Fig. 8. Image of an LETG
spectrum of a very bright X-ray source, the nova XTE J1118+480.
Only the shortest wavelengths are shown.
- Bright spot in center: the source (i.e., 0th order of the spectrum).
- Bright diagonal line extending corner to corner:
the main dispersed spectrum (1st and higher orders).
- Bright line perpendicular to the main spectrum:
cross-dispersion spectrum of 0th order, caused by the LETG
- Faint six-pointed star pattern in the center: diffraction of 0th
order by the triangle-pattern coarse-support structure.
- Faint fan of whiskers on either side: cross-dispersion orders
caused by the fine-support structure. The main dispersed
spectrum is 0th order of the cross-dispersion spectrum.