Source : Webster's Revised Unabridged Dictionary (1913)

Altazimuth \Alt*az"i*muth\, n. [Alltude + azimuth.] (Astron.)
   An instrument for taking azimuths and altitudes
   simultaneously.

Source : WordNet®

altazimuth
     n : an instrument that measures the altitude and azimuth of
         celestial bodies; used in navigation