AAO image reference MISC 29. « Previous || Next »
Image and text © 1977-2002, Australian Astronomical Observatory, Photograph by David Malin.
There are some nights when the weather is perfectly clear, there is no Moon and yet the sky is not dark. One would not notice this anywhere except in a location devoid of significant artificial light. Siding Spring Observatory (SSO) in outback Australia is such a place.
This was intended to add to my collection of telescope domes photographed at night. Some others are listed below. But this night was unusually bright, in spite of being, clear, moonless and cloudless from horizon to horizon. The picture was exposed for several hours using a familiar setup I knew would give me good star trails against a dark sky. When the film was developed the sky was as you see here, a curious greenish yellow.
The picture was made in 1977, which was around the time of a solar maximum and the likely explanation is that the Sun was active at the time, bombarding the upper atmosphere with energetic particles. These are usually funnelled by the Earth's magnetic field into aurorae, concentrated at higher latitudes than SSO. And sometimes not. This kind of effect is being recorded more often in the era of the digital camera, which is much more sensitive to faint light than any film camera was. I have no detailed explanation of the effect, but it is real, and appeared on other photographs I took at around the same time.
MISC 8. Aurora Australis
MISC 18. The view to the north from Siding Spring
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