Electronic Telegram No. 4216
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 X4 (ELENIN)
     Leonid Elenin reports his discovery of a diffuse comet with slight
condensation on three CCD images taken with a 0.4-m f/3 astrograph at the
ISON-NM observatory near Mayhill, NM, USA, on Dec. 3.5 UT (discovery
observations tabulated below); he noted a coma with diameter about 12" and a
15" tail in p.a. 280 deg.

     2015 UT             R.A. (2000) Decl.       Mag.   Observer
     Dec.  3.48520    6 02 39.78   +21 36 39.3   18.2   Elenin
           3.49481    6 02 39.41   +21 36 33.5   17.8     "
           3.50440    6 02 39.05   +21 36 28.0   18.0     "

After the comet was posted on the Minor Planet Center's PCCP webpage, other
CCD astrometrists also noted the object's cometary appearance.  Ten stacked
60-s images obtained by C. Jacques, E. Pimentel, and J. Barros on Dec. 3.7 UT
with an iTelescope 0.51-m f/4.5 reflector at Siding Spring show a condensed
coma 5" in diameter, elongated 8" towards p.a. 145 deg.  H. Sato, Tokyo,
Japan, notes that that eight stacked 60-s exposures taken with an iTelescope
0.51-m f/6.8 astrograph (+ luminance filter) near Mayhill, NM, U.S.A., on
Dec. 3.73 show the comet to be strongly consensed with a coma 15" in diameter
and a short tail 15" long toward p.a. 280 degrees; the w-band magnitude was
16.5 as measured within a circular aperture of radius 8".8.  E. Guido,
Castellammare di Stabia, Italy, writes that twenty stacked 120-s unfiltered
exposures, obtained remotely with an iTelescope 0.32-m f/8 astrograph near
Nerpio, Spain, on Dec. 3.9, show a compact coma nearly 8" in diameter (with
red mag 17.1-17.2), elongated toward p.a. 120 deg.  E. Bryssinck, Kruibeke,
Belgium, relates that four stacked 120-s images obtained on Dec. 4.9 with a
0.4-m f/3.8 astrograph shows a condensed circular coma 12" across.  J.-F.
Soulier obtained unfiltered images with a 0.30-m f/3.8 Newtonian reflector
at Maisoncelles, France, on Dec. 4.90-4.95 that show a 13" coma and a tail
10" long in p.a. 315 deg.  Twenty 2-min exposures taken by D. T. Durig and
S. P. Hearn on Dec. 8.23-8.27 with a 0.3-m f/2.5 Schmidt-Cassegrain reflector
at the Cordell-Lorenz Observatory, Sewanee, TN, USA, show a short tail about
17" long in p.a. 303 deg.

     The available astrometry, the following elliptical orbital elements by
G. V. Williams, and an ephemeris appear on MPEC 2015-X105.

     T = 2015 Nov.  2.6423 TT         Peri. = 176.1520
     e = 0.813430                     Node  = 262.6351  2000.0
     q = 3.393964 AU                  Incl. =  29.4998
       a = 18.191358 AU    n = 0.0127030    P =  77.6 years


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

                         (C) Copyright 2015 CBAT
2015 December 8                  (CBET 4216)              Daniel W. E. Green