|STIS Instrument Handbook for Cycle 25|
The E230H grating is used with the NUV-MAMA and provides echelle spectra at a resolving power of ~114,0001 from 1620 to 3150 Å.A single E230H echellogram covers ~267 Å, over ~20-70 orders. The orders are spaced by only ~ 12.7 pixels (0.37 arcseconds) at 1650 Å and 47.2 pixels (~1.38 arcseconds) at 3100 Å. The grating must be scanned, with exposures taken at six distinct settings to cover the full spectral range of the grating.
λ/228,000 Figure 13.50: Wavelength Ranges for the E230H Grating Settings
Figure 13.51: E230H Point Source (left axis), and Diffuse Source (right axis) Sensitivities. Throughput curve traces the peaks of the blaze function for each order.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 13.52: Diffuse Source SNR as a Function of STMAG for E230HFigure 13.53: Point Source SNR as a Function of STMAG for E230H