Currently the AOS algorithm takes a pair of defocal images (containing images at the same field location as in comCam, or different field locations as in corner sensors of lsstCam). In each image it detects defocal point sources - donuts (either using the provided WCS information via reference star catalog, or convolving with donut template). The list of donuts is trimmed given their blending, or degree of vignetting. Donuts detected from intra and extra-focal exposures are "paired up" (currently in no particular order), and for each pair the AOS algorithm provides a list of Zernike coefficients that describe the wavefront. In turn we combine these to provide a single average wavefront estimate for each sensor to the optical feedback controller.
In contrast, the donut images from a given sensor could also be combined into a single "stacked" extra-focal and intra-focal donut, which would then provide a single stacked-donut Zernike estimate.

This ticket is to compare the first approach ("pairing") to the second approach ("stacking"). Find the difference (if any) between Zernikes estimated via paired-and-combined vs stacked-donuts. Check the dependence on intensity (eg. sources at 15th mag, 16th mag, 17th mag).

then paired In a single defocal Compare the output of averaging the Zernike