|Space Telescope Science Institute|
|COS Instrument Handbook|
As shown in Figure 6.3, the COS NUV channel is sensitive to wavelengths above 3200 Å, an important consideration when imaging red objects. For stars with effective temperatures above 6000 K, the effect is negligible, but it grows to about 20% at 5000 K, and below 5000 K it quickly becomes large.If you upload a spectrum into the ETC to calculate exposure time of an imaging exposure, whether for a target acquisition or a scientific observation, be sure that the spectrum spans the full range of wavelengths to which the NUV channel is sensitive, from about 1600 Å to 12,000 Å. Failure to do so can produce a misleading result.