Overview observations of the filament. (a): 304 Å image observed from SDO/AIA. The cyan box outlines the field of view of panel b. (b): Hα images observed from NVST. The yellow and blue contours indicate the positive and negative magnetic field with levels of ±100 G. (c): observations of STEREO-A/EUVI in 195 Å. The yellow box in the bottom left corner shows the relative locations of STEREO-A, STEREO-B, and SDO at 06:50 UT. The cyan box outlines the field of view of panel d. (d): zoomed-in region of panel c. The dotted white lines in panels a and c denote the same position on the Sun. An animation available online shows the observation of NVST Hα during the period from 06:20 UT to 08:00 UT.