I cloned meas_astrom to meas_extensions_astrometryNet, made a new origin for it (in order to retain history for all files), then pruned both the old and new packages. If I did this correctly then no library file or test should be duplicated in the two packages.
I then updated the code in the new package to use the new naming, and all existing code I found that uses astrometry.net code (which includes some code in pipe_tasks and obs_monocam, both updated). I filed
DM-10242 to remove astrometry.net usage from pipe_tasks.
I also took a cleanup pass for Doxygen errors and pep8-related issues in meas_astrom and meas_extensions_astrometryNet.