Spectral resolution is crudely characterized by the FWHM (in pixels) of an unresolved spectral line.
Tables of spectral resolution (FWHM) as well as line spread function plots can be found in the instrument handbook.
For point sources, FWHM is relatively insensitive to aperture width, but spectral purity degrades with increasing aperture width.
Line Spread Functions (LSF) or instrumental profiles give the detailed distribution of light along the primary dispersion axis.
Turning off the FUV-MAMA repeller reduces LSF wings, but use of this available mode requires a strong scientific justification.