Electronic Telegram No. 2822
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2011 S1 (GIBBS)
     A. R. Gibbs reports the discovery of a comet on CCD images obtained
by Gibbs and S. F. Tornero with the Mt. Lemmon 1.5-m reflector (discovery
observations tabulated below), when four co-added 30-s frames taken in
good seeing show a stellar nuclear condensation with no coma but a broad
tail 7" long in p.a. 260 deg; four co-added 80-s follow-up images taken in
good seeing by Gibbs on Sept. 19.4 UT show a compact coma of size 3" x 5",
elongated in p.a. 260 deg (with a very faint "haze" in the same p.a.).
Following posting on the Minor Planet Center's NEOCP webpage, other CCD
astrometrists have also noticed cometary appearance.  Images taken by P.
Miller, P. Roche, A. Tripp, R. Miles, R. Holmes, L. Buzzi, and S. Foglia
with the a 2.0-m f/10 Ritchey-Chretien reflector at Haleakala ("Faulkes
Telescope North") on Sept. 20.5 show a soft, round coma of diameter 8".
G. Sostero, N. Howes, and E. Guido write that three stacked 120-s R-band
exposures taken remotely on Sept. 21.6 with a 2.0-m f/10 Ritchey-Chretien
reflector at Siding Spring ("Faulkes Telescope South") reveal a diffuse
coma nearly 6" in diameter.

     2011 UT             R.A. (2000) Decl.       Mag.   Observer
     Sept.18.27457   23 26 06.43   - 1 12 22.3   21.2   Gibbs
          18.29549   23 26 05.92   - 1 12 24.3   20.3     "
          19.36174   23 25 44.50   - 1 14 50.9   20.5     "
          19.38629   23 25 43.93   - 1 14 55.3   20.0     "

The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2011-S28.

     T = 2013 Jan. 16.537 TT          Peri. = 174.646
                                      Node  = 229.922   2000.0
     q = 4.98785 AU                   Incl. =   2.233


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2011 CBAT
2011 September 21                (CBET 2822)              Daniel W. E. Green