------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2858 2012 Sep 25 14.15UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- COMET C/2012 S1 (ISON) Vitali Nevski (Vitebsk, Belarus) and Artyom Novichonok (Kondopoga, Russia) report on CBET 3238 their discovery of a diffuse comet with an 8" coma on CCD exposures of 2012 Sept. 21.06 UT with a 0.4-m f/3 reflector of the International Scientific Optical Network (ISON) near Kislovodsk, Russia: 2012 UT R.A. (2000) Decl. Mag. Observer Sept.21.05253 8 12 43.09 +27 50 22.1 18.8 Nevski 21.05974 8 12 43.23 +27 50 21.7 19.0 " 21.06577 8 12 43.40 +27 50 21.3 18.9 " 21.07059 8 12 43.46 +27 50 21.6 19.1 " They initially reported the object to the MPC with no mention of cometary appearance, and it was posted on the NEOCP webpage as an apparent asteroid. Follow-up observations by O. Burhonov at Majdanak observatory on Sept. 21.99 show an obvious elongation in p.a. 305 deg with a coma of size 9" x 11" and total mag about 17.1. After posting on the NEOCP other CCD astrometrists commented on the object's cometary appearance including W. H. Ryan (Magdalena Ridge Observatory, 2.4-m f/8.9 reflector) noted an elongated nuclear condensation and a faint tail in p.a. about 280 deg on R-band images taken on Sept. 21.4. Gareth Williams reports on M.P.E.C. 2012-S63: Orbital elements (using some pre-discovery measures): Epoch 2013 Dec. 14.0 TT = JDT 2456640.5 T 2013 Nov. 28.87041 TT MPC q 0.0124527 (2000.0) P Q z +0.0000029 Peri. 345.56137 +0.31509387 +0.51287068 +/-0.0002325 Node 295.65952 -0.75896421 -0.36901142 e 1.0000000 Incl. 62.36426 -0.56981504 +0.77510918 >From 54 observations 2011 Dec. 28-2012 Sept. 23, mean residual 0".3. Ephemeris: C/2012 S1 (ISON) Date TT R. A. (2000) Decl. Delta r Elong. m1 2012 08 25 08 00 13.1 +28 10 21 7.3403 6.5526 36.3 18.5 2012 09 09 08 07 34.4 +27 57 06 7.0264 6.4094 48.9 18.3 2012 09 17 08 11 04.8 +27 52 11 6.8423 6.3324 55.8 18.2 2012 09 23 08 13 27.9 +27 49 41 6.6975 6.2743 61.1 18.1 2012 09 24 08 13 50.4 +27 49 23 6.6729 6.2646 62.0 18.1 2012 09 25 08 14 12.4 +27 49 07 6.6482 6.2548 62.9 18.1 2012 10 01 08 16 15.6 +27 48 12 6.4972 6.1964 68.2 18.0 2012 10 09 08 18 32.9 +27 49 04 6.2901 6.1180 75.6 17.9 2012 10 24 08 21 10.2 +27 58 07 5.8902 5.9697 89.8 17.6 Ernesto Guido e-mails an image of the new comet of Sept 22 and notes to TAHQ: Comet C/2012 S1 (ISON) will get to within 0.012AU of the Sun at the end of November 2013 and then to ~0.4AU from Earth at the beginning of January 2014! According to its orbit, this comet might become a naked-eye object in the period November 2013 - January 2014. (Accurate magnitude predictions are not feasible at this early stage after discovery: editor) Guy M Hurst