Southern Tasmania is well placed near the southern pole to observe and photograph some of the magnificent  light shows known as the 'Aurora Australis'. During early November 2004, the conditions were just right when a massive class IV flare from a sunspot group sent highly charges particles in our direction. A class V flare is the maximum.  From my observatory near Hobart I am in a good location to set up equipment in readiness for such a display. The sun’s activity is constantly monitored by special solar observatories and early predictions can alert the media when a big event on the sun is likely to cause a significant auroral display. Such was the case in early November 2004 when X class flares were reported that was associated with a large sunspot group. The effects of these massive solar outbursts take approximately two days to reach the earths atmosphere, so some warning allows preparation time to get equipment ready, just in case!

 

From my Southern Cross Observatory near Hobart I have been using very sensitive video camera systems to observe and record faint auroral activity on a frequent basis, activity too faint to be seen by the human eye alone. The eye is a rather poor receptor in dim lighting and also has a very poor response to colour at these low levels. The increased sensitivity of modern video cameras which use CCD’s (charge coupled devices) instead of film, are ten to twenty time more sensitive than film - and it is this factor that I have exploited in capturing auroral activity in real time.

 

This technique is quite exciting as it produces a moving image recorded on tape or hard drive that can be studied at a later date. However, this technique has its limitations – the images are black & white and a single image from video tape makes a poor print image on paper.

 

With the advent of digital cameras, particularly single lens reflex cameras with interchangeable lenses & using wide angle lenses at full aperture setting with very short exposure times (2 to 5 seconds) opens up another way to photograph auroral displays in colour as a realistic presentation of what was actually observed with the naked eye. Many people have taken auroral photographs with the family camera loaded with the average film; usually 200 ISO a 50 mm lens and film with a time exposure of many seconds. While this  produces some pleasing images they are often not an accurate record because of the blurring effect of a long exposure coupled with rapidly moving light beams, curtains, ripples and so on.

 

As a scientific imaging specialist in a former life, I have always pursued accuracy and detail especially in challenging conditions. Capturing fast moving auroral light displays are just one of those challenges and with some careful preparation and modern electronic imaging technology / processing, I have managed to the results I wanted.

 

Because auroral activity is infrequent and not always predictable. there are not too many opportunities for practice runs and the results are not always up to par, especially with film. However, with a modern DSLR camera one can see almost immediately if the shot is OK and make adjustments to aperture and speed settings accordingly. Another advantage of the digital camera is the equivalent film speed rating that can be achieved from 100 to 1600 ISO, depending on the make and model of digital camera. Because of the structure of the CCD and its ratio of red, green and blue pixels, it is necessary to correct the images with suitable image processing and I use Adobe Photoshop, which works very well. There are other more specialised programs designed for astronomical work but these are not in everyday use by the casual photographer. A technique to reduce the ‘grainy effect of the very short exposures is to electronically ‘stack’ several images or use a noise reduction software for example ‘Noiseware’ and the free version produces excellent results.

 

 

The images shown here are just a small selection from 2004 & 2005.

Images kept small for dialup modem viewers. 

 

 Southern Cross Observatory