CGS4 Readnoise

For CGS4 the readnoise from the calibration system is first divided by a factor to take multiple non-destructive reads into account:

$$RNE = RN / \frac{3.8 + 3.5 * e^{-1/8 * N_{ND}}}{3.8 + 3.5 * e^{-1/8}}$$

where RNE is the readnoise per exposure, in electrons, RN is the readnoise in electrons, and N_ND is the number of non-destructive reads.

The formula used to determine the variance due to readnoise is:

$$V_{RN} = \frac{RNE^{2}}{N_e * gain^{2}}$$

where RNE is the readnoise per exposure, in electrons, N_e is the number of exposures per integration, and gain is the detector gain in electrons per ADU.