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THE ASTRONOMER Electronic Circular No 979       1995 Aug  3 20.05UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England. Telephone/FAX(0256)471074 Int:+44256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK             GMH at AST.STAR.RL.AC.UK
WORLD WIDE WEB                    http://www.demon.co.uk/astronomer
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COMET C/1995 O1 (HALE-BOPP)
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.
IAUC 6194
R. H. McNaught, Anglo-Australian Observatory, reports that he has
located an image of this comet on a 50-min U.K. Schmidt R survey
plate obtained by C. P. Cass on 1993 Apr. 27.  During the exposure
the comet, then 13.1 AU from the sun, would have moved 3".7 to
the southwest, and the image is consistent with this.  It has
the appearance of a slightly diffuse and slightly elongated star
image within a very faint coma 0'.4 in diameter.  The total and
uclear magnitudes are about 18 and 19, respectively, based on
this being a good-quality plate with a presumed limit of 21.
The position is 9' from that given by the parabolic elements on
MPEC 1995-P01, which are now improved on MPEC 1995-P02:
                    Epoch = 1995 Oct. 10.0 TT
     T = 1997 Apr.  1.3922 TT         Peri. = 130.4405
     e = 0.996348                     Node  = 282.4733  2000.0
     q = 0.916702 AU                  Incl. =  88.8797

                    Epoch = 1997 Mar. 13.0 TT
     T = 1997 Apr.  1.6416 TT         Peri. = 130.6678
     e = 0.994441                     Node  = 282.4729  2000.0
     q = 0.913023 AU                  Incl. =  89.4142

These orbital elements, satisfying 248 observations with mean
residual 0".6, lead to (1/a)orig = +0.00456 +/- 0.00016 AU-1,
indicating that the comet is not on its first pass from the Oort
Cloud.  However, McNaught adds that he could not locate the comet
on a plate taken on 1991 Sept. 1, when an inverse-square law
would have put the comet 1.0 mag fainter than in 1993.
IAUC 6198

Guy M Hurst