Table 5.5 contains Johnson-Cousins
V magnitudes for unreddened O5 V, A0 V, and G2 V stars, generated using the Exposure Time Calculator. WFC and HRC values used the parameters CR-SPLIT=2, GAIN=2, and a 0.2 arcsecond circular aperture. For the SBC, a 0.5 arcsecond circular aperture was used. An average sky background was used in these examples. However, limiting magnitudes are sensitive to the background levels; for instance, the magnitude of an A0 V in the WFC using the F606W filter changes by ±0.4 magnitudes at the background extremes.
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