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Spectral Resolution

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.

Tabulated Line Spread Functions

1200 Å 1500 Å 1700 Å 2400 Å 3200 Å 5500 Å 7000 Å
G140L G140L G230L G230L G430L G430L G750L
G140M G140M G230M G230M G430M G430M G750M
E140M E140M E230M E230M      
E140H E140H E230H E230H      


Turning off the FUV-MAMA repeller reduces LSF wings, but use of this available mode requires a strong scientific justification.

Last Updated: 06/02/2023


HST Help Desk 

Please contact the HST Help Desk with any questions.