The green airglow emission is very similar to the famous green we see in the northern and southern lights. It is produced by the same oxygen molecules as the green aurora, just on a lower level that is hard to see with the naked eye. This is a natural color image, with the air glow subtracted from the upper part of the image to reveal the Milky Way.
10x10 second images, stacked using Sequator to avoid star blurring and to increase the signal to noise ratio. Did a better job of maintaining accurate colors this time. The bright magenta blob in the center is the Lagoon Nebula, which I hope to get some close-ups of next year,