Transmission curves for the 2MASS optical path (thick line), including the telescope mirror reflectivity, dewar window, antireflection coatings, dichroics, filters, and the NICMOS detector quantum efficiency, but excluding atmospheric absorption. The thin line shows the model atmospheric transmission for the mean observing conditions at Mount Hopkins, computed using the USAF PLEXUS code and binned to a resolution of 0.002 μm.