Electronic Telegram No. 4141
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/2015 R1 (PANSTARRS)
     Eva Lilly and Richard Wainscoat report the discovery of a comet in three
i-band exposures taken with the 1.8-m Pan-STARRS1 telescope at Haleakala on
Sept. 8.6 UT (discovery observations tabulated below), noting evidence of a
short diffuse tail extending for approximately 2" towards position angle
approximately 270 degrees.

     2015 UT             R.A. (2000) Decl.       Mag.
     Sept. 8.57045    2 57 31.38   - 0 28 23.0   19.0
           8.58433    2 57 31.42   - 0 28 18.2   19.0
           8.59818    2 57 31.46   - 0 28 13.3   19.1

M. Micheli reports that CCD images taken by R. J. Wainscoat and P. Forshay
with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on Sept. 9.55 UT
confirm the object to be clearly cometary with a tail about 75" long in p.a.
240 deg.  After the object was posted on the Minor Planet Center's PCCP
webpage, other CCD astrometrists have commented on the cometary appearance.
Twenty 180-s mages taken by A. Maury and J.-F. Soulier with a 0.4-m f/8
Ritchey-Chretien reflector at San Pedro de Atacama, Chile, on Sept. 9.3
show a 14" coma with a 20"-long tail in p.a. 245 deg.  E. Bryssinck,
Kruibeke, Belgium, reports that fifteen stacked 120-s exposures taken on
Sept. 10.1 with a 0.4-m f/3.8 reflector show a condensed coma 13" in size
that is elongated toward the southsest (p.a. 240 deg)) with a hint of a tail
19" long.
     The available astrometry, the following preliminary elliptical orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2015-R39.

     T = 2015 June 14.3291 TT         Peri. = 292.1871
     e = 0.869961                     Node  =  50.6086  2000.0
     q = 2.120504 AU                  Incl. =  21.8984
       a = 16.306738 AU    n = 0.0149676    P =  65.8 years


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 September 12                (CBET 4141)              Daniel W. E. Green