  The STEREO mission has been providing stereoscopic view of filament eruptions
in EUV. The clearest view during a filament eruption is seen in He II 304 A
observations. One of the main problems visualizing filament dynamics in He II
304 A is the strong background contrast due to surface features. We present a
technique that removes background features and leaves behind only the
filamentary structure, as seen by STEREO-A and B. The technique uses a pair of
STEREO He II 304 A images observed simultaneously. The STEREO-B image is
geometrically transformed to STEREO-A view so that the background images appear
similar. Filaments being elevated structures, i.e., not lying on the same
spherical surface as background features, do not appear similar in the
transformed view. Thus, subtracting the two images cancels the background but
leaves behind the filament structure. We apply this technique to study the
dynamics of the filament eruption event of 22 May 2008, which was observed by
STEREO and followed by several ground-based observatories participating in the
Joint Observing Programme (JOP 178).
