Electronic Telegram No. 4392
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 K1 (PANSTARRS)
     R. J. Wainscoat reports the discovery of an apparent comet on four 45-s
w-band exposures taken with the 1.8-m Pan-STARRS1 telescope at Haleakala
(discovery images tabulated below), the object appearing clearly soft compared
to nearby stars (FWHM 2".0, vs. 1".0 for the stars) with no evidence of a
tail.

     2017 UT             R.A. (2000) Decl.       Mag.
     May  21.40011   15 45 41.77   -28 17 47.7   20.3
          21.41065   15 45 41.17   -28 17 44.8   20.4
          21.42120   15 45 40.58   -28 17 41.6   20.4
          21.43174   15 45 39.97   -28 17 38.6   20.3

A series of nine 60-s w-band follow-up exposures taken by Wainscoat and D.
Woodworth with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on May
23.47 UT show that the comet appears to be extended in each image (FWHM
approximately 1".7, compared approximately 0".9 for nearby stars; measured by
M. Micheli and Wainscoat), the G-band magnitude given as 19.8.  After posting
on the Minor Planet Center's PCCP webpage, H. Sato (Tokyo, Japan) stacked ten
60-s exposures taken on May 22.6 with an iTelescope 0.51-m f/6.8 astrograph
at Siding Spring to find a strongly condensed coma of size 6" x 8" but no
tail; the w-band magnitude was 19.2 as measured within a circular aperture
of radius 4".9.
     The available astrometry, the following very preliminary parabolic
orbital elements by G. V. Williams (from 17 observations spanning May 21-23),
and an ephemeris appear on MPEC 2017-K34.

     T = 2018 Oct. 25.7764 TT         Peri. =  23.8005
                                      Node  = 226.2144  2000.0
     q = 6.574998 AU                  Incl. = 153.1715


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      superseded by text appearing later in the printed IAU Circulars.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 4392)              Daniel W. E. Green