[IAUC] IAUC 9197: C/2011 C1 [25139-2011/04-R1]

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                                                  Circular No. 9197
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
New postal address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
CBATIAU en EPS.HARVARD.EDU           ISSN 0081-0304
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Prepared using the Tamkin Foundation Computer Network


COMET C/2011 C1 (McNAUGHT)
     R. H. McNaught reports his discovery of a strongly condensed
comet with a 12" coma and a very diffuse tail 0'.3 to the west on
CCD images taken with the 0.5-m Uppsala Schmidt telescope at Siding
Spring (discovery observation tabulated below); his follow-up
images on Feb. 11.77 UT show a strongly condensed circular coma of
diameter 0'.6 and total mag 16.4, while his images taken on Feb.
12.77 show the object to be less strongly condensed than previously
with a 0'.4 coma/tail of total mag 16.7 on the westward side of the
condensation.  After posting on the Minor Planet Center's 'NEOCP'
webpage, numerous other CCD astrometrists have also commented on
the object's cometary appearance.  The following physical data have
been reported to the Central Bureau:  Feb. 11.24, 15" weakly
condensed coma (total mag 16.8), 1' fan-like tail in p.a. 280 deg
(H. Sato, Tokyo, Japan; remotely using a 0.43-m reflector at the
RAS Observatory, Nerpio, Spain); Feb. 11.45 and 12.48, about 25"
round coma (S. Foglia, with S. Baroni, L. Buzzi, P. Concari, G.
Galli, and M. Tombelli, remotely using a 0.18-m refractor at the
Tzec Maun Observatory, Cloudcroft, NM, U.S.A.; eight stacked 60-s
exposures); Feb. 11.49, 1'.7 round, diffuse coma of total mag 14.4
(A. Novichonok, Kondopoga, Russia; and T. Kryachko and S. Korotkiy,
Moscow; remotely with a 0.21-m refractor at Tzec Maun Observatory;
three stacked 180-s exposures; no tail; nuclear condensation of mag
16.5); Feb. 11.49, diffuse, faint coma of size about 25" (G. Hug,
Scranton, KS, U.S.A., 0.56-m reflector); Feb. 11.5, very distinct
coma (W. H. Ryan and E. V. Ryan, 2.4-m reflector, Magdalena Ridge
Observatory, R-band images); Feb. 11.5, about 20" diffuse coma and
broad tail about 30" long in p.a. 275 deg (E. Guido and G. Sostero,
0.25-m reflector, remotely using a 0.25-m refractor of the Global
Rent-a-Scope Network near Mayhill, NM, U.S.A.; sixteen stacked,
unfiltered, 120-s exposures); Feb. 11.53, diffuse outer coma of
size 28" x 24", and 5" x 3".5 inner coma elongated in p.a. 90 deg/
270 deg (A. R. Gibbs, Mt. Lemmon 1.5-m reflector; four co-added
60-s exposures); Feb. 12.2, 15" coma with strong central
condensation and a faint, broad tail in p.a. about 280 deg (L.
Buzzi, Varese, Italy, 0.38-m reflector; 29 stacked 30-s exposures);
Feb. 12.5, about 30" faint coma elongated in p.a. 290 deg (R.
Ligustri, remotely using a 0.50-m reflector at the RAS Observatory
near Mayhill); Feb. 12.5, about 25" coma, elongated in p.a. 270 deg
(J. E. McGaha, Tucson, AZ, 0.36-m Schmidt-Cassegrain reflector;
seven stacked 60-s exposures); Feb. 12.8, 0'.4 coma (K. Kadota,
Ageo, Japan, 0.25-m reflector; total mag 16.6).

     2011 UT             R.A. (2000) Decl.       Mag.   Observer
     Feb. 10.71510   15 59 24.02   -18 06 14.7   17.0   McNaught

                      (C) Copyright 2011 CBAT
2011 February 12               (9197)            Daniel W. E. Green