Airglow is a little-known phenomenon that can produce a surprisingly green sky, with a little red (if you take time exposures when the airglow is bright. The images here have some digital processing, in which I strove to preserve the background-to-stellar brightness and color. A time-lapse video of the scene is now posted at: https://vimeo.com/73254759 For more airglow info, a concise description is at http://www.atoptics.co.uk/highsky/airglow2.htm