Electronic Telegram No. 3238
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 S1 (ISON)
     Vitali Nevski (Vitebsk, Belarus) and Artyom Novichonok (Kondopoga, Russia)
report their discovery of a diffuse comet with an 8" coma on four 100-s CCD
exposures obtained on Sept. 21.06 UT with a 0.4-m f/3 Santel reflector of
the International Scientific Optical Network (ISON) near Kislovodsk, Russia
(discovery observations tabulated below); Nevski and Novichonok first reported
the object to the Minor Planet Center with no mention of cometary appearance,
and it was posted on the MPC's NEOCP webpage as an apparently asteroidal
object (their report to the Central Bureau of cometary appearance arrived
nearly a day after NEOCP posting).  Follow-up observations obtained with
a 1.5-m f/8 reflector at the Majdanak observatory in Uzbekistan by O. Burhonov
(measured by Novichonok and Nevski) on Sept. 21.99 show an obvious elongation
in p.a. 305 deg with a coma of size 9" x 11" and total mag about 17.1.  After
the object was posted on the MPC's NEOCP webpage, other CCD astrometrists
commented on the object's cometary appearance (including one or two such
reports received before Nevski's e-mail to the Central Bureau noting cometary
appearance).  W. H. Ryan (Magdalena Ridge Observatory, 2.4-m f/8.9 reflector)
noted an elongated nuclear condensation and a faint tail in p.a. about 280 deg
on R-band images taken on Sept. 21.4; follow-up images taken by W. H. Ryan and
E. V. Ryan on Sept. 22.4 and 23.4 show an elongated nuclear condensation and a
distinct tail in p.a. about 280 deg.  H. Sato (Tokyo, Japan; remotely using a
0.51-m f/6.8 astrograph at the RAS Observatory near Mayhill, NM, U.S.A., on
Sept. 22.5) found a disk-like object 10" in diameter.  E. Guido, G. Sostero,
and N. Howes stacked twenty-four 120-s unfiltered exposures obtained remotely
on Sept. 22.5 with a 0.25-m f/3.4 reflector at the RAS Observatory near
Mayhill to find a slightly diffuse object that was slightly larger than nearby
field stars of similar brightness.

     2012 UT             R.A. (2000) Decl.       Mag.   Observer
     Sept.21.05253    8 12 43.09   +27 50 22.1   18.8   Nevski
          21.05974    8 12 43.23   +27 50 21.7   19.0     "
          21.06577    8 12 43.40   +27 50 21.3   18.9     "
          21.07059    8 12 43.46   +27 50 21.6   19.1     "

The available astrometry (including prediscovery observations identified by
G. V. Williams in MPC data from the Mount Lemmon Survey on 2011 Dec. 28 and
from the 1.8-m f/4 Pan-STARRS reflector on 2012 Jan. 28), the following
nearly parabolic (e = 0.999999964) orbital elements by Williams, and an
ephemeris appear on MPEC 2012-S63.

                    Epoch = 2013 Dec. 14.0 TT
     T = 2013 Nov. 28.8704 TT         Peri. = 345.5614
     e = 1.000000                     Node  = 295.6595  2000.0
     q = 0.012453 AU                  Incl. =  62.3643


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

                         (C) Copyright 2012 CBAT
2012 September 24                (CBET 3238)              Daniel W. E. Green