The process of sky/background fitting and subtraction is illustrated here for DDO 43 as an example. Upper left: V image of DDO 43. North is up and east to the left. This is displayed with a linear stretch from counts 2415 to 2445. Upper right: mask of objects not to be included in the fit of the sky/background. This is displayed 0 to 1, where 0 are the pixels not to be fit. Middle left: V image times the mask. The mask is applied in the fitting, but this image is given to make it clear what is being fitted in this case. This is displayed with a stretch from counts 2415 to 2445. Middle right: The fit to the sky/background times the mask. This is displayed with a stretch from counts 2415 to 2445 for direct comparison to the frame to the left. In this case, the fitting process used the Python package BACKGROUND2D with a 13 pixel BOXSIZE and a 7 pixel FILTERSIZE. Bottom left: V minus the fit to the sky/background. This is displayed with a stretch from counts −3 to 10.