Average V-band magnitude of V7 for each observing night, showing some long-term variability of an undetermined nature. The V-band data is plotted in black, while the I-band data is plotted in red, with a fixed offset to bring the two data sets onto the same plot. The variations in (V − I) therefore appear to indicate a change with time in the colour of V7, although the I-band data is poor. The x-axis is given in HJD-2 450 000.