Electronic Telegram No. 3476
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 G7 (McNAUGHT)
     R. H. McNaught reports his discovery of a comet on CCD images taken with
the 0.5-m Uppsala Schmidt telescope at Siding Spring (discovery observations
tabulated below), the object described as slightly diffuse (the appearance
he also noted on follow-up images taken the following night through cirrus
clouds).  After it was posted on the Minor Planet Center's NEOCP webpage,
other CCD astrometrists also commented on the object's cometary appearance.
Thirty co-added 30-s images taken by R. Holmes and T. Linder with a 0.41-m
f/11 Ritchey-Chretien reflector at Cerro Tololo on Apr. 14.3 UT show a broad
tail 25".1 long in p.a. 14.2 degrees.  J. G. Ries (McDonald Observatory,
2.1-m reflector + i-band filter) writes that the object shows an extended,
diffuse, symmetrical halo about 7" across on images from Apr. 14.4, while
images from Apr. 15.4 show a diffuse coma of diameter approximately 7" with
a hint of a very slight extension to the northeast; additional images from
Apr. 16.4 seem to indicate more development of a short tail toward the
northeast.  H. Sato (Tokyo, Japan) notes that two stacked 60-s exposures
taken remotely with a 0.51-m f/6.8 astrograph of the iTelescope Observatory
at Siding Spring on Apr. 14.66 show a strongly condensed coma 10" in diameter
with V-band magnitude 18.4 as measured within a circular aperture of radius
6".5; his stacked follow-up exposures on Apr. 15.4 (taken remotely with a
0.43-m f/6.8 astrograph at the iTelescope Observatory near Mayhill, NM, USA)
show a strongly condensed coma 12" in diameter, slightly elongated toward
the north, with a V-band magnitude of 17.9 as measured within a circular
aperture of radius 7".6.  E. Guido (Castellammare di Stabia, Italy) reports
that seventeen stacked 40-s R-band images taken remotely by E. Simpson, N.
Howes, and himself on Apr. 15.44-15.45 with the 2.0-m f/10 "Faulkes Telescope
North" at Haleakala show a compact coma about 6" in diameter.  R. Ligustri
(Udine, Italy) finds a coma of diameter about 20" on six 120-s exposures
taken on Apr. 16.6 with a 0.50-m f/4.5 reflector of the iTelescope Observatory
at Siding Spring.

     2013 UT             R.A. (2000) Decl.       Mag.   Observer
     Apr. 13.64649   15 35 39.41   -14 22 45.2   18.1   McNaught
          13.65731   15 35 38.77   -14 22 47.1   17.9     "
          13.68967   15 35 36.87   -14 22 53.6   17.9     "
          13.79403   15 35 30.80   -14 23 14.5            "
          13.79659   15 35 30.63   -14 23 14.8            "

The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2013-H10.

     T = 2014 Apr. 20.3498 TT         Peri. = 225.3215
                                      Node  =  48.4064  2000.0
     q = 4.381937 AU                  Incl. = 104.1123


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

                         (C) Copyright 2013 CBAT
2013 April 16                    (CBET 3476)              Daniel W. E. Green