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Spectropolarimetry is the measurement of EMR polarization by wavelength. A spectropolarimeter, an instrument that makes such measurements, is often a spectrograph feeding into a polarimeter that is capable of separating a line of an image into polarized components. A CCD's two dimensions can display the wavelength over one dimension and two components of polarization across the other, so the CCD image holds polarization data by wavelength for a point source. A Wollaston prism is one optical device to separate the light into components by polarization.
Spectropolarameters are used on ground telescopes, and spacecraft including telescopes and planet exploration missions. Applications include detecting and mapping magnetic fields, and working out characteristics of the source of reflected or scattered EMR, such as from a planetary nebula, or an active galactic nucleus.