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Two banks of 8 hollow-cathode tubes (a Th-Ar and a Cu-Ar set) are located above the focal surface for wavelength calibrations. The lamps illuminate a screen which folds into the beam when in use. Selection of the lamp type is made by swapping a cable connection near the instrument.
Flat field calibrations are made by pointing the telescope at a white spot which is mounted onto the side of the dome. A bank of quartz lamps, mounted on the telescope, illuminate the white spot.