Fig. 5From: Imaging of polar cap patches with a low-cost airglow camera: pilot observations in Svalbard, NorwayRelationship between the absolute optical intensity values at zenith from the two ASI systems during the interval of polar cap patches shown in Fig. 4. Note that we only used data from 2010 to 2300 UT to remove the effect of large increase of emission intensity due to the appearance of aurora near the zenith in the first 10 min of the intervalBack to article page