Two examples of TEC-screen fits from the observation shown in Fig. 3. Values are in differential TECU withrespect to station CS 002. Each circle represents a LOFAR station; colour coded within the circle is the dTEC value for that station (we note that the markers are filled with the colour corresponding to the measured dTEC). The background colour is the TEC screen fitted across the array as described in the text. Stations crossed with an X are the same excluded from Fig. 2. The full movie is available in the online material.