# 7.4.2 Estimation of Exposure Times for Spectroscopic Observations

The exposure times for FORCAST grism mode spectroscopic observations should be estimated using the FORCAST on-line grism exposure time calculator. This calculator can be used to calculate the signal-to-noise ratio (S/N) for a given "total integration time", to calculate the total integration time required to achieve a specified S/N, or to estimate the limiting flux for a desired S/N.

In either case, overheads should not be included, as SPT calculates them independently.