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THE ASTRONOMER Electronic Circular No 856      1994 July 12 17.42UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England. Telephone/FAX(0256)471074 Int:+44256471074
INTERNET: GMH at AST.STAR.RL.AC.UK  or    GMH at GXVG.AST.CAM.AC.UK
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PERIODIC COMET SHOEMAKER-LEVY 9 (1993e)
R. M. West, European Southern Observatory, has measured the nuclei
on CCD images obtained during July 1-8 by O. Hainaut, R. Schulz,
M. Carollo, C. Alard and A. Cimatti with the 3.5-m New Technology
Telescope and 1.5-m Danish telescope.  Reductions were with the help
of southern Sky Atlas plates and provisional Hipparcos
reference-star positions provided by M. Perryman and C. Turon.
S. Nakano, Sumoto, Japan, has computed improved orbits and the
following times (corrected for light time) for the impacts on
Jupiter:
A = 21, July       16.826 UT;
B = 20,            17.113;
C = 19,            17.287;
D = 18,            17.483;
E = 17,            17.625;
F = 16,            18.014;
G = 15,            18.308;
H = 14,            18.805;
K = 12,            19.425;
L = 11,            19.919;
N =  9,            20.428;
P = 8 (= P2 = 8b), 20.624;
Q = 7 (= Q1 = 7a), 20.831;
R = 6            , 21.223;
S = 5,             21.627;
T = 4,             21.758;
U = 3,             21.907;
V = 2,             22.166;
W = 1,             22.330.

Comparison with computations by P. W. Chodas and D. K. Yeomans,
Jet Propulsion Laboratory, suggests that the uncertainty is now
around +/- 0.005 day for almost all these nuclei, the remaining
uncertainty being mainly because most of the earlier observations
were reduced using the STScI Guide Star Catalogue.
Using the tidal-disruption model of Z. Sekanina, Chodas and Yeomans
provide less certain impact times for lost and less well observed
fragments: J = 13, July 19.11 UT; M = 10, 20.24; P1 = 8a, 20.69;
Q2 = 7b, 20.81.  They add that a significant number of particles
beyond the eastern end of the nuclear train should now already have
begun to strike Jupiter.
IAUC 6017

Guy M Hurst







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