In 1975, Deeming1 demonstrated that it is possible to use the Discrete Fourier transform (DFT) for the Fourier and power spectrum analysis of unequally-spaced data, with results that are comparable to analysis with equally-spaced data. 

Peranso implements the algorithm presented by Deeming in the afore mentioned publication. 

The DFT dialog box is similar to the Lomb-Scargle dialog box. Prominent periods of the Period Window appear as peaks.

(1) Deeming, T.J., 1975, Ap&SS, 36, 137