AAO image reference AAT 6. « Previous || Next »
Image and text © 1979 Anglo-Australian Observatory, photograph by David Malin.
By pointing a camera towards the south (or to the north in the northern hemisphere) at night, we can record the paths of stars which never set. They appear to circle the apparent position of the Earth's axis of rotation projected on the sky. The elevation of this position above the local horizon indicates our local geographical latitude, about 30 degrees south at Siding Spring. The angle swept out by the arcs is an indication of the exposure time, which was about 10.5 hours on 400 ISO colour film. This kind of exposure is only possible from an extremely dark site. More information on relationship between the measurement of time and star trails is in the caption to a similar picture here.
During the long winter nights observers using AAT occasionally peer outside to inspect the weather and as they walk around the dome their lights produce the irregular lines at the catwalk level. The upper part of the dome is however illuminated by the light of the natural night sky and stars alone. Click here for bigger image and more about star trail photography is here.
Related images
AAT 5. Star trails setting behind the AAT
MISC 18. The view to the north from Siding Spring
MISC 5. Dawn and evening twilights reflected in the AAT dome
MISC 12. Orion's belt rising over the lights of Coonabarabran
MISC 14. South celestial pole star trails
MISC 13. North celestial pole star trails
MISC 15. North and South celestial poles star trails
MISC 11. Orion star colours, step-focus technique
MISC 22 The AAT dome from the Director's Cottage.
MISC 16. Southern Cross and Pointers, star colours - step-focus technique, long trails
MISC 17. Pinatubo dust colours the twilight
MISC 23 Southern Cross and Pointers, star colours - step-focus technique, short trails
MISC 19. Sunset 'star' trail, the track of the setting sun
MISC 6. Moonset into cloud over the Warrumbungle Range
MISC 7. Star trails around the AAT dome, after Pinatubo sunset
MISC 8. Aurorae Australis