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XD at Low Resolution (R<1800)

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Grating/Camera configurations:

32 l/mm grating and short blue camera or 10 l/mm grating and long blue camera

Resolving power:
(λ/Δλ)

1800 either with with short blue camera and 0.3 arcsec wide slit or with long blue camera and 0.1 arcsec wide slit. Lower resolving powers if wider slits are used.

Typical uses:
(...and limitations)

Full coverage 0.85-2.5µm spectra in short slits: 7 arcsec long for the 32 l/mm grating, short blue camera and its (SXD) prism; 5 arcsec long for the 10 l/mm grating, long blue camera and its (LXD) prism. There is no inter-order contamination. One can also use the long blue camera with the SXD prism and the 7 arcsec slit, but then the wavelength coverage is 1.2-2.5µm.

The orders are positioned on the array so as to avoid the patches of bad pixels. The short slits are sufficiently long that for point-like sources it is possible to nod the telescope while keeping the source in the slit and thus obtain sky subtracted-spectra for which the source is observed 100 percent of the time. For sources larger than a few arc-seconds it is necessary to nod the telescope to blank sky.

Typical raw image of a faint galaxy showing sky emission in orders 3-8 (left to right, with wavelength increasing downwards)

Reduced spectra of a standard star in orders 3 through 8 covering 0.85 to 2.5 microns are shown below. Click on each spectrum to enlarge.