318 12. Spectrometry: Definitions and Basic Principles
arrayed, the gain in observing efficiency is significant. We discuss some of the
optical characteristics of fiber-fed spectrometers in Chapter 15.
12.4.
SLITLESS SPECTROMETERS
Based on the discussions in Section 12.2, the relations for slitless spectro-
meters are easily found. The major differences for the slitless mode are: (1) the
image size of a stellar source is set by atmospheric seeing or diffraction rather
than a slit; (2) the anamorphic magnification is one in all practical configurations;
and (3) the diameter di is the beam size at the dispersing element.
Thus the relations in
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