comparison spectrumThe spectrum of one or more known substances under terrestrial conditions that is used in astronomy as a standard of comparison for investigating spectra of celestial objects; it provides, for example, a zero Doppler shift.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
comparison spectrum[kəm′par·ə·sən ‚spek·trəm]
A line spectrum whose wavelengths are accurately known, and which is matched with another spectrum to determine the wavelengths of the latter.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.