Running difference images of Encke and ISON from STEREO-A/HI-2 (left panel) and HI-1 (middle panel). Orbits of comets Encke (yellow line) and ISON (red line) in the Heliocentric-Aries-Ecliptic (HAE) coordinate system (right panel). Dashed lines indicate where the trajectory is below the ecliptic plane. The Earth is represented by the green dot (with the associated orbit dashed line style), while STEREO-A and B are shown with the red and blue dots, respectively. For reference, the position of the inner planets is also shown. The corresponding animations for each panel are available online.