As a rule of thumb, CASPIR and IRIS have can image to a magnitude limit
of 
in an hour, or 
in 20 minutes, given typical
Siding Spring seeing (for a point source). Spectroscopy requires that objects
be brighter that 
. More detailed calculations can be made using
the night sky brightnesses in Table 1, and sensitivities listed in the
manuals. Note that nearly all near-IR observations will be sky limited.