astrometry

from WordNet (r) 3.0 (2006)

astrometry
    n 1: the branch of astronomy that deals with the measurement of
         the position and motion of celestial bodies

from The Collaborative International Dictionary of English v.0.48

Astrometry \As*trom"e*try\, n. [Astro- + metry.]
   The art of making measurements among the stars, or of
   determining their relative magnitudes.
   [1913 Webster]