When we got back from our little drive around to try and find the source of the glow, as we got out of the car I looked up to the sky as I normally do and noticed something in the sky. What I saw was a straight line across the sky. This is the 25W Laser which is projected from the William Herschel Telescope to provide an artificial guide star for the adaptive optics system which allows the removal of the effects of the air turbulence which is what causes the stars to twinkle.
30sec Exposure showing Laser
2 1/2 minute Exposure showing Laser tracking stars