AipyBugReport

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Bug Reports[edit]

Here you can write descriptions of any bugs you encounter in AIPY.

Bug[edit]

There is an algorithmic bug in how mk_img.py and mk_map.py work together to do facet imaging. Currently, mk_img.sh generates images in the epoch of the data, and then mk_map.py precesses the center of the images to the epoch of the map that is to be generated (usually J2000). The problem is that precessing the phase center of the map and the doing the normal RA/DEC pixel extrapolation from phase center does not produce correctly precessed coordinates. For example, if a precession involves a slight rotation of north into east, precessing the phase center will only fix translational errors, not rotational. The solution is probably to make sure that the epoch encoded by mk_img.sh is always the epoch of the data, and for mk_map.py to generate full coordinates for all pixels in the map at the epoch. Then the coordinates of each pixel should be independently precesses to the epoch of the map before gridding into the map.

Reported by: Aaron Parsons

Assigned to: Aaron Parsons