Reduced low resolution spectra for all slit orientations (﹩\psi _{s}=0^{\circ },\ 18^{\circ },\ldots ,\ 162^{\circ }﹩, numbered in red). The intensity ﹩w_{i}( \rho ,v) ﹩, coded according to the color intensity code shown by the triangles down the middle of the figure, is shown as a function of velocity (abscissa: v with ticks at 100 km s⁻¹) and position along the slit (ordinate: ﹩\tilde{m}﹩, major ticks spaced by 1^{﹩\arcmin﹩}). The positive axis of the velocity coordinate points away from the observer, and the positive axis of the slit coordinate points toward the numbers in Fig. 5. The large orange cross indicates the true origin of the coordinate system centered on the pulsar at ﹩v=0﹩, cf. eq. (4). The light gray ring with a dot at its center indicates the projection of the spherical shell volume (﹩R_{\mathrm{in}\,}=65^{\prime \prime }﹩, ﹩R_{\mathrm{out}\,}=90^{\prime \prime }﹩) found by the fit. The colors are assigned with respect to the "average bright spot mixture of intensities," which is coded gray [center of the triangle, ﹩( \mathrm{H}\,\thinspace{:}\thinspace \mathrm{N}\,\thinspace{:}\thinspace \mathrm{S}\,) =( 0.18\thinspace{:}\thinspace 0.42\thinspace{:}\thinspace 0.40) ﹩; in the average hydrogen is much stronger], while the corners of the triangles correspond to pure H, N, or S as indicated on the triangle at the top of the figure. Intensity is coded relative to each reduced spectrum as the fraction of the maximum intensity of the given reduced spectrum. For respective maximum values, see text. The minimum intensity seen is ~5% of the maximum intensity, which is significantly above noise; remember, however, that because of line interference the deconvolution is not unique (compare Fig. 7).