Distribution of linear polarization degree (a) and polarization vectors (b) over the comet C/2014 A4 (SONEAR) coma derived through the R filter. The polarization (in percent) is color-coded (see scale bar above the left-hand image). The location of the optocenter is indicated with a white cross. The orientation of the vectors gives the direction of the local polarization plane, and the length of the vectors the degree of polarization. The projected directions toward the Sun, north, east, and comet velocity vector (V) are indicated.