Electronic Telegram No. 3605
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/2013 O3 (McNAUGHT)
     R. H. McNaught reports his discovery of a comet with a diffuse coma about
12" in diameter and a faint elongation along p.a. 45-225 deg on images taken
with the 0.5-m Uppsala Schmidt telescope at Siding Spring (discovery
observations tabulated below); deeper follow-up exposures on July 25.4 UT in
good seeing show a strong condensation and a 16" coma involved with stars,
while an exposure taken by McNaught on July 26.4 shows the comet to appear
almost asteroidal with a 12" tail in p.a. 45 deg.  After posting on the Minor
Planet Center's 'NEOCP' webpage, other CCD astrometrists have also commented
on the object's cometary appearance.  H. Sato (Tokyo, Japan) used an
iTelescope 0.32-m f/9 Ritchey-Chretien telescope at Siding Spring on July 25.4
to find a strongly condensed coma 12" in diameter on six stacked 60-s images;
the V-band magnitude as measured within a circular aperture of radius 6".4
was 18.0.  T. Lister reports that eight stacked 85-s images taken by E. J.
Christensen, S. M. Larson, and himself with the 1.0-m f/8 Las Cumbres
Observatory Global Telescope at Sutherland, South Africa, on July 25.9 show
a diffuse coma about 7" across with a lack of central condensation when
compared to stellar point-spread functions.

     2013 UT             R.A. (2000) Decl.       Mag.   Observer
     July 24.64914   18 42 51.09   -67 50 40.3   17.7   McNaught
          24.65638   18 42 48.85   -67 50 31.8   18.3     "
          24.66349   18 42 46.93   -67 50 22.1            "
          24.67071   18 42 44.77   -67 50 11.6   18.5     "
          25.41956   18 39 13.02   -67 33 08.4   17.7     "
          25.42907   18 39 10.38   -67 32 55.4   18.0     "

The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2013-O54.

     T = 2013 Sept.23.3282 TT         Peri. = 341.4916
                                      Node  = 277.0930  2000.0
     q = 3.148990 AU                  Incl. = 102.3896


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 July 27                     (CBET 3605)              Daniel W. E. Green