Comparison of measured Hα using HST to JWST estimates. (a) Profile of H α from HST STIS (black) across the front compared to that derived – see text – from F187N (blue) and F405N (green). (b) The ratio of Hα emission estimated from JWST F187N (black) and F405N (blue) extracted from apertures matched exactly to HST STIS profile. In both plots, 0 on the x-axis corresponds to the edge of the PDR – see Sect. 5.1 – for profile cut 3 (which corresponds to the location of the JWST IFU and HST STIS long slit footprints).