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IAUC 6194: C/1995 O1

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                                                  Circular No. 6194
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

     The following improved parabolic orbital elements, from
MPEC 1995-P01, are based on 208 observations July 24-Aug. 1:

     T = 1997 Apr.  1.810 TT          Peri. = 129.956
                                      Node  = 282.339   2000.0
     q = 0.92819 AU                   Incl. =  89.779

These elements are still somewhat uncertain but indicate minimum
approach distances of 0.75 AU to Jupiter on 1996 Apr. 5 and 1.32 AU
to the earth on 1997 Mar. 23.

     Total visual magnitude estimates: July 26.22 UT, 10.8 (A. Hale,
Cloudcroft, NM, 0.41-m reflector); 27.19, 10.7 (Hale); 28.15, 10.7
(Hale); 28.24, 9.9 (R. Keen, Mt. Thorodin, CO, 0.08-m reflector);
28.94, 10.3 (J. Carvajal, Madrid, Spain, 0.44-m reflector);
29.31, 10.5 (C. S. Morris, Lockwood Valley, CA, 0.26-m reflector);
29.93, 10.2, (K. Hornoch, Lelekovice, Czech Republic, 0.35-m reflector);
30.28, 10.5 (C. S. Morris, Pine Mountain Club, CA, 0.26-m reflector);
30.29, 10.9 (Hale); 30.96, 10.4 (Carvajal).  Prediscovery
observations--especially negative prediscovery observations--of the
comet would be useful.

     W. Offutt, Cloudcroft, NM, reports that his CCD imaging with a
0.6-m reflector suggests that the northward "tail" mentioned on IAUC 6188
appears to be the maximum extension of an asymmetric coma and that,
although not all of the images were identically exposed, the coma seems
to have been shrinking over the course of the past week.  The position
angle of this maximum extension, its extent from the nucleus, its extent
on the opposite side of the nucleus, and the coma width perpendicular to
the extension, are as follows: July 24.19 UT, 14 deg, 154", 81", 218";
24.33, 9 deg, 154", 51", 202"; 25.15, 23 deg, 149", 55", 179"; 25.26,
13 deg, 138", 53", 188"; 28.18, 13 deg, 138", 41", 180"; 29.14, 2 deg,
109", 38", 172"; 31.19, 10 deg, 111", 39", 161".  In all cases, the
edge of the coma is least clearly defined near the position angle of
maximum extension and is most clearly defined in the opposite direction.
Commenting on the above, Z. Sekanina, Jet Propulsion Laboratory,
suggests that the observations are of a spiral coma, similar to the
halo sometimes displayed by comet 29P/Schwassmann-Wachmann 1 after an
outburst, the shrinking and the diffuseness in the direction of maximum
extension apparently products of a rapid fading of the halo's outer limits.
There seems little question that comet C/1995 O1 has had an outburst, and
it may grow fainter for some time.

1995 August 1                  (6194)              Brian G. Marsden

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