|STIS Instrument Handbook for Cycle 25|
The G750L grating is used with the CCD. It has high throughput but low resolving power (~500), and is designed for efficient, full spectral coverage. The grating has one prime tilt setting.This grating is recommended for observations where high spectral resolution is not required, but efficient coverage in the red portion of the optical is desired.Fringing in the CCD compromises the realizable signal-to-noise longward of 7500 Å if contemporaneous fringe flats are not obtained (see Section 7.3).
Figure 13.2: Wavelength Range for the G750L Grating Setting
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 (cross dispersion) 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 secondsFigure 13.4: Diffuse Source Signal-to-Noise as a Function of STMAG for G750L. λ Fiducial = 7500 Å.