Electronic Telegram No. 4393
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)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2017 K2 (PANSTARRS)
     R. J. Wainscoat reports the discovery of yet another apparent comet at
the edge of four 45-s w-band exposures taken with the 1.8-m Pan-STARRS1
telescope at Haleakala (discovery images tabulated below), the object
having FWHM 1".5, vs. 0".9 for nearby stars.

     2017 UT             R.A. (2000) Decl.       Mag.
     May  21.49169   17 52 21.39   +64 30 27.8   20.8
          21.50472   17 52 20.96   +64 30 29.1   21.1
          21.51771   17 52 20.60   +64 30 29.9   20.8
          21.53069   17 52 20.16   +64 30 31.2   21.0

A series of six 60-s gri-filtered follow-up exposures taken by Wainscoat and
L. Wells with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on May
22.6 UT show that the object is clearly cometary, displaying a coma with a
FWHM of about 1".3 in 0".75 seeing conditions, with the coma elongated to
the west (measured by M. Micheli and Wainscoat); the G-band magnitude was
given as 19.7.  After posting on the Minor Planet Center's PCCP webpage, H.
Sato (Tokyo, Japan) stacked twelve 60-s exposures taken on May 22.45-22.46
with an iTelescope 0.61-m f/6.5 astrograph located at the Sierra Remote
Observatory near Auberry, CA, USA, to find a moderately condensed round
coma 12" in diameter with no tail; the w-band magnitude was 18.9 as measured
within a circular aperture of radius 6".3.
     The available astrometry, the following very preliminary parabolic
orbital elements by G. V. Williams (from 14 observations spanning May 21-24),
and an ephemeris appear on MPEC 2017-K35.

     T = 2027 Jan.  5.2099 TT         Peri. = 183.6446
                                      Node  =   3.4581  2000.0
     q = 9.895879 AU                  Incl. =  94.3954


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2017 CBAT
2017 May 24                      (CBET 4393)              Daniel W. E. Green