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Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 22 > Chapter 13: Spectroscopic Reference Material > First-Order Grating G230M

First-Order Grating G230M
Description
Like the G230L grating, the G230M grating is used with the NUV-MAMA; it has a spectral range from 1650-3100 , however, with a resolving power R~10,000 a single exposure with the G230M grating covers only 90 , and the grating must be scanned, with a series of exposures taken at 18 distinct settings to cover the full spectral range.
Recommended Uses
The G230M grating mode is designed for observations where spatially resolved, long slit, spectroscopy is desired at relatively high spectral resolution covering a limited region of the NUV spectrum.
Special Considerations
Notice that the CCD G230MB grating mode also covers the NUV with comparable resolution. See “Comparison of G230MB and G230M” for a detailed comparison of these two grating modes in that wavelength regime.
Figure 13.34: Wavelength Ranges for the G230M Grating Settings
G230M Sensitivities
Table 13.10: G230M Throughputs & Sensitivities for a Point Source
Figure 13.35: G230M 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.
G230M 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 13.36: Diffuse Source Signal-to-Noise as a Function of STMAG for G230M
Figure 13.37: Point Source Signal-to-Noise as a Function of STMAG for G230M

Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 22 > Chapter 13: Spectroscopic Reference Material > First-Order Grating G230M

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