Example of an average effective direction in a facet. The red circles indicate calibrators. The central calibrator has a peak flux of 0.91 Jy beam⁻¹, while the next brightest non-calibrator source, approximately 16′ to the left, is 0.12 Jy beam⁻¹. Within the facet of the calibrator, the Jones matrices are mostly optimised in a direction of the calibrator, but this effective direction changes over time, baseline, and frequency.