The Bloomfield1 method is quite similar to the Lomb-Scargle method, and also calculates a power spectrum, starting from unequally-spaced data, using the Least Squares Standard Technique. 


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


(1) Bloomfield, P., 1976, Fourier Analysis of Time Series: An Introduction, Wiley, New York.