------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 3080 2015 May 25 18.08UT 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/2015 G2 (MASTER) Vladimir M. Lipunov, Sternberg Astronomical Institute et. al., report the discovery of a comet on 60-s unfiltered survey images taken with the "Mobile Astronomical System of the Telescope-Robots" (MASTER) auto-detection system (double 0.40-m f/2.5 reflector) at the SAAO. Denisenko first noticed the object as being cometary, with a coma diameter of about 1'.5, and elongated toward the west, on R-band images taken by P. Balanutsa et al. 2015 UT R.A. (2000) Decl. Mag. Apr. 7.12551 21 56 37.54 -15 36 56.3 10.7 7.13464 21 56 38.56 -15 37 05.6 10.7 Following appeal from the Minor Planet Center other CCD astrometrists commented. Ernesto Guido and Nick Howes (remotely using an iTelescope 0.50-m f/6.8 astrograph at Siding Spring; 2015 Apr. 8.77 UT) relay 10 stacked 30-s unfiltered exposures show a very bright coma of red mag 13.7 that is nearly 3' in diameter with a tail about 15' long in p.a. 253 deg. H. Sato, Japan, notes 16 stacked 10-s exposures taken with an iTelescope (Siding Spring) on Apr. 8.78 show the object to be strongly condensed with an elongated coma of size 2'.9 and a tail longer than 15' toward p.a. 252 degrees; the w-band magnitude was 10.3, as measured within a circular aperture of radius 87".6. R. Kaufman (Victoria, Australia) reports that four pre-discovery images taken on Mar. 30.802 UT with a Canon 650D camera (+ 200-mm-FL lens) in fairly poor sky conditions shows a bright, diffuse greenish object visible on the bottom edge of the frame in the predicted position of this comet; M. Mattiazzo (Swan Hill, Victoria, Australia) provided astrometric measures for the comet on Kaufman's images, yielding magnitude 11.4-11.9. Visual total-magnitude and coma-diameter estimate: Apr. 8.80 UT, 9.7, 2'.5 (Mattiazzo, 20-cm reflector; moonlight; comet appears moderately condensed and is more condensed but slightly smaller and fainter than comet 88P, which lies 2.5 deg to the northeast) Preliminary parabolic orbital elements by G. V. Williams, and an ephemeris on MPEC 2015-G28. T = 2015 May 23.8022 TT Peri. = 257.4779 Node = 110.0566 2000.0 q = 0.779770 AU Incl. = 147.5512 Date TT R. A. (2000) Decl. Delta r Elong. m1 2015 03 26 21 38 16.5 -13 03 17 1.8877 1.3310 42.3 13.6 2015 04 03 21 49 35.3 -14 35 57 1.6391 1.2236 48.1 12.9 2015 04 09 22 00 12.5 -16 08 37 1.4419 1.1453 52.2 12.4 2015 04 10 22 02 14.7 -16 26 40 1.4083 1.1325 52.8 12.3 2015 04 11 22 04 22.5 -16 45 35 1.3744 1.1197 53.5 12.2 2015 04 17 22 19 46.6 -19 01 20 1.1681 1.0456 57.0 11.5 2015 04 25 22 52 33.6 -23 27 01 0.8909 0.9546 60.1 10.5 2015 05 10 02 08 16.0 -34 57 46 0.4889 0.8244 54.1 8.6 The above ephemeris is all that can be found on G28 and nothing shown on MP Center WWW. Guy M Hurst