The complete analysis of an image is fully automated (Fig. 1). Two passes are made through the data. During the first pass, a model of the sky background is built, and several global statistics are computed. During the second pass, image pixels are background-subtracted, filtered and segmented on-the-fly. Detections are then deblended, pruned (“CLEANed”), and enter the measurement phase. Finally, the measured quantities are written to the output catalog, after cross-matching with an optional input list.


Fig. 1 Layout of the main SExtractor procedures. Dashed arrows represent optional inputs.

The following sections describe each of these operations in more detail.