Schematic view (from left to right) of example nominal, extended, and secondary masks. For the extended and secondary masks, the respective nominal mask is represented with dashed lines. In this case, the nominal mask consists of 5 pixels, the extended mask has 19 pixels, and the secondary mask has 3 pixels. The red circle represents the target star, and the cyan triangle represents a nearby contaminant star that could be an EB. Nominal masks are used to extract target photometry and were built to have the lowest NSR. The extended masks are constructed by enlarging the nominal masks, typically by surrounding each nominal mask with a ring of one pixel. Secondary masks are typically smaller and are centered on the most problematic contaminant star in the window.