Electronic Telegram No. 4344
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
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Prepared using the Tamkin Foundation Computer Network


COMET C/2017 A3 (ELENIN)
     L. Elenin, Lyubertsy, Russia, reports his discovery of a comet with a
diffuse coma about 14" in size on three CCD images taken with a 0.4-m f/2.4
astrograph of the ISON-SSO Observatory at Siding Spring on Jan. 5 (discovery
observations tabulated below).

     2017 UT             R.A. (2000) Decl.       Mag.   Observer
     Jan.  5.45843    6 52 57.13   -51 07 47.8   17.6   Elenin
           5.46508    6 52 56.21   -51 07 42.9   17.9     "
           5.47172    6 52 55.35   -51 07 37.9   17.6     "

After the presumed comet was posted on the Minor Planet Center's PCCP webpage,
numerous other CCD astrometrists have also commented on the object's cometary
appearance.  Three stacked 60-s images obtained by C. Jacques, E. Pimentel,
and J. Barros with a 0.45-m f/2.9 reflector at the SONEAR Observatory,
Oliveira, Brazil, on Jan. 6.1 UT show a condensed coma 9" in diameter with
red magnitude 18.1-18.5.  Images taken by M. Gedek, M. Zolnowski, M. Kusiak,
and R. Reszelewski on Jan. 6.37, 8.35, 9.3, and 10.3 with a 0.25-m f/3.6
astrograph at the Polonia Observatory at San Pedro de Atacama, Chile, show
the comet to be slightly diffuse, the red magnitude given as 17.7-18.2.
H. Sato, Tokyo, Japan, writes that ten stacked 60-s exposures taken on Jan.
6.5 with a 0.51-m f/6.8 astrograph (+ luminance filter) at Siding Spring
show the comet to be strongly condensed with a coma 12" in diameter and a
hint of tail 20" long toward p.a. 20 degrees; the w-band magnitude was 17.4
as measured within a circular aperture of radius 6".5.  E. Guido,
Castellammare di Stabia, Italy, notes that twenty stacked 120-s unfiltered
exposures obtained remotely with an iTelescope network 0.50-m f/6.8
astrograph at Siding Spring on Jan. 6.54-6.56 show a compact coma nearly 10"
in diameter, elongated toward p.a. 40 deg.  E. Bryssinck, Kruibeke, Belgium,
reports that eleven stacked 60-s exposures taken with an iTelescope 0.51-m
f/4.4 reflector at Siding Spring on Jan. 6.63 show a diffuse circular coma
of diameter 19" with magnitude 17.8 in an aperture of diameter 7".6.  Three
stacked 180-s images taken on Jan. 7.45-7.47 by L. Buzzi, P. Concari, C.
Cremaschini, S. Foglia, G. Galli, and M. Tombelli with an iTelescope 0.15-m
f/7 refractor at Siding Spring reveal a round coma 10" in diameter.  G. Baj
reports that stacked images taken with an iTelescope 0.43-m f/6.8 reflector
at Siding Spring on Jan. 9.5 show a compact coma 13".2 in size with no tail.
     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2017-A75.

     T = 2017 Jan. 20.2058 TT         Peri. = 301.8687
                                      Node  =  96.7337  2000.0
     q = 3.911036 AU                  Incl. =  99.1253


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

                         (C) Copyright 2017 CBAT
2017 January 11                  (CBET 4344)              Daniel W. E. Green