The Collaborative International Dictionary of English v.0.48:

Spectroscopy \Spec*tros"co*py\, n.
   the art and science dealing with the use of a spectroscope,
   and the production and analysis of spectra; the action of
   using a spectroscope.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

spectroscopy
    n 1: the use of spectroscopes to analyze spectra [syn:
         spectroscopy, spectrometry, spectroscopic analysis,
         spectrum analysis, spectrographic analysis]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "spectroscopy":
   astrogeology, astrognosy, astrography, astrolithology, astronomy,
   astrophotography, astrophysics, celestial mechanics, chromatics,
   chromatography, chromatology, chromatoscopy, colorimetry,
   electron optics, gravitational astronomy, infrared spectroscopy,
   meteoritics, microscopics, microscopy, optical physics, optics,
   optometry, photography, radar astronomy, radio astronomy,
   solar physics, spectrography, spectrometry, spectrophotometry,
   spectrum analysis, stargazing, stellar photometry, stereoscopy,
   telescopy, uranography, uranology, uranometry