[IAUC] IAUC 8777: C/2006 W3; C/2006 U7 [25139-2007/05-R1]

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                                                  Circular No. 8777
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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COMET C/2006 W3 (CHRISTENSEN)
     E. J. Christensen reports his discovery of a comet on Catalina
Sky Survey images obtained in good seeing with the 0.68-m Schmidt
telescope (discovery observation tabulated below); four 60-s
exposures showed a 15" coma extended very slightly toward p.a.
70-100 deg.  Following posting on the Minor Planet Center's 'NEOCP'
webpage, several astrometric CCD observers have commented on the
object's cometary appearance.  Stacked 15-s images obtained by L.
Buzzi and F. Luppi (Varese, Italy, 0.60-m f/4.6 reflector) on Nov.
19.1 UT show a 10" coma elongated in p.a. 80 deg with a 25" tail in
the same direction.  P. Birtwhistle (Great Shefford, Berkshire,
England, 0.40-m f/6 Schmidt-Cassegrain reflector) writes that his
images from Nov. 19.1 show the object to be distinctly diffuse and
only moderately condensed, with the center of light slightly offset
toward the west in a 14" coma (no tail).  J. McGaha (Tucson, AZ,
0.62-m f/5.1 reflector) reports that his 120-s exposures on Nov.
19.4 show a 9" coma elongated in p.a. 35 deg, with no apparent
nuclear condensation or tail.  J. G. Ries (McDonald Observatory,
0.76-m reflector) notes that his R-band images on Nov. 19.4 show an
asymmetric diffuse coma that is more prominent on the side opposite
to the comet's direction of motion.

     2006 UT             R.A. (2000) Decl.       Mag.
     Nov. 18.40414    7 00 04.24   +46 16 11.3   18.1

The available astrometry, the following very preliminary orbital
elements, and an ephemeris appear on MPEC 2006-W42.

     T = 2008 Dec. 25.327 TT          Peri. = 154.652
                                      Node  = 109.832   2000.0
     q = 1.46888 AU                   Incl. = 121.736


COMET C/2006 U7 (GIBBS)
     Additional astrometry of this comet (cf. IAUC 8769) reveals an
elliptical orbit (the following elements taken from MPEC 2006-W18):

     T = 2007 Feb. 10.974 TT          Peri. =   6.897
     e = 0.63310                      Node  =  57.906   2000.0
     q = 4.40745 AU                   Incl. =   6.992
       a = 12.01272 AU     n = 0.023672     P =  41.6 years

                      (C) Copyright 2006 CBAT
2006 November 20               (8777)            Daniel W. E. Green