Electronic Telegram No. 5740 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 P/2026 R1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on Sept. 5 (discovery observations tabulated below). Four stacked 45-s w-band survey images taken in 1".2-1".6 seeing show a very condensed head of size 1".6 (full-width-at-half-maximum) with a broad tail 8" long spanning p.a. 250-275 degrees. 2026 UT R.A. (2000) Decl. Mag. Sept. 5.58539 3 04 47.58 -31 03 40.3 20.6 5.59522 3 04 47.81 -31 03 45.7 20.5 5.60566 3 04 48.06 -31 03 51.4 20.7 5.61548 3 04 48.27 -31 03 56.8 20.5 Four additional stacked 45-s Pan-STARRS1 w-band survey images taken on Sept. 16.55-16.58 UT in 1".2-1".3 seeing show a very condensed head of size 1".4 (FWHM) with a broad tail approximately 15" long spanning p.a. 250-290 degrees. Three stacked 60-s gri-band exposures taken on Sept. 6.57 by Weryk and R. Wainscoat with the 3.6-m Canada-France-Hawaii Telescope on Mauna Kea in 0".8-0".9 seeing (queue observer C. Wipper; queue coordinator V. Khatu) show a condensed head of size 1".3 (FWHM) and mag 20.3-20.4 with a broad tail > 10" long spanning p.a. 245-305 degrees. After the comet was posted to the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) obtained twelve stacked 60-s CCD exposures on Sept. 6.74 UT with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, that show a strongly condensed coma 8" in diameter and a 15"-long tail spanning p.a. 255-290 degrees; the magnitude was 19.9 as measured within a circular aperture of radius 4".9. The available astrometry appears on MPEC 2026-S39. The following preliminary elliptical orbital elements by S. Nakano (Central Bureau) are from 26 observations spanning 2026 Sept. 5-16 (mean residual 0".4). There are no close approaches to major planets. T = 2026 June 27.16326 TT Peri. = 237.48747 e = 0.4291960 Node = 93.75143 2000.0 q = 1.7974921 AU Incl. = 27.23501 a = 3.1490533 AU n = 0.17637380 P = 5.59 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 16.5 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2026 08 28 02 59.42 -29 45.1 1.223 1.870 113.4 29.7 19.7 2026 09 07 03 05.36 -31 16.2 1.200 1.894 117.9 28.0 19.7 2026 09 17 03 06.73 -32 38.6 1.185 1.921 122.4 26.2 19.7 2026 09 27 03 03.54 -33 40.7 1.178 1.951 126.8 24.3 19.8 2026 10 07 02 56.28 -34 10.5 1.183 1.983 130.4 22.6 19.8 2026 10 17 02 46.02 -33 56.7 1.202 2.018 133.0 21.2 19.9 2026 10 27 02 34.41 -32 52.5 1.236 2.054 134.0 20.4 20.1 2026 11 06 02 23.21 -30 59.0 1.287 2.093 133.0 20.3 20.3 2026 11 16 02 13.88 -28 23.1 1.357 2.132 130.1 20.8 20.5 2026 11 26 02 07.38 -25 16.5 1.444 2.174 125.7 21.6 20.7 2026 12 06 02 03.98 -21 51.7 1.549 2.216 120.3 22.6 20.9 2026 12 16 02 03.62 -18 19.4 1.669 2.259 114.2 23.4 21.2 2026 12 26 02 05.99 -14 47.5 1.803 2.303 107.8 24.0 21.4 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 September 18 (CBET 5740) Daniel W. E. Green