... ARC 3.5m | ... 2.3 Taking DIS Exposures . ... Instrument Calibration . ... 5.3 Fringing in Red . ... DIS (Dual Imaging Spectrograph) is a medium dispersion spectrograph with separate red and blue channels. ... The optical path consists of a slit-mask assembly, a shutter, a dichroic with a transition wavelength around 5350 Angstroms, and two independent collimators and cameras for the blue and red sides. ... Typical DIS calibration exposures include wavelength calibration, flat fields, and bias...