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IAUC 8909: 8P; C/2008 A1

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                                                  Circular No. 8909
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     J. K. Harmon, M. C. Nolan, and E. S. Howell, Arecibo
Observatory; and J. D. Giorgini, Jet Propulsion Laboratory,
obtained 300-m-resolution radar imaging of comet 8P/Tuttle on Jan.
2-4 using the Arecibo Observatory 12.6-cm planetary radar.  The
nucleus is a strongly bifurcated object, possibly a contact binary,
with two roughly spherical lobes measuring 3 and 4 km in diameter
(+/- 25 percent).  Following the changing rotation aspect from
night to night and within the 2.5-hr observing sessions gives a
preliminary estimate of 7.7 +/- 0.2 hr for the rotation period.  In
addition to the nucleus echo, there is a weak echo component from
large (> cm-sized) coma grains.
     Visual total-magnitude and coma-diameter estimates by J. J.
Gonzalez, Asturias, Spain:  2007 Dec. 26.77, 6.1, 15' (6x30
binoculars); 30.79, 5.6, 25' (naked eye); 2008 Jan. 3.79, 5.1, 30'
(naked eye); 6.78, 5.2, 30' (4x30 monocular); 9.84, 5.3, 30' (naked

     R. H. McNaught reports his discovery of a comet (discovery
observation tabulated below) on CCD images taken with the 0.5-m
Uppsala Schmidt telescope at Siding Spring Observatory; the comet
shows a moderately condensed circular of diameter 30".  Following
posting on the Minor Planet Center's 'NEOCP' webpage, other
astrometric CCD observers have commented on the object's cometary
appearance, including J. Young (Table Mountain Observatory, 0.61-m
f/16 Cassegrain reflector), who reported a 12" round coma in poor
seeing conditions on Jan. 11.3 UT.  E. Guido and G. Sostero,
Castellammare di Stabia, Italy, write that their 27 co-added 60-s
unfiltered exposures from Jan. 11.3 (remotely using a 0.25-m f/3.4
reflector near Mayhill, NM, U.S.A.) show a broad fan-shaped coma of
diameter nearly 30", elongated toward the northeast.

     2008 UT             R.A. (2000) Decl.       Mag.
     Jan. 10.57306    6 35 32.46   -43 45 47.5   15.2

The available astrometry, the following preliminary parabolic
orbital elements, and an ephemeris appear on MPEC 2008-A48.

     T = 2008 Nov.  3.860 TT          Peri. = 337.102
                                      Node  = 285.853   2000.0
     q = 1.51069 AU                   Incl. =  88.620

                      (C) Copyright 2008 CBAT
2008 January 11                (8909)            Daniel W. E. Green

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