Electronic Telegram No. 3245
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/2012 S4 (PANSTARRS)
     Bryce Bolin, Larry Denneau, Richard Wainscoat, Rob Jedicke, Peter
Veres, and Marco Micheli report the discovery of a comet that appears
non-stellar in each of the two i-band and two r-band discovery exposures that
were obtained by the Pan-STARRS1 telescope (discovery observations tabulated
below); the full-width-at-half-maximum of star images in each exposure was
approximately 1".25, while the comet has a FWHM of approximately 2".  After
posting on the Minor Planet Center's NEOCP webpage, other CCD astrometrists
have commented on the object's cometary appearance.  P. Birtwhistle (Great
Shefford, Berkshire, England; 0.40-m f/6 Schmidt-Cassegrain reflector) found
the comet to appear distinctly diffuse with a 10" coma that is only moderately
condensed, though elongated slightly north-south with no tail visible, on
images from Sept. 29.1 UT; his follow-up exposures on Sept. 29.9 also show
a diffuse 10" coma with no tail.  Stacked images taken by R. Holmes (Ashmore,
IL, USA; 0.81-m f/4 astrograph; measured by T. Vorobjov, L. Buzzi, and S.
Foglia) on Sept. 30.2 show a 10' coma.  Images taken by J. D. Armstrong and M.
Micheli with 2.0-m f/10 "Faulkes Telescope North" at Haleakala on Sept. 30.3
show a definitely cometary appearance (FWHM of coma about 2".8 in 1".1 seeing,
but with no obvious tail in 800 s of total exposure time).  H. Sato (Tokyo,
Japan; images taken remotely with a 0.43-m f/6.8 astrograph at the RAS
Observatory near Mayhill, NM, USA) writes that twelve stacked 60-s images
taken on Sept. 30.4 show a coma that was strongly condensed and 12" in
diameter.  Images taken by G. Masi and F. Nocentini (Ceccano, Italy; 0.43-m
f/6.8 reflector; measured by G. Masi and U. Masi) on Sept. 30.9 show a 10"
coma.

     2012 UT             R.A. (2000) Decl.       Mag.
     Sept.28.41495    0 54 03.06   +60 18 16.0   19.3
          28.42816    0 54 01.35   +60 18 09.4   19.3
          28.44101    0 53 59.71   +60 18 02.9   19.2
          28.45291    0 53 58.18   +60 17 56.6   19.3

The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2012-T04.

     T = 2013 June 29.5635 TT         Peri. = 163.9611
                                      Node  = 173.1503  2000.0
     q = 4.337831 AU                  Incl. = 126.5168


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

                         (C) Copyright 2012 CBAT
2012 October 2                   (CBET 3245)              Daniel W. E. Green