Spectroscopists may need to consider separately two different sensitivities--the sensitivity to spectral features in the individual line channels and the accuracy with which the continuum can be estimated from the line-free channels. The need for individual channel sensitivity normally dominates, however. The calculation uses Equation 3, with replacing . It may also be appropriate to express the sensitivity in terms of brightness temperature by converting from mJy per beam area to temperature units assuming a Gaussian beam of area .
Use of narrow channel bandwidths often implies that sensitivity, rather than u-v coverage, considerations determine for high-resolution synthesis spectroscopy, so that observations >12 hours long may be needed. Spectroscopic observations may also need long integrations on the calibration sources to achieve enough sensitivity.