Thanks for the kind comments all of you.
Akira, when getting the aurora into view with a telephoto lens it is enlarged enough to make a curtain of pretty homogeneous color, mostly green. Also, the one minute exposure will tend to blur it out. The final image resulted from an additive stack of a single frame that contained the aurora and another image that was the result of a 17 image stack that did not contain the aurora. The single aurora frame was heavily processed to suppress aurora and stars in the right hand part where the aurora was weaker, and strong color noise reduction was applied to this frame to avoid noise in the green part. Normally a single 1 min exposure would not have that sharp distinction between the aurora and the background. Here is the 17-image stack without the aurora:
300mm PF at f/4.5, stack of 17 one minute exposures @ ISO 1600.
This is what the aurora looked like in a single wide angle frame a bit later, Andromeda is located behind the aurora curtain below the two downward pointing branches at the golden intersection from the right and 1/3 from the bottom, looks lie a blurry star (sorry for the non-interesting foreground, image just meant for documentation):
Somewhat cropped frame at @ 12 mm f/4, 20s, ISO 1600
