Fig. 4From: Imaging-based observations of low-latitude auroras during 2001–2004 at Nayoro, JapanExample of an aurora image with the horizontal coordinates determined by using the described procedure. The five stars used in this procedure are indicated by the circles and labeled by their intrinsic names. The original image of this figure is that of Fig. 1a (the event that occurred on March 31, 2001)Back to article page