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Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 22 > Chapter 13: Spectroscopic Reference Material > First-Order Grating G750L

First-Order Grating G750L
Description
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.
Recommended Uses
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.
Special Considerations
Fringing in the CCD compromises the realizable signal-to-noise longward of 7500 if contemporaneous fringe flats are not obtained (see Section 7.3).
 
Figure 13.2: Wavelength Range for the G750L Grating Setting
G750L Sensitivities
Table 13.3: G750L Sensitivities & Throughputs for a Point Source
Figure 13.3: G750L Point Source (left axis), and Diffuse Source (right axis) Sensitivities
Note
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.
G750L Signal-to-Noise
Note:
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-/. The curves are labeled with exposure times in seconds
 
Figure 13.4: Diffuse Source Signal-to-Noise as a Function of STMAG for G750L. λ Fiducial = 7500 .
Figure 13.5: Point Source Signal-to-Noise as a Function of STMAG for G750L

Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 22 > Chapter 13: Spectroscopic Reference Material > First-Order Grating G750L

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