These files use 2MASS as the astrometric reference catalog.
  http://www.ipac.caltech.edu/2mass/releases/allsky/index.html

These were made with the Astrometry.net tools as of rev 22478.

These packages makes use of data products from the Two Micron All
Sky Survey, which is a joint project of the University of
Massachusetts and the Infrared Processing and Analysis
Center/California Institute of Technology, funded by the National
Aeronautics and Space Administration and the National Science
Foundation.
