Electronic Telegram No. 4138
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/2015 Q1 (SCOTTI)
     J. V. Scotti, Lunar and Planetary Laboratory, reports his discovery of
a diffuse comet with a short tail extending toward the west on CCD mosaic
images obtained with the Spacewatch 0.9-m f/3 reflector at Kitt Peak
(discovery astrometry tabulated below).  Scotti adds that the comet shows a
8" coma with a tail about 0'.23 long in p.a. 272 degrees.  His follow-up
observations with the Spacewatch 1.8-m f/2.7 reflector on Aug. 19.44-19.46
UT show a 8".4 coma and tail extending 1'.25 in p.a. 271 degrees in stacked
exposures.

     2015 UT             R.A. (2000) Decl.       Mag.   Observer
     Aug. 18.45786    4 14 32.11   +17 57 15.2   18.9   Scotti
          18.47195    4 14 34.15   +17 57 08.6   18.9     "
          18.48605    4 14 36.15   +17 57 01.9   18.9     "
          19.44241    4 16 55.43   +17 49 32.1   18.3     "
          19.44993    4 16 56.51   +17 49 28.5   18.1     "
          19.45743    4 16 57.58   +17 49 24.9            "

After the comet was posted on the Minor Planet Center's PCCP webpage, other
CCD astrometrists have commented on the cometary appearance.  H. Sato, Tokyo,
Japan, writes that sixteen stacked 60-s exposures taken with an iTelescope
0.51-m f/6.8 astrograph at Siding Spring on Aug. 18.8 UT show the comet to be
strongly condensed with a coma 10" in diameter and a tail 60" long toward
p.a. 275 degrees; the w-band magnitude was 18.0 as measured within a circular
aperture of radius 6".6.  J.-F. Soulier obtained images with a 0.30-m f/3.8
Newtonian reflector at Maisoncelles, France, on Aug. 19.05-19.11 that show a
15" coma and a tail 36" long in p.a. 260 deg; A. Maury and Soulier also
obtained images with a 0.4-m f/8 Ritchey-Chretien reflector at San Pedro de
Atacama, Chile, on Aug. 19.33-19.36 that show a 12" coma and a tail 30" long
in p.a. 255 deg.  W. H. Ryan, Magdalena Ridge Observatory, found the comet
to show a distinct tail toward p.a. about 270 deg on R-band images taken
with the 2.4-m f/8.9 reflector on Aug. 19.44-19.46.
     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2015-Q25.

     T = 2015 Oct.  2.0871 TT         Peri. = 210.3958
                                      Node  = 208.0539  2000.0
     q = 1.903668 AU                  Incl. =  24.7569


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 August 20                   (CBET 4138)              Daniel W. E. Green