Absolute value of the radial mean of the PSF (dirty beam) for the protocluster G012.80 as a function of the distance from the PSF centre (in arcseconds). B3 spectral windows are shown on the left and B6 spectral windows are on the right. The solid lines use the .psf outputs from tclean and the dashed lines are the expected Gaussian clean beams (the FWHM is taken from the geometric mean of the beam major and minor axes). For the B3 spectral windows, the Gaussian clean beam is a good approximation to the PSF only within ∼50% of its FWHM. B3 spectral window 0 shows the largest deviation, resulting in a larger estimation of the respective Gaussian clean beam in tclean. The B6 spectral windows typically show a better correspondence between the PSFs and the Gaussian clean beam.