A dopplergraph of the solar corona taken with the LASCO
C1 coronagraph which employed a tunable Fabry–Pérot interferometer
to recover scans of the solar corona at a number of wavelengths near the FeXIV green line at 5308 Å. The picture is a color-coded image of the doppler shift of the line, which may be associated with the coronal plasma velocity towards or away from the satellite camera. In calculating the velocity, the velocity due to solar rotation has been subtracted.
The word dopplergraph is a combination of the words doppler and photograph . Just as a photograph is a two-dimensional record of variations in light intensity, a dopplergraph is a two dimensional record of variations in the doppler shift in light intensity. In fact, a dopplergraph need not be a record of the shift of visible light, but of any radiated wave, which includes electromagetic waves and acoustic waves. Since the doppler shift is caused by the velocity of the radiating source towards or away from the viewer, a dopplergraph is a picture of the velocities associated with the sources being viewed.