Entrance Slits, Diffraction Gratings, and Optical Bench 2.3. EUV Filters 3. Sky Coverage, Spectral Resolution, and Sensitivity 4. Data Analysis, Data Products, and Archiving 1. At slightly higher temperatures, emission lines at shorter wavelengths become important.
Light enters the spectrograph through the array of nine entrance slits shown at lower right.
Each slit illuminates a single diffraction grating. Each grating is cylindrical, so the light is focused only in the plane of dispersion. All nine gratings disperse their spectra onto a common, flat detector plane. Zero-order light does not strike the detector and can be baffled separately. The rotated orientation of the off-axis channels introduces a slight mismatch between the ideal focal surface and the common detector plane at the ends of the bandpass.