Visual description of the process of period determination for two different cases: a standard situation (analysis of IOMC 0460000022) on the left and an example of aliasing (IOMC 5228000021) on the right. In both cases, the plots are: top: the light curve without folding. For the light curve affected by aliasing the large temporal gap can be appreciated. Middle: periodogram from 0 to 10 days. The peaks are much narrower in the standard case. In the aliasing example, the smoothed periodogram taking into account the aliasing effect (see text) is overplotted in green. Bottom: detail of the method used to determine the uncertainty of the period. In red, the continuum plus gaussian fit to the peak is plotted.