Fig. 1. Panel (A): Image of the 1/2m focal length Ebert-Fastie spectrometer at the Auroral station in Adventdalen, Svalbard. (1) is shutter, (2) instrument housing, (3) cooler for the photo multiplier tube, (4) tripod, (5) photo multiplier amplifier and discriminator, (6) light protective cell, (7) high voltage supply, (8) driver to shutter motor, and (9) stepper motor connected to grating shaft. Panel (B): Three-dimensional optical diagram of the spectrometer. (1) is entrance slit, (2) concave mirror, (3) grating, (4) exit slit, (5) collector lens, (6) photo multiplier tube, and (7) broadband order sorting filter.