The Discovery of Comet Williams

Most people like to complain about the weather and, well, I guess I'm just like the rest. August in Sydney is usually associated with strong winds but this year they were accompanied by driving rains which produced flooding in many areas of eastern New South Wales.

My backyard observatory at Heathcote, on the southern extremity of suburban Sydney, was partially flooded with 3cm of water when a nearby drain became blocked by garden debris. Nearly 170mm of rain was recorded at Heathcote during the first nine days of August and I was beginning to suffer withdrawal from a lack of starlight.

Perhaps better known for the observation of variable stars, I have been fortunate enough to also observe a number of comets over the years, beginning with Comet Bennett, the Great Comet of 1970. During this time, I have also sent the occasional observational report to David Seargent-comet writer for Sky & Space magazine and head of the Australian Comet Section.

A normal night's variable star observing begins with preparation under subdued lighting. Then, my observing pattern starts with a search for naked-eye novae along the Milky Way, followed by a deeper nova search to around magnitude eight in two selected areas using 10x50 binoculars. Then I monitor a number of variables with the binoculars before switching to the telescope and moving on to some fainter stars. Each observing session can last between 30 minutes and several hours.

That fateful night

Monday, August 10, was the first clear night of the month so, although feeling tired after arriving home from work a little later than usual, I ventured outdoors after dinner with binoculars in hand in order to catch up on some of the brighter variable stars on my regular working list.

On this particular night, with the Moon just two days past full, I had only a very narrow 'dark window' available before moonrise. I used this time for the binocular variables. Then, I went indoors to help with some domestic duties and getting the children off to bed. That done, I sat down with my wife, Linda, and feeling rather tired thought I might retire early for the night.

However, as I had been clouded out for nearly two weeks, I felt obliged to show the 'right stuff' and check on the telescopic variables. In hindsight, this proved a wise decision.

By 9:30 pm, with the nearly-full Moon well above the horizon, the roll-off roof of my observatory parted as I prepared to observe with my trusty 30cm f/6 Newtonian reflector. Working through my usual sequence of variable star fields, I commenced low in the southwest with SY Muscae and DI Crucis, followed by eight other irregular and unusual stars in the Crux-Musca-Centaurus region.

Then, sweeping eastward at a low 72x magnification from Alpha Circinus towards the faint dwarf nova EK Triangulum Australis (EK TrA), I almost fell off the step-ladder I was using to reach the eyepiece as a bright, comet-like object came into view.

"Oh my gosh, what have we here?", I muttered ... or words to that effect. I knew only too well there should be no fuzzy blobs in that area of the sky.

A full millisecond or two later I forgot about EK TrA as I realised what I had found. Complete panic set in. Was it clear in New Zealand? Was it clear in Victoria? As I shuffled through my charts to find the one for EK TrA, I desperately tried to think of who else might be observing this field that evening. Having found the chart, I plotted the object's position. Then I waited and watched for any sign of movement.

At the time of discovery the comet appeared large, round, and diffuse with no tail, and a 13th-magnitude star-like centre. Through my 20x80 binoculars I estimated its total magnitude to be around 9.5 and, at only four arcminutes across, of somewhat smaller diameter than when seen through the telescope.

Within half an hour, clear movement towards the northwest was evident. I moved indoors at near the speed of light to seek independent confirmation. After several frustratingly un-answered phone calls, I raised David Seargent. He went outside for a look, and was able to verify what I had seen.

At this stage even Linda-who is generally content to view the moon once every second year-left the warmth and comfort of bed to become only the third person on Earth to view the comet.

David kindly emailed the co-ordinates and magnitude estimates to the International Astronomical Union's (IAU) Central Bureau for Astronomical Telegrams (CBAT) at the Smithsonian Astrophysical Observatory in Cambridge, Mass., USA.

The longest day

The CBAT replied the next day with a request for more information and additional positions, to help in establishing a preliminary orbit. I had never realised how long the daylight hours are as I waited for nightfall!

Tuesday night was essentially cloudy at Heathcote, except for several clear patches which (fortunately) enabled me to relocate the comet and establish an additional position. This was duly emailed to the CBAT.

Unbeknown to me, Gordon Garradd of Loomberah, near Tamworth, had learnt of the comet through David Seargent and was already busily measuring its position on CCD images he obtained that night, thus providing the accurate details needed by the CBAT.

IAU Circular number 6986 was issued on Wednesday, August 12, announcing the discovery of Comet 1998 P1, much to the relief of all concerned.

Many emails and telephone calls from well wishers have since been received, topping off several days of intense excitement. My two minutes of fame have certainly been an experience I will long remember. The help, encouragement, and co-operation of local identities such as David Seargent, Gordon Garradd, and Rob McNaught played an important part in verifying this comet.

Looking back, however, this discovery was helped along by a number of fortunate circumstances.

First, the sky was clear and calm that evening after more than a week of strong winds and driving rain. Secondly, despite an almost full Moon, I made the decision to use my telescope. Thirdly, had I delayed going outdoors a little longer I might not have been able to observe the field of EK TrA. Finally, had I not been monitoring a non-program suspected variable a little to north of EK TrA, I might not have swept the telescope northward at low magnification and onto the comet.

So, luck may have played its part. However, I like to believe-tongue in cheek-that for all these years I have actually been conducting a systematic search for comets, in variable star fields, while looking in the wrong direction and under a full Moon. Clearly, my methods have been vindicated!

Peter Williams is a member of the Sutherland Astronomical Society, and one of the country's most experienced variable star observers, with 30 years observing under his belt. Since 1991 he has written the Variable Views column in Sky & Space, and in 1996 was awarded the Berenice Page Medal by the Astronomical Society of Australia, the nation's body of professional astronomers. Peter-"WPX"-has contributed data to AAVSO for well over a decade.