Systems for imaging optical emissions all have a detection sensitivity which, be it uniform or not, can make image interpretation very difficult. A time differential technique involving pixel by pixel subtraction of successive images has been developed to overcome this problem. The technique has been applied to images of pulsating aurorae recorded with a low-light-level television system. Individual auroral forms exhibit within a short interval of time a diversity of pulsation modes not evident by direct visual inspection of the television images. The results are important for possible source mechanisms or any meaningful classification scheme for pulsating aurorae. ¿ American Geophysical Union 1992