Astrometry engine aims to create correct, standards-compliant astrometric
meta data for every useful astronomical image ever taken, past and future,
in any state of archival disarray.

The engine will take any image and return the astrometry world coordinate
system (WCS) -- i.e., a standards-based description of the (usually
nonlinear) transformation between image coordinates and sky coordinates --
with absolutely no "false positives" (but maybe some "no answers").  It
will do its best, even when the input image has no -- or totally incorrect
-- meta-data.

WWW: http://www.astrometry.net/