  Angular differential imaging (ADI) (Marois et al. 2006) is an observational
technique in high contrast imaging where the telescope is used in pupil
tracking mode so that the image of the sky rotates with respect to the optical
surfaces. Bright "speckle" light caused by optical errors remains fixed in the
image, while planets and disks rotate with the sky. The resulting dataset is
then post-processed to remove the speckles, de-rotated to undo the sky motion,
and median-collapsed to create a final data product. The postprocessing
algorithms to remove the speckles are an active area of research and beyond the
scope of this note. We consider the derotation and median-combination, where we
show gains in signal-to-noise ratio are possible with a small change to the
algorithm.
