Comparison of flux density light curves for the secondary calibrator PKS 1830–3602 in the image and visibility domains. We used imfit on images generated in 1 min bins to obtain the green curve, which represents the image-domain flux densities with associated errors. The red curve shows flux densities derived using uvmodelfit in the visibility domain. The error bars represent the 1σ statistical uncertainty. We observe consistent trends between the two methods, validating the robustness of our approach. Differences in error magnitudes reflect the distinct modelling assumptions in each domain. Image-domain errors are larger due to contributions from deconvolution and beam uncertainties, while visibility-domain errors remain smaller because they arise from direct model fitting in the Fourier domain.