In cases where users select an extraction region over more than one CCD, the algorithm to correct TS changes completely. We have to deal with light curves coming from different detectors and therefore, we have to take into account all possible detector problems for each CCD. The key point in these cases is to calculate the effective area per CCD that it is being used in the extraction region.
We make a per CCD correction assuming that the counts come from a point source. If one of the CCDs contain a significan background contribution, then this algorithm won´t be right. Because of this, we encourage users to apply background subtraction in order to perform all corrections properly.
epiclcorr corrects the TS using the following algorithm.
If the user does not apply background subtraction, the source TS correction could overestimate the background contribution in cases where background counts are higher or similar to the source counts.
