Electronic Telegram No. 4331
Central Bureau for Astronomical Telegrams
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Prepared using the Tamkin Foundation Computer Network


COMET C/2016 T3 (PANSTARRS)
     R. Weryk and E. Lilly, Institute for Astronomy, University of Hawaii,
report the discovery of another apparent comet in three i-band exposures
obtained with the 1.8-m Pan-STARRS1 telescope at Haleakala on Oct. 10
(discovery observations tabulated below).  The FWHM of nearby star images is
0".9, while the apparent comet has an FWHM of about 1".3; the object looks
asymmetric, likely due to a short tail extending for about 4" towards p.a.
300 degrees.

     2016 UT             R.A. (2000) Decl.       Mag.
     Oct. 10.38004    1 40 59.46   +37 39 00.7   20.1
          10.39169    1 40 59.08   +37 38 59.4   20.1
          10.40337    1 40 58.67   +37 38 58.2   20.1

M. Micheli, R. Weryk, and R. Wainscoat report that they obtained follow-up
images via three 60-second gri-filtered exposures using the 3.6-m Canada-
France-Hawaii Telescope at Mauna Kea on Oct. 11.6 UT (queue observer C.
Wipper), showing that the object is clearly cometary and displays an obvious
tail at least 10" long toward a p.a. about 240 deg; the core of the coma has
a FWHM of about 1".2, compared to 0".8 for nearby-star images.  After the
comet was posted on the Minor Planet Center's NEOCP and PCCP webpages, other
CCD astrometrists have also commented on the cometary appearance.  H. Sato,
Tokyo, Japan, writes that stacked sixteen 60-s exposures obtained on Oct. 12.1
UT with an iTelescope 0.43-m f/6.8 astrograph (+ luminance filter) at Nerpio,
Spain, show a strongly condensed coma 8" in diameter and no tail; the w-band
magnitude was 19.0 as measured within a circular aperture of radius 5".0.
Sato also notes that stacked ten 60-s exposures obtained on Oct. 12.4 with an
iTelescope 0.51-m f/6.8 astrograph (+ luminance filter) near Mayhill, NM, USA,
show the comet to be moderately condensed with a coma 10" in diameter and
agian no tail; the w-band magnitude was 18.9 as measured within a circular
aperture of radius 6".5.  L. Buzzi, Varese, Italy, obtained images of the
comet with a 0.60-m f/4.6 reflector on Oct. 16.0, which show a strong central
condensation with a tail at least 8" long in p.a. 240 degrees, even though the
full moon was just 33 deg away; the tail was confirmed with two separate
stacks employing different images.
     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams (from 31 observations spanning Oct. 10-18), and an
ephemeris appear on MPEC 2016-U10.

     T = 2017 Sept. 6.7452 TT         Peri. = 195.5152
                                      Node  = 271.5210  2000.0
     q = 2.622900 AU                  Incl. =  22.7521


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

                         (C) Copyright 2016 CBAT
2016 October 18                  (CBET 4331)              Daniel W. E. Green