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HiPERCAM / hipercam

Python package for handling HiPERCAM data
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package needs updating to accommodate COMPO #109

Closed StuartLittlefair closed 1 year ago

StuartLittlefair commented 1 year ago

With the commissioning of COMPO, changes are needed to the handling of apertures in the HiPERCAM pipeline.

This is because the injected image does not share the orientation of the main science image. The injected image is flipped w.r.t to the main image so that a $(x, y)$ shift for stars on the science image corresponds to a $(-x, -y)$ shift in the injected star and vice-versa.

Something like the following changes are probably necessary:

  1. Apertures need to be labelled as "COMPO" apertures, in the same way we can currently set apertures as reference apertures
  2. I propose COMPO apertures can also be reference apertures, and be linked to by other apertures. This seems essential in the use case where the COMPO aperture is the only useable u-band aperture, for example. It might, however, lead to poor photometry since the PSFs may not match.
  3. When placing apertures, the first step is often to apply the shift of the reference aperture in order to get a rough position. We need to take account of the flipped coordinate system when doing this.