------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 3072 2015 Apr 10 20.09UT 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) Denis V. Denisenko, Sternberg Astronomical Institute, reports the discovery of a comet with a coma diameter of about 1'.5, and elongated toward the west, on R-band images taken by P. Balanutsa et al. with the MASTER (Mobile Astronomical System of the Telescope-Robots) 0.4-m f/2.5 reflector at the South African Astronomical Observatory (discovery observations tabulated below). 2015 UT R.A. (2000) Decl. Mag. Apr. 7.12551 21 56 37.54 -15 36 56.3 10.7 7.13007 21 56 38.03 -15 37 00.7 10.6 7.13464 21 56 38.56 -15 37 05.6 10.7 CCD astrometrists have commented on the object's cometary appearance. Ernesto Guido et. al. remotely using an iTelescope 0.50-m f/6.8 astrograph at Siding Spring; Apr. 8.77 UT) write that ten 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, Tokyo, Japan, notes that sixteen stacked 10-s exposures taken with an iTelescope 0.51-m f/6.8 astrograph (+ luminance filter) at 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. C. Jacques (Belo Horizonte, MG, Brazil) reports that six stacked CCD images obtained on Apr. 10.34 by E. Pimentel, J. Barros, and himself with a 0.28-m f/2.2 astrograph at the SONEAR Observatory, Oliveira, show a coma 2'35" in diameter with a strong central condensation and a tail 2'40" long in p.a. 252 deg. R. Kaufman (Bright, Victoria, Australia) reports four pre-discovery images taken of Mar. 30.80UT with a Canon 650D camera (+ 200-mm-f.l. lens). Visual total-magnitude and coma-diameter estimates: 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); 9.34, 10.0, 1'.5 (A. Amorim, Florianopolis, Brazil, 0.18-m reflector; moonlight); 9.48, 10.2:, 1'.5 (A. Hale, Cloudcroft, NM, USA, 0.41-m reflector; low altitude; bright moonlight, twilight). 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 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 M.P.E.C. 2015-G28