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Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 22 > Chapter 13: Spectroscopic Reference Material > First-Order Grating G230L

First-Order Grating G230L
Description
The G230L grating is used with the NUV-MAMA and has a relatively high throughput and a resolving power of ~500.
Recommended Uses
G230L is designed for observations where high spectral resolution is not required, but efficient, spatially resolved spectroscopy with full spectral coverage in the NUV is desired.
Special Considerations
Notice that the CCD G230LB grating mode also covers the NUV with comparable resolution; see “Comparison of G230LB and G230L” for a detailed comparison of these two grating modes in that wavelength regime.
 
Figure 13.30: Wavelength Range for the G230L Grating Settings
G230L Sensitivities
Table 13.9: G230L Throughputs and Sensitivities for a Point Source
Figure 13.31: G230L 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 plate scale in units of arcseconds per pixel and by the width of the desired slit in units of arcseconds.
G230L 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 13.32: Diffuse Source Signal-to-Noise as a function of STMAG for G230L
Figure 13.33: Point Source Signal-to-Noise as a Function of STMAG for G230L

Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 22 > Chapter 13: Spectroscopic Reference Material > First-Order Grating G230L

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