Electronic Telegram No. 4286
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/2016 M1 (PANSTARRS)
     Richard Wainscoat and Rob Weryk report the discovery of a comet in four
i-band exposures obtained with the 1.8-m Pan-STARRS1 telescope at Haleakala
on June 22.5 UT (discovery observations tabulated below), in which the comet
appears softer than nearby field stars with a hint of possible asymmetry
extended toward p.a. approximately 150 degrees (perhaps associated with a
faint tail, but only very marginally visible).

     2016 UT             R.A. (2000) Decl.       Mag.
     June 22.46678   18 11 33.54   +69 34 30.4   19.7
          22.47971   18 11 32.41   +69 34 29.1   19.3
          22.49267   18 11 31.23   +69 34 27.8   19.8
          22.50562   18 11 30.09   +69 34 26.7   19.9

After the object was posted on the Minor Planet Center's NEOCP and PCCP
webpages, other CCD astrometrists have also noted the object's cometary
appearance.  G. Hug (Scranton, KS, U.S.A.) writes that his images taken with
a 0.56-m reflector on June 23.13-23.16 UT show the comet to be diffuse.  E.
Bryssinck, Kruibeke, Belgium, notes that seven stacked 180-s images taken on
June 23.3 with a 0.61-m f/6.5 astrograph (+ Bessel I filter) at the Sierra
Remote Observatory near Auberry, CA, USA, shows a starlike nuclear
condensation with a very faint coma 10"-11" in diameter (red magnitude
18.4-1.8).  H. Sato, Tokyo, Japan, relates that twelve stacked 60-s
exposures taken with an iTelescope 0.43-m f/6.8 astrograph (+ luminance
filter) at Nerpio, Spain, on June 23.9 show the comet to be strongly
condensed with an asymmetrical coma 8" in diameter and no tail; the total
w-band magnitude was 18.4 as measured within a circular aperture of radius
5".0.  G. Baj, Varese, Italy, reports that the comet shows a softer aspect
when compared with nearby field stars on exposures taken with a 0.30-m f/8
Ritchey-Chretien reflector at Saltrio.  K. Sarneczky, Konkoly Observatory,
writes that fifteen stacked 90-s unfiltered CCD images taken with the 0.60-m
Schmidt telescope at Piszkesteto, Hungary, on June 24.0 show a round,
condensed head about 8"-10" in diameter with a tail 12" long in p.a. 180 deg.
The R-band magnitude was 18.4 as measured within a circular aperture of
radius 6".0.  Forty-five co-added 30-s exposures taken by P. Bacci with a
0.60-m f/4 reflector at San Marcello Pistoiese, Italy, on June 24.0 show a
diffuse coma 20" in diameter (red mag 17.7-17.9; measurements by Bacci, L.
Tesi, and G. Fagioli).
     The available astrometry (spanning June 22-24), the following preliminary
parabolic orbital elements by G. V. Williams, and an ephemeris appear on MPEC
2016-M18.

     T = 2018 Oct. 26.3330 TT         Peri. = 204.4209
                                      Node  =  81.7478  2000.0
     q = 2.632583 AU                  Incl. =  91.7507


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

                         (C) Copyright 2016 CBAT
2016 June 24                     (CBET 4286)              Daniel W. E. Green