Central Bureau for Astronomical Telegrams
IAUC 4958: 1989c1
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Read IAUC 4959
Circular No. 4958
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
COMET AUSTIN (1989c1)
Improved parabolic orbital elements from MPC 15857:
T = 1990 Apr. 9.9138 ET Peri. = 61.5709
Node = 75.3043 1950.0
q = 0.349428 AU Incl. = 58.9370
1990 ET R.A. (1950) Decl. Delta r m1
Mar. 10 1 22.62 -10 39.1 1.544 0.868 4.8
15 1 29.23 - 5 54.8
20 1 35.65 - 0 42.7 1.411 0.663 3.5
25 1 41.42 + 5 02.7
30 1 45.60 +11 24.8 1.253 0.466 1.7
Apr. 4 1 46.30 +18 17.9
9 1 40.47 +25 06.0 1.046 0.350 0.0
14 1 26.13 +30 36.1
19 1 05.41 +34 01.3 0.808 0.435 0.4
24 0 41.60 +35 35.6
29 0 15.77 +35 47.0 0.600 0.626 1.4
May 4 23 46.88 +34 48.2
9 23 12.24 +32 27.8 0.418 0.831 1.8
14 22 27.66 +27 58.9
19 21 28.23 +19 41.9 0.275 1.030 1.8
24 20 13.00 + 6 04.6
29 18 52.75 - 9 44.4 0.251 1.220 2.4
June 3 17 44.40 -21 21.8
8 16 54.82 -27 50.8 0.389 1.402 3.9
The above positions should be good to better than 15' in mid-April,
but the error could still be around 1 deg in mid-May. The magnitude
has been computed from m1 = 4.5 + 5 log delta + 10 log r, which is
in good agreement with recent observations. R. H. McNaught, Siding
Spring Observatory, has derived the following even more optimistic
formula, which satisfies 28 observations 1989 Dec. 17-1990 Jan. 27
with an rms error of 0.3 mag: m1 = 3.8 (+/- 0.4) + 5 log delta +
13.7 (+/- 1.3) log r. It certainly would seem that 1989c1 has the
potential to be the best comet since 1976. On the other hand, the
disappointing display of comet 1973 XII serves as a reminder that
cometary brightness is notoriously unpredictable. The prediction for
comet 1989c1 on IAUC 4926 was deliberately intended to be conservative,
but it is worth noting that the 7.5 log r term utilized is often quite
characteristic of 'new' comets from the Oort Cloud, as 1973 XII and
1989c1 both appear to be.
1990 February 2 (4958) Brian G. Marsden
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