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Natural Wonder
Preparation
Equipment and Techniques
The Outback
Eclipse Day
Totality
Note: Under no circumstances should the Sun be observed without safe solar filters. Please seek professional advice before engaging in any form of solar observing.
Natural Wonder
A hungry serpent? The evil spirits of darkness? Or just an extraordinary astronomical coincidence? What is it that turns the Sun dark and transforms day into an eerie kind of pseudo-night? Questions like this have been pondered throughout the eons and have led to countless mythologies attempting to explain what causes a total eclipse of the Sun. Only in the last few hundred years has the mysticism and terror associated with a solar eclipse been replaced by a rational explanation firmly based in celestial mechanics. An eclipse, once thought to bring death and disease, now has disciples from all over the world converging to stand in the shadow of the moon.
In 2002, Australia was to witness a total solar eclipse for the first time since 1976. For the 30 precious seconds known as 'totality', the Moon would obscure the blinding light of the solar disk to reveal the Sun's usually invisible faint outer atmosphere, the corona. With powerful magnetic fields and temperatures soaring to over a million degrees, the deceptively delicate glowing structure of the corona is the main attraction. On 4th December, the Moon's shadow would strike the coast in the Great Australian Bight, race across outback South Australia at over 100km per second, before disappearing over the horizon in far western Queensland.
Preparation
While poring over the eclipse literature, excitement grew with each new delightfully detailed image I saw - some showing wisps of the pearly white corona streaming into space, some with large red gaseous blobs exploding from the solar surface like fire, and others showing the exquisite pattern of sparkling light known as Bailey's Beads. None, however, captured more than a few seconds' worth of an eclipse that usually lasts for over two hours. NASA scientist Fred Espenak in particular had perfected the art of recording an entire eclipse on one frame of film to create a dramatic sequence of crescent Suns trailing across the image like a shooting star. Determined to also capture such a unique image, I began planning and practising months in advance to maximise the chances of success.
Equipment and Techniques
Chewing up its fuel at the rate of four million tonnes per second, the Sun emits enough radiation to burn the retina within milliseconds, even for observers standing 150 million kilometres away. Eclipse glasses were therefore crucial to the prevention of any loss of vision associated with high levels of radiation. The camera, also susceptible to 'retinal' burns, had to wear its own eye protection in the form of a solar filter. A neutral filter of logarithmic density 4.0 was used to reduce the incident light by a factor of 10,000. Exposures were carefully determined using a combination of experimental results and modelling techniques, due to the diminishing apparent brightness of the Sun near sunset. The camera settings for the exposure of totality were based on previously published guides for eclipse photography.
Having amassed nearly every possible eclipse coordinate to four decimal places, timing data down to milliseconds, and GPS readings with an accuracy of a few metres, planning when to take the exposures and where to point the camera still involved some head-scratching. Finally it was decided that seven exposures on either side of totality would be taken each at five minute intervals, giving the image overall symmetry and balance. The altitude and azimuth of the sun at the required times were plotted onto a scaled diagram, to ensure that the entire sequence would indeed fit into the one frame.
The Outback
Driving down a little-known dirt road near the vast dried-out salt of Lake Everard, South Australia, the landscape was red, barren and desolate. Being 200 kilometres north east of Ceduna, Lake Everard was predicted to be cloud free. However, for two days before the eclipse, there was no blue sky to be seen. Nonetheless, a site on the leeward side of the only vegetation for miles that would afford any protection from the incessant winds was selected. On eclipse eve, a full dress rehearsal was conducted to ensure that all the camera gear was working properly, and that the sun would not set before the final image was due to be taken. Now all that was left to do was to wait.
Eclipse Day
Waking up early, there was a distinct feeling that something amazing was going to occur. A small crowd of a hundred or so temporary residents had migrated into the Lake Everard region in anticipation. The crisp morning sky, devoid of cloud, brought with it the promise of clear evening skies, however the wicked wind had decided to blow up a storm.
With only two hours to go, all equipment was setup and thoroughly checked, the tripod weighed down with sand bags and new batteries installed. One hour to go before the curtains opened on nature's greatest drama, and there was little more to do than sit back and enjoy the view.
18:41. The eclipse had begun. Not until a minute or so later was a slight nick in the solar limb obvious. Before long it was time to commence photographic proceedings. As practised the previous day, the Sun was placed in the top right corner of the viewfinder ten minutes before the first exposure and allowed to track into the frame.
It was now 19:05. The timer was running and the first exposure taken. Excitement grew with just over half an hour left until totality. Every camera setting was checked. Then double checked. Had the multiple exposure switch not been
over-ridden before any of the exposures, the film would have wound on and rendered all the hard work and preparation useless.
The timer slowly ticked its way toward totality. Fifteen minutes to go and the light began to fade noticeably. An eerie feeling pervaded the atmosphere. Suddenly, the last of the crescent Sun exposures had been made and it was time to remove the solar filter, since this was not needed during the low light of totality.
19:35. Less than five minutes now. Tension mounted while the light faded. Everything turned orange-grey, and the sky darkened. Not long now, only a few seconds left, and before we knew it
..
Totality
Woooooow! Look at that! The long pearly wisps of the corona streamed into space like outstretched fingers and contrasted against the pure black disk of the Moon. Was this the 'eye of God'? My heart was thumping, things were happening quickly. I regained composure, checked the timer and tripped the cable release at mid-totality. All the while my eyes were transfixed on this hole in the sky, but despite all the preparation, my brain was still confused as to what was actually happening. Why had it gone dark in the middle of the day? I wondered. I was now able to fully appreciate how a total eclipse of the Sun could cause so much fear and anxiety to so many of our ancestors.
Before long, a single bright spot of glistening light exploded from the edge, and combined with the corona formed the much celebrated 'Diamond Ring' effect. It lingered for a number of seconds before my retinas reminded me that it was time to look away. Eclipse glasses were replaced and far too soon totality was all over. The thin crescent of the Sun had re-emerged and signalled the end of the most amazing 30 seconds of my life.
With adrenaline still flooding through my veins, the solar filter was replaced and the first of the post totality exposures made. It was now 19:45 and sunset was only half an hour away. The rest of the exposures ran smoothly as more and more of the Sun gradually re-appeared, and the eclipse drew to a close. With the dissapearance of the Sun's last rays below the horizon, came the end of an experience that no words could adequately describe, one that will forever remain vivid in my mind. But for now the painfully long wait to have the film developed had begun.
Having been fortunate enough to witness a total eclipse first hand (first eye?), I cannot recommend strongly enough that every possible effort be made to see at least one total solar eclipse in one's lifetime. Not even a passing interest in science is required to enjoy and be moved by the experience of totality and the sight of the Sun's corona.
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