from 02:08 to 02:10 UT at 13–16 keV with a CLEAN 60–80 keV 50% contour (black). Vis_FwdFit contours at 50% of the maximum and coronal source positions (coloured dots) are displayed for three energy ranges (10–11 keV (pink), 13–16 keV (green) and 20–25 keV (blue)) showing the increasing altitude of the coronal source location with energy. Right: the peak radial position R plotted against X-ray energy ϵ, for both the CLEAN (red) and Vis_FwdFit (blue) algorithms. The gradient α = dR/ dϵ ± error found from each linear fit is shown (grey dashed lines) on the graph.