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A method of scanning a small wavelength interval of the optical spectrum using a narrow band interference filter and a moving axicon lens has been developed. It is suggested that this system could be used for the detection of lithium emission in the twilight in order to reduce the possibility of auroral contamination and provide wavelength identification of the signal. Fast auroral waves, previously identified in the absence of any auroral forms other than the arc from which they apparently emanated, have now been observed to occur during a pulsating aurora display. The waves were substantially the same type as those observed earlier and were differentiated from the pulsating patches by their fast southward motion across the sky and their greater latitudinal extent (up to 200 km). Some preliminary results of an attempt to find a mechanism for the generation of the fast auroral waves are presented. (Author)