Differences between Pan-STARRS and IGAPS g magnitudes as a function of position in the WFC image plane. Median values are plotted for each 250 × 250 pixel² bin. The mask applied for observations made within four different phases of UVEX data collection are shown. The diagonal hatched regions represent the placement of the inner g-band mask, while the dotted regions indicate the outer mask. Top-left: mask used for observations before June 2006. Top-right: mask for observations between June 2006 and December 2013. Bottom-left: mask for observations between December 2013 and March 2017. Bottom-right: mask for observations after March 2017.