There are several different techniques for producing the flat field, but they all share the goal of exposing the detector to uniform illumination. The image values in the resulting frame will be proportional to the pixel gains. Division of the object frames by the flat field will eliminate these variations. The calibration procedures assume that the voltage on the detector is linearly proportional to the incident flux. A plot of the relationship fot the detector in Omega Cass will be placed here.
Some pixels are more nonlinear and others less.
Observers who need accurate photometry will want to correct all their exposures for nonlinearity before proceeding with the standard data reduction. We recommend using a second or third order polynomial fit to each detector's response. A linearization matrix is not yet available. Dave Thompson prepared the corresponding finding charts and also a list of interpolated K' magnitudes . Troubleshooting If you get images like this, check the entrance window of the dewar if water is condensed.