Hello all. I have been doing some work with the individual calexp files and understanding their rotation and coaddition into coadds and as part of the process was curious to know what the actual units (eg e-, adu etc) of the image returned as a calexp are. I am accessing coadds using the butler via calexp = butler.get("calexp", dataId=refs[0].dataId)), similarly to as is done in the tutorial. I’ve tried looking through the documentation, the LSST DC2 Release Notes, and the forum with no answer, sadly. I also do not see anything useful in the FITS headers (via calexp.getMetadata()). Worst comes to worst I could probably trace the pipeline out from original exposure through the calibration function and do dimensional analysis, but I was hoping someone here knew off the top of their head what the units of the calexp are. Thanks in advance!
Single frame images–what is returned by butler.get('calexp')–are in instrumental fluxes with units of “counts”, and can be converted to nanojansky via:
calibrated = calexp.photoCalib.calibrateImage(calexp.maskedImage)
See more notes about using the PhotoCalib object here: PhotoCalib has replaced Calib: welcoming our nanojansky overlords
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