|STIS Instrument Handbook for Cycle 25|
The G140M grating mode is used with the FUV-MAMA and has a spectral range from 1150 to 1700 Å.With a resolving power R~10,000, a single exposure with this grating covers only 55 Å. The grating must be scanned, with a series of exposures taken at 12 distinct settings to cover the full spectral range.The G140M grating mode is designed for observations where spatially resolved, long slit, spectroscopy is desired at relatively high spectral resolution over a limited region of the UV spectrum.
Figure 13.42: Wavelength Ranges for the G140M Grating SettingsTable 13.12: G140M Throughputs & Sensitivities for a Point Source
Point source sensitivity assumes full transmission (zero slit losses). Diffuse source sensitivity assumes a 0.1” wide slit. To convert point source sensitivities to diffuse source sensitivities multiply the point source values by the grating spatial plate scale in units of arcseconds per pixel and by the width of the desired slit in units of arcseconds.The top axis displays constant Fλ values corresponding to the STMAG units (V+STMAGλ) on the bottom axis. Recall that STMAG=0 is equivalent to Fλ = 3.63E-9 erg/cm2/s/Å. The curves are labeled with exposure times in seconds.