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Sky subtraction

For templates that do not use chopping. please refer to the description given for SW data as the steps are identical.

For templates that use chopping, the typical observing sequence is ABBAABBA... etc. One first groups the frames into AB pairs and subtracts one image from another. This will result in an frame with one positive image and two negative images. The positive image will have a flux which corresponds to 2*DIT seconds.

Christopher Lidman