Strous-format scatter analysis for data B. Images: simultaneous blue- and red-wing images at Δλ = ±0.8 Å at the best-seeing moment (highest square in the lower graph of Fig. 2). First diagram: scatter contours for this image pair. The format is detailed in Sect. 2. The axis quantities are intensities in SST data units. The green box selects a specific low-density contour feature with the corresponding pixels outlined by green contours in the images. Second diagram: scatter contours for all such 252 image pairs in the data B sequence passing the seeing threshold, with the same axes and the green box repeated as location reference. Online image blinker: 1–2.