Exposure times vs. flux estimates at signal-to-noise ratio = 10 in NIRCam images can be obtained using the Pandeia JWST Exposure Time Calculator (ETC) Python engine.
Parent page: NIRCam Predicted Performance
The Pandeia Exposure Time Calculator Old should be used for all observation planning. This article provides ETC results using the Python engine to loop through many calculations of signal-to-noise ratio (SNR) for various readout specifications and resulting exposure times, given assumptions detailed below. These calculations are then interpolated to determine depth (SNR = 10) vs. exposure time. The script is available on Github.
Depth vs. exposure time
The NIRCam Imagingoverview and NIRCam Sensitivity articles show SNR = 10 sensitivity estimates for imaging in all NIRCam filters given a total exposure time of 10 ks (166.7 minutes = 2.78 hours). Figure 1 shows similar estimates for a range of exposure times in seven wide filters and one medium filter.
JWST's background model varies with the target coordinates (RA, Dec) and time of year. These calculations assume the fiducial "1.2 × MinZodi" (1.2 times the minimum zodiacal light) background at RA = 17:26:44, Dec = -73:19:56 on June 19, 2019, as used in the NIRCam Imaging article. The background model for these observations must be generated using the online ETC GUI and then imported into the Python ETC engine.
Recommended readout patterns and exposure times used for the calculations on this page are described below. They are based on ETC calculations that show these to yield optimal signal-to-noise ratios for a given exposure time. RAPID 1, BRIGHT2, SHALLOW4, MEDIUM8, and DEEP8 yield high signal-to-noise ratio most efficiently and are preferred to maximize depth. The other readout patterns (BRIGHT1, SHALLOW2, MEDIUM2, DEEP2) may be preferred in some cases, for example, to provide a greater dynamic range (with a shorter first group) to sample bright stars before saturation.
When reading out the full detectors in both modules, RAPID and BRIGHT2 are limited to four groups, DEEP8 is limited to 20 groups, and all other patterns are limited to 10 groups. The table below gives the full range of recommended readout specifications for exposure times between 42.9 and 4176.6 s. The final two columns assume four such exposures.
Table 1. Recommended readout specifications for maximal depth in a given exposure time