EXT vs. EXT_STAT plane for recovered clusters where clusters have been separated by input count rate. The continuous line at EXT_STAT = 33 shows the cut for the C1 selection and the dashed line at EXT_STAT = 15 shows the cut for the C2 selection. The continuous line at ext =5′′ shows the cut in extent for both the C1 and C2 selections. If a source is found in more than one tile, the detection with the highest value of EXT_STAT is shown. Panel a: tiles; input count rate 0.1 count s^-1. Panel b: tiles; input count rate 0.05 count s^-1. Panel c: tiles; input count rate 0.01 count s^-1. Panel d: tiles; input count rate 0.005 count s^-1.