The layout of the IDS is shown in Figure . The main components are:
Table: Characteristics of the IDS echelle grating
Table: Characteristics of the IDS gratings with the 235 mm camera
Table: Characteristics of the IDS gratings with the 500 mm camera
Along the direction of the slit (i.e. perpendicular to the dispersion direction), the focal lengths of 235 and 500 mm imply slit to detector reduction factors of 5.43 and 2.55 respectively, and hence scales at the detector of 29.4 and 13.8 arcsec/mm.
Along the dispersion direction, the slit to detector reduction factor is more complicated, since it depends on the grating angle. Tables and give the slit width in arcsec which projects to 45 microns at the detector, when each grating is used at its central wavelength.
The same tables also list the dispersion provided by each grating and camera combination. It can be seen that a wide range of dispersions is available, from 7 to 270 Å/mm.