a) Autocorrelation of the optical pulsar flux obtained by piecewise superimposing the envelope of the histogram of Fig. 5; b) detected optical flux versus time, as obtained by folding all the periods of the observing run and taking the average. The detected photon time series were identical for a) and b), and the pulsar period T was divided into 112 bins in both cases. Clearly, method a) provided the better signal-to-noise ratio. (TOA ... time of arrival of photons).