A guide to IRCS grism spectroscopy exposure times 

Even with the 0.15'' slit, the spectral resolution of the IRCS grisms is not high enough to work effectively between the OH lines. Good removal of these lines is an essential part of obtaining high quality scientific data, and this is usually performed by nodding the target along the slit on a timescale no longer than the typical variability timescale of the OH lines.