Evolution of the 6 October 2010 CME observed in COR2, HI1 and HI2 images from STEREO-A (left column) and STEREO-B (right column). Contours of elongation angle (green) and position angle (blue) are overplotted. The vertical red line in the COR2 images marks the 0° position angle contour. The horizontal lines (red) on all panels indicate the position angle of Earth. The features (F1 and F2) tracked in coronagraph fields of view and the features (Feature 1 and Feature 2) tracked in the HI field of view are shown with arrows (black) in the top and middle panels, respectively.