Table B.5 gives sigma sensitivities for each channel of a fully-sampled spectrum taken in a 1 hour observation using the standard 75M and 240M gratings. The wavelength range covered by such an observation is included. For wavelengthsa longer than 2.5um the sensitivity scales inversely with aperture size, here assumed to be a 3.5" square. The sensitivity changes rapidly with wavelength through the L window, and is further influenced by atmospheric transmission which is low near the ends of most bands, around 1.1 - 1.18um, between 2.9 and 3.4um, and at certain other wavelengths. In addition, bright objects are subject to seeing noise that can increase the time required by a large factor if the seeing at the relevant wavelength exceeds 3-4". M spectroscopy is not recommended.
Table B.5: FIGS limiting magnitudes for a one-hour observation
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