The variability in γ-ray flux observed during total solar eclipses holds significant scientific interest. For our study, we employed two large-volume sodium iodide detectors to measure the γ-ray flux before, during, and after the "eclipse of the century" on 22 July 2009, visible from India. Analyzing the acquired spectra proved challenging due to the fluctuating levels of radon daughters. Furthermore, the presence of rain during the eclipse added further complexity to the analysis. To address these issues, we developed a RooFit-based method. Our newly devised model combines two exponential functions with 12 Gaussian functions representing the dominant γ-ray lines, enabling the generation of a comprehensive compound energy spectrum. We successfully demonstrated the effectiveness of this model in fitting individual spectra of various time durations, irrespective of rain or time, and its potential to isolate the influence of rain. Upon re-evaluating the Siliguri data, we observed a notable reduction in the variability of γ-ray flux. ROOFit was used successfully for the first time to the background γ-ray spectrum without considering detector parameters.