[vsnet-chat 1564] (fwd) The discovery of C/1998 P1 (Williams)

[Taichi Kato <tkato>]

From peter_williams@nykline.co.jp Thu Jan 21 13:03 JST 1999
Date: Thu, 21 Jan 99 13:44:26 +0900
From: "Peter Williams"<peter_williams@nykline.co.jp>
To: <tkato@kusastro.kyoto-u.ac.jp>
Subject: Comet C/1998 P1 (Williams)
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     Dear Taichi,
     
     Regarding your vsnet-chat 1559 of January 18, you asked about the 
     discovery of Comet C/1998 P1.  Below is the 'official story' which I 
     prepared for local Australian comet newsletters and periodical 
     magazine 'Sky & Space'.  This gives a personal account of events 
     leading to this discovery while on my way to observing the dwarf nova 
     EK TrA.  I trust you find this of interest and enjoyable.  It was a 
     very unexpected and pleasant surprise for me!  The text is stored on 
     my works computer so I send it from that location.  Please feel free 
     to distribute all or part through the vsnet-chat or other lists.
     
     Regards
     
     Peter Williams, Heathcote NSW
     pfwilliams@onaustralia.com.au
     
     
     
     
     
     THE DISCOVERY OF COMET C/1998 P1 (WILLIAMS).
     
     Peter Williams
     
     Most people like to complain about the weather and, well, I guess I'm 
     just like the rest.  August 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 9 days of August and I was 
     beginning to suffer the 'DTs' 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, and 
     sending the occasional total magnitude estimate to David Seargent of 
     the Australian Comet Section during this time.
     
     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 to catch up 
     on some of the brighter variable stars on my regular working list.
     
     A normal night's observing at Heathcote involves preparation under 
     subdued lighting, a naked eye nova search along the Milky Way followed 
     by a search to near magnitude 8 in two selected areas with the 10x50mm 
     binoculars.  This is followed by the binocular variables before moving 
     onto the telescopic stars.  Each observing session can last between 30 
     minutes and several hours.
     
     With the moon just two days after full there was a very narrow 'dark 
     window' before moon rise.  I had used this time for the binocular 
     variables.  After this I returned indoors to help with some domestic 
     duties and getting the children off to bed.  Domestic duties complete, 
     I sat down with my wife, Linda, and feeling rather tired thought I may 
     retire early for the night.
     
     However, having been clouded out for near two weeks I felt obliged to 
     show the 'right stuff' and check on the telescopic variables.  In 
     hindsight, this proved a wise decision.
     
     By 9.30pm local time and with the near full moon well above the 
     horizon, the roll-off roof of my observatory parted as I prepared for 
     observation with the 30cm F6 Newtonian reflector.
     
     Working through my usual sequence of variable star fields, I commenced 
     low in the south west with SY Mus and DI Cru, followed by 8 other 
     irregular and unusual stars in the Cru-Mus-Cen region.
     
     Then sweeping eastward at a low 72x magnification from Alpha Cir 
     towards the faint dwarf nova EK TrA, I almost fell of the three step 
     ladder used to reach the eyepiece as a bright comet-like object came 
     into view.
     
     'Oh gosh, what have we here?' or words to that effect I muttered, 
     knowing only too well there should be no fuzzy blobs in that area of 
     sky.
     
     A full millisecond or two later I forgot completely about EK TrA as 
     complete panic set in.  Was it clear in New Zealand?  Was it clear in 
     Victoria?  As I shuffled through my charts to find that for EK TrA, I 
     pondered who else may be observing this field that evening.  Having 
     located the chart I proceeded to plot the object's position then wait 
     and look for movement.
     
     At the time of discovery the comet appeared large, round  and diffuse 
     with no tail and a 13th magnitude stellar central brightening.  
     Through the 20x80mm binoculars it was estimated at magnitude 9.5 but 
     of somewhat smaller diameter than through the telescope at only 4 
     arcmin across.
     
     Within half an hour clear movement towards the north west was evident 
     so I moved indoors at near relativistic speed to seek independent 
     confirmation.  After several frustratingly unanswered phone calls, I 
     eventually raised David Seargent of the Australian Comet Section who 
     was able to provide verification.
     
     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 Central Bureau for Astronomical 
     Telegrams at the Smithsonian Astrophysical Observatory in Cambridge, 
     USA.  The CBAT replied the next day with a request for more 
     information and additional positions to allow for establishing a 
     preliminary ephemeris.
     
     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 
     fortunate clear patches which allowed me to relocate the comet and 
     establish an additional position.  This was duly emailed to the CBAT.
     
     Unknown to me, Gordon Garradd of Loomberah, near Tamworth, had learnt 
     of the comet through David Seargent and was busy measuring the comet's 
     position on CCD images obtained that night, providing the accurate 
     details needed by the CBAT. 
     
     IAUC 6986 was issued on Wednesday 12th August 1998 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 MacNaught 
     played an important part in verifying this comet.
     
     Looking back, however, this discovery was contributed to by a number 
     of fortunate circumstances.
     
     Firstly, the sky was clear and calm that evening after more than a 
     week of strong winds and driving rain.  Secondly, despite a near full 
     moon the decision was made to observe through the telescope.  Thirdly, 
     had I delayed going outdoors a little longer I may not have observed 
     the field of EK TrA.  Finally, had I not been monitoring a non-program 
     suspected variable a little to north of EK TrA, I may not have swept 
     northward to low magnification and onto the comet.
     
     Luck may have played its part.  However, I like to believe - tongue in 
     cheek - that I have been conducting a systematic search for comets, in 
     variable star fields, while looking in the wrong direction and under 
     full moon.  Clearly, my methods have been vindicated!

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