To illustrate the difficulties in analysing the gray-scale images,
here are two images captured almost simultaneously at the
Athabasca University Geophysical Observatory
with a panchromatic images (left) and Rainbow (right). The fields-of-view
are slightly different as are the orientations of the images. Nevertheless,
both images show an auroral display behind the clouds. The bright object to the
right of the centre is the Moon. There is some bright aurora in the lower
part of the images. Notice how distinctive the green aurora is in the
colour image. The gray-scale image does not provide enough information alone:
a sequence of images is needed to verify the movement of the aurora in order
to determine that auroral emission is present. |