[vsnet-chat 473] Re: C/1997 O1 (comet Tilbrook)

[Fraser Farrell <fraserf@dove.net.au>]

G'day all,

   >> Because the weather here is still cloudy, I am including this
   >>very approximate  orbit and ephemeris.  I know some vsnetters look
   >>at comets, so I hope you will  email me some observations to help
   >improve these numbers.  Please.... >

Silly me, I should have solved for a _parabolic_ orbit!  A new solution
including tonight's visually observed positions is:
T = 1997 Aug 4.45       peri = 355.6
q = 1.41 AU             node = 232.4
e = 1 (assumed)         incl = 106.4
This may be no better than my last orbit, but I live in hope :)

The preliminary orbit quoted in IAUC 6707 was:
T = 1997 Jul 16.560     peri = 339.104
q = 1.3855              node = 231.329
e = 1 (assumed)         incl = 114.115


Justin Tilbrook finally got another look at his comet this evening.  Magnitude
10.3v with 80" coma, distinct nucleus, and no tail - 20cm telescope.  I should
mention that Justin's observatory is surrounded by farms and vineyards so his
sky is very dark.  I only saw 20" coma.

Extrapolating the IAUC orbit backwards a few months helps explain why this comet
wasn't found earlier.  Although it has been over 60 degrees away from the Sun
since March,  it has spent most of the time cruising through Car, Vel, and Cen.
It finally escaped the Milky Way about 3 weeks ago, but southern observers know
what the weather's been like lately.


Further news on Comet Tilbrook will appear on the Astronomical Society of SA Web
site (http://vsnet.gist.net.au/assa/).


Interestingly, C/1997 O1 passed close to X Hor and R Car - two of my regulars -
before Justin nailed it on the R Crv/TV Crv chart.  My notebook reports that X
Hor was clouded out that week; and R Car was at 4th mag maximum so I was using
7x50's.  Now I'm _really_ depressed!! :)




cheers,
Fraser Farrell

http://vsnet.dove.net.au/~fraserf/   email: fraserf@dove.net.au
traditional: PO Box 332, Christies Beach, SA  5165, Australia

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