Sunset 'star' trails from Siding Spring
AAO image reference MISC 19.     « Previous || Next »

Sunset 'star' trails from Siding Spring
Image and text © 1990-2002, Australian Astronomical Observatory, Photograph by David Malin.

Like the Moon and stars, the sun rises and sets, and for the same reason. The sun is a star like any other, but it is much closer, for which we are eternally grateful. However, making a long exposure of the sun is much more difficult than making a star trail, but that's just what this is.

The trusty Hasselblad (a medium format film camera) was set on a tripod with its standard 80mm Planar lens set to f/16. It was loaded with 200 ISO Ektachrome (slide film) because that's all I had. It was also fitted with a neutral density filter with an attenuation (dimming) factor of 10 million (equivalent to ND 7), made simply by mounting Wratten ND 3 and ND 4 filter gels together in a screw-on filter mount.

The shutter was opened before the sun appeared in the frame and was left open all afternoon, probably five hours. Once the sun had set, the shutter was closed, the ND filter removed and, without winding-on the film, a short exposure was made of the after-sunset horizon, probably 1/25 at f5.6 or f/8. The flares around the sun trail are where it passed behind high cloud and they are greenish because the Wratten filters are not truly neutral and even the slightest colour cast would be evident with this amount of neutral density over the lens. Wisps of high cloud remain in the sunset scene.

The picture was taken from the catwalk of the AAT dome and the mountains in the foreground are part of the Warrumbungles. The same range features in a night-time version of a similar scene, showing the moon setting into cloud.

Related images
MISC 11. Orion star colours, step-focus technique
MISC 16. Southern Cross and Pointers, star colours - step-focus technique, long trails
MISC 23  Southern Cross and Pointers, star colours - step-focus technique, short trails
MISC 32. Antares and Jupiter, defocused star trails

galaxies | emission nebulae | reflection nebulae | dark nebulae | planetary nebulae | star clusters | stars | supernovae
50 Favorites | Messier objects | Repro conditions | Images site map | AAO images page

Updated by David Malin, 2012, March 17