|STIS Instrument Handbook for Cycle 25|
Like the G430L grating, the G430M grating is used with the CCD and has a spectral range from 3020–5600 Å.Since a single exposure taken with this grating covers only 286 Å the grating must be scanned, with a series of exposures taken at 10 distinct settings, to cover the full spectral range of the grating.The G430M grating mode is designed for observations where spatially resolved, long slit spectroscopy is desired at relatively high spectral resolution (R~6000) over a limited region of the NUV or optical spectrum.
Figure 13.14: Wavelength Ranges for the G430M Grating Settings
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 seconds.Figure 13.16: Diffuse Source SNR as a Function of STMAG for G430MFigure 13.17: Point Source SNR as a Function of STMAG for G430M