CGS4
CGS4 is a 1-5um multi-purpose 2D grating spectrometer containing a
256x256 InSb array, installed in a cryostat which is cooled by liquid
nitrogen and closed cycle coolers. Four gratings are available, two of
which are installed in the cryostat at any one time. They are a 40
l/mm grating which provides resolving powers of 500-2200, a 75 l/mm
grating, a 150 l/mm grating which provides resolving powers of roughly
3000-8500, and a 31 l/mm echelle which provides a resolving power of
about 37,000 (8 km/s). The 75 l/mm grating is rarely used
thesedays. These resolving powers are achieved with the 300 mm focal
length camera optics and a one-pixel-wide slit, which provide a scale
of 0.6 arcsec/pixel for the two moderate resolution gratings and
roughly 0.41x0.90 arcsec/pixel for the echelle (0.41 arcsec/pixel in
the direction of the dispersion).
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