FreeLists / az-observing / [AZ-Observing] Comet Ikeya-Zhang's Wrong-way Tail

[Tom Polakis <polakis@xxxxxxx>]

Just getting back from a good, long observing weekend in the Chiricahua
Mountains.  Through my 20-inch scope at 110x, Comet I-Z showed a broad coma
nearly 10' across, and a ray tail about 4' wide and 2 degrees long.  What
struck me was the position angle of the tail.  It is currently pointing due
west, or roughly 60 degrees away from sunward.  I made observations on the
nights of June 7 and 8.  The tail was faintly visible in a 70mm Pronto
refractor.

I called comet enthusiast Chris Schur when I got home.  He has a sort of
anti-tail fetish, and runs a DOS program that spits out the Earth's orbital
plane crossing, knowing longitude of the ascending node.  I had Voyager III
do the same thing, and have posted a diagram at:

http://www.psiaz.com/polakis/comets/I-Z_anti-tail.jpg

We both came up with June 25 for orbital plane crossing.  At this time, the
anti-tail will point directly sunward.  Before and after the 25th, the dust
trail is skewed, as we are seeing now.

I haven't visually seen a really prominent anti-tail since one of
Bradfield's many comets, in 1988.  Still more than two weeks before plane
crossing, this one is showing some promise.  The comet couldn't be much
more favorably placed for those who like observing during nighttime hours.

Interest in the comet seems to have fallen off, and the show is just now
getting good.

Tom

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Tom Polakis
Tempe, AZ
Arizona Sky Pages
http://www.psiaz.com/polakis/
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