Offsets between the measured location of each slitlet edge and its ideal position (for a specific band, rotator angle, and instrument temperature). The locations are calculated from the polynomial fits to each edge, for a single row of pixels across the detectors. Left edges are plotted as red diamonds, right edges as blue squares. The dotted lines indicate the separation between IFUs, and the dashed lines between the 3 instrument segments. An offset of 1 pixel is equivalent to 18 μm at the detector. Top panel: offsets calculated for the ideal case that the slitlet widths and spacings should be perfectly uniform across each segment (i.e. how far the edges differ from the location expected, based on the average slitlet width and spacing on that detector). Bottom panel: offsets derived for each IFU individually, i.e. based on the mean slitlet width and spacing per IFU. The distinct pattern (e.g. in IFU 3) is a direct imprint of the opto-mechanics.
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