I took this from the shore of Lake MacDonald in Glacier National Park at about 2 AM. My only interesting sight line was North towards Stanton Mountain (left) and MT Vaught (right). I took several test shots to get the focus, exposure and framing correct while trying to preserve my night vision. I was surprised to see the purple glow coming from behind the mountains because it was imperceptible in person.

Taken on my Sony A7Riii with Sony's 24mm f/1.4, 25 seconds, ISO 200. The camera was mounted on a tripod and a wireless shutter was used.

This is a single image, no stacking. In lightroom I raised the exposure, shadows, texture and saturation. I lowered the highlights and blacks with minor adjustments to other sliders.