grating is used with the FUV-MAMA
and provides echelle spectra at a resolving power of ~114,0001
from ~1140 to 1700 Å
A single E140H
echellogram covers ~210 Å over ~50 orders. The order separation is ~16 pixels (0.47 arcseconds) at 1150 Å and ~36 pixels (1.05 arcseconds) at 1700 Å. The grating must be scanned, with exposures taken at three distinct settings to cover the full spectral range of the grating.
Note that while the spectral format of the
1234 Å setting extends down to 1133 Å, the throughput becomes vanishingly small below about 1140 Å.
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.