The number of phase bins. The maximum number of phase bins for ordinary sampling is given by the minimum period divided by the time bin size. e.g. if the data is binned in 1 second bins and the minimum period is 4 seconds then the maximum number of phase bins for standard sampling is 4. It is valid to oversample datasets, i.e. set NPHASE to greater than this maximum, if the dataset is long and contains many counts. However, oversampling may well produce spurious peaks in the periodogram at integer multiples of the bin width.