rms photometric scatter, σ, in parts per thousand as a function of W146 magnitude. Each point corresponds to a single light curve, with the rms scatter normalized to the baseline (unmagnified) flux in each case. The blue circles are the total expected noise from the simulations of R. F. Wilson et al. (2023; Figure 9 top panel, which are normalized to a 0.5 hr exposure time), and the magenta line is a linear fit to the lower envelope of formal uncertainties for unmagnified data points (that excludes any noise in the reference image or the PSF fitting). The left panels (a) and (c) are for (unmagnified) baseline data points, and the right panels (b) and (d) for magnified data points between 1620 < t < 2700 minutes. The top panels (a) and (b) are for the simulated data set of 192 images (2 days), and the lower panels (c) and (d) are for a data set of 672 images (1 week).