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IAUC 8979: P/2008 QP_20

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IAUC number

                                                  Circular No. 8979
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)

     R. E. Hill reports his discovery of a comet on Catalina Sky
Survey unfiltered CCD images taken with the 0.68-m Schmidt
telescope, the object showing a well-condensed coma of diameter
6"-8" and a narrow 18" tail in p.a. 250 deg in four stacked 30-s
exposures in 3"-4" seeing (discovery observation tabulated below,
though with magnitude added from Sept. 23.279 UT image); his
stacked 60-s images from Sept. 24.3 show the comet to be well
condensed with an elongated nuclear condensation with coma size 12"
x 20" and a narrow 4' tail in p.a. 260 deg.  Following posting on
the Minor Planet Center's 'NEOCP' webpage, numerous other CCD
astrometrists have reported this object to show cometary appearance,
and at this point, K. Smalley (Minor Planet Center) identified
Hill's comet with an apparently asteroidal object discovered by
LINEAR and designated 2008 QP_20 on MPS 255263 (discovery
observation also tabulated below).  G. Muler (Lanzarate, Spain,
0.30-m Schmidt-Cassegrain reflector) writes that fifteen co-added
130-s exposures on Sept. 24.06 show a tail about 29" long in p.a.
245.2 deg.  J. E. McGaha (Tucson, AZ, U.S.A., 0.62-m f/5.1
reflector) reports that a 180-s exposure from Sept. 24.2 shows a
bright, round 7" coma with a narrow 44" tail in p.a. 243 deg.  H.
Devore measured a 52".5 tail in p.a. 241 deg from exposures taken
by R. Holmes (Charleston, IL, U.S.A., 0.61-m f/4.0 astrograph) on
Sept. 24.34-24.36.  E. Guido, Castellammare di Stabia, Italy, notes
that forty unfiltered co-added 60-s exposures taken remotely by G.
Sostero, P. Camilleri, and himself (0.25-m f/3.4 reflector located
near Mayhill, NM, U.S.A.) on Sept. 24.4 show a coma about 10" in
diameter and a narrow tail about 30" long in p.a. 233 deg.  D. T.
Durig (Sewanee, TN, U.S.A., 0.30-m f/2.5 Schmidt-Cassegrain
reflector, Sept. 24.4, twenty 120-s co-added exposures) reports a
tail about 65" long in p.a. 245 deg.  A. C. Gilmore and P. M.
Kilmartin (Mt. John 1.0-m f/7.7 reflector, Sept. 24.5, poor seeing)
write that the object shows a stellar head and a tail about 40"
long in p.a. 240 deg.

     2008 UT             R.A. (2000) Decl.       Mag.   Observer
     Aug. 25.39837    1 35 21.33   +18 23 41.1   20.7   LINEAR
     Sept.23.26302    1 48 57.76   +24 38 26.1   17.7   Hill

The available astrometry, elliptical orbital elements (T = 2008
Nov. 2.277 TT, e = 0.50670, q = 1.72410 AU, P = 6.53 years, Peri.
= 71.796, Node = 325.167, i = 7.752, equinox 2000.0), and an
ephemeris appear on MPEC 2008-S48.

                      (C) Copyright 2008 CBAT
2008 September 24              (8979)            Daniel W. E. Green

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