Electronic Telegram No. 3261 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; 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/2012 T5 (BRESSI) [Editor's note: this text replaces that on CBET 3258 (p.a. error)] T. H. Bressi reports his discovery of a diffuse comet with an apparent faint tail about 9" long in p.a. 260 degrees on CCD mosaic images taken with the Spacewatch 0.9-m f/3 reflector at Kitt Peak (discovery observations tabulated below); follow-up observations by Bressi with the Spacewatch 1.8-m f/2.7 reflector on Oct. 16.3 UT show the comet to be diffuse with a broad tail extending about 10" in p.a. about 270 deg. After posting on the Minor Planet Center's NEOCP webpage, other CCD astrometrists have also reported on the object's cometary appearance. Images taken by P. Ruiz (1.0-m f/4.4 reflector at the European Spage Agency's Optical Ground Station, Tenerife; Oct. 16.0; measured by A. Kn\"ofel, D. Koschny, and M. Busch) show the small tail. William H. Ryan (Magdalena Ridge Observatory, 2.4-m f/8.9 reflector; Oct. 16.3) notes a distinct coma and a tail in p.a. about 270 deg in R-band images. G. Hug (Scranton, KS, U.S.A.; 0.56-m reflector; Oct. 16.3) found a short, broad tail in p.a. about 290 deg. Fifteen stacked 60-s exposures taken by R. Holmes (Ashmore, IL, USA; 0.61-m f/4 astrograph; measured by L. Buzzi, H. Devore, S. Foglia, and T. Vorobjov; Oct. 16.4) show a coma 15" x 10" in size, elongated in p.a. 280 deg, and a wide tail 45" long in p.a. 275 degrees. E. Bryssinck (Kruibeke, Belgium; 0.4-m f/3.8 astrograph; Oct. 16.9) writes that nine stacked, unfiltered images reveal a coma of size 12" x 16", elongated toward p.a. about 285 deg, with a very faint tail extending for approximately 18" in p.a. 273 degrees. L. Buzzi (Varese, Italy; 0.38-m f/6.8 reflector; Oct. 17.0) reports that a stack of images totalling 39 minutes of exposure time in good seeing (but with passing high clouds) shows a diffuse coma 10" wide, with a fan-shaped tail 15" long in p.a. about 275 deg. Images obtained by G. Masi and F. Nocentini (Ceccano, Italy; 0.36-m f/8.7 reflector; measured by G. Masi and U. Masi; Oct. 17.0) show a coma at least 10" in size. R. Ligustri (Udine, Italy; remotely using a 0.25-m f/3.3 reflector at the RAS Observatory near Mayhill, NM, U.S.A.; Oct. 17.5) finds that ten 120-s stacked images show a diffuse coma and a 30" tail toward p.a. 260 deg. H. Sato (Tokyo, Japan; remotely using a 0.51-m f/6.8 astrograph at the RAS Observatory near Mayhill, NM, U.S.A.; Oct. 17.5) finds a moderately condensed coma of diameter 23" (with V-band magnitude 17.7 measured within a circular aperture of radius 11".5) and a 30" tail toward p.a. 280 degrees. Seven stacked 120-s R-band images taken remotely by E. Guido, G. Sostero, and N. Howes with a 0.43-m f/6.8 astrograph at the RAS Observatory (ITelescope network) near Mayhill, NM, U.S.A. on Oct. 18.33 shows a compact coma about 5" in diameter (mag 17.9-18.2) and a tail nearly 12" long in p.a. 270 deg. 2012 UT R.A. (2000) Decl. Mag. Observer Oct. 14.41919 4 17 29.19 +21 57 27.1 18.6 Bressi 14.43695 4 17 28.43 +21 57 15.7 18.4 " 14.45466 4 17 27.47 +21 57 02.1 18.6 " The available astrometry, the following preliminary parabolic orbital elements by Gareth V. Williams, and an ephemeris appear on MPEC 2012-U38. T = 2013 Feb. 23.5584 TT Peri. = 318.2738 Node = 230.5578 2000.0 q = 0.319891 AU Incl. = 71.8724 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2012 CBAT 2012 October 18 (CBET 3261) Daniel W. E. Green