An analysis of the CLEAN algorithm of Fourier-analysis of short time series and time series consisted for short segments separated by long irregular gaps is made. It is supposed that analysed time series consist of harmonic components with amplitude $A$ and a period larger than the longest segment of the time series and the noise component with variance $N^2$. We construct the reliability maps determing the regions of parameters ($\nu,\varphi$), where $\nu$ is a frequency and $\varphi$ is a phase of the harmonic component where method CLEAN can determine the values $\nu$ and $\varphi$ with the fixed accuracy.The results of our analysis are used for searАhing the harmonic components in the H$_{\beta}$ line profile variations in the spectra of the triple star $\delta\,$Ori~A obtained in 2004 with 6-m telescope of the Special Astrophisical Observatory of the Russian Academy os Sciences.