Left panel: Flux distribution of all pixels within the sky apertures (see text). The distribution closely follows a normal distribution, showcasing that our method of selecting sky apertures is robust. The black error bar shows the observed standard deviation of the distribution, and the other bars show different noise estimates. The shaded extensions to the bars show the effect of applying the drizzle correlation factor (R and R_ap, for σ_medpix, and σ_aper, respectively). Comparing the extended green bar to the extended cyan bar then give very similar results. The black bar, gives the total statistics for all the pixels contained within our apertures. The purple bar shows the noise as inferred from the image error extension (σ_ERR). Right panel: The effect of aperture size on the noise estimates. We use an aperture radius of 0$\stackrel{″}{.}$225 for the final noise estimate which is indicated by the vertical dashed black line. The noise estimates in this panel are all corrected for correlation (except for σ_ERR).