Electronic Telegram No. 5721 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 C/2026 O1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in four 45-s w-band survey images obtained in 1".7-2".0 seeing with the Pan-STARRS2 1.8-m Ritchey- Chretien reflector at Haleakala (discovery observations tabulated below). Stacked images show the head to have a fuzzy/marginal appearance with size 2".4 (full-width-at-half-maximum), but no obvious coma and no tail. 2026 UT R.A. (2000) Decl. Mag. July 19.58495 0 13 22.89 -10 32 56.8 20.3 19.59203 0 13 22.72 -10 33 01.0 20.3 19.59909 0 13 22.54 -10 33 05.0 20.3 19.60617 0 13 22.37 -10 33 09.2 20.3 Three stacked 60-s gri-band follow-up images obtained by Weryk and R. Wainscoat with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on July 20.6 UT in 0".6-0".7 seeing show a very condensed head of size 1".0 (FWHM) and no tail. Three additional stacked 90-s CFHT follow-up exosures taken in 0".8 seeing on July 21.6 (queue observer J. Nagasako; queue coordinator J. Ou) show a hint of a very faint tail extending perhaps 10" toward the west; the very condensed head showed a size of 1".1-1".2 (FWHM). Twelve stacked 60-s CCD exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, on July 19.8 UT show a strongly condensed head with an outer coma 10" in diameter and no tail; the magnitude was 19.4 as measured within a circular aperture of radius 6".5. The available astrometry appears on MPEC 2026-P49. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 54 observations spanning 2026 July 19-Aug. 7 (mean residual 0".3). The comet passed 2.00 AU from Saturn on 2025 June 1 UT. T = 2027 July 18.53773 TT Peri. = 304.47494 Node = 177.91669 2000.0 q = 1.4984840 AU Incl. = 137.24013 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 11.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2026 07 19 00 13.61 -10 27.3 4.039 4.584 116.6 11.4 19.8 2026 07 29 00 08.82 -12 11.6 3.800 4.491 127.5 10.3 19.6 2026 08 08 00 01.92 -14 14.0 3.584 4.397 138.6 8.8 19.4 2026 08 18 23 52.75 -16 32.8 3.398 4.303 149.7 6.8 19.2 2026 08 28 23 41.29 -19 03.4 3.247 4.208 159.4 4.8 19.0 2026 09 07 23 27.77 -21 38.9 3.137 4.112 163.3 4.0 18.9 2026 09 17 23 12.67 -24 10.3 3.069 4.017 157.5 5.5 18.8 2026 09 27 22 56.78 -26 28.3 3.045 3.920 146.6 8.1 18.7 2026 10 07 22 41.03 -28 25.9 3.058 3.824 134.3 10.8 18.6 2026 10 17 22 26.38 -29 59.4 3.104 3.727 121.8 13.1 18.5 2026 10 27 22 13.60 -31 08.9 3.173 3.629 109.6 15.0 18.5 2026 11 06 22 03.16 -31 57.2 3.258 3.531 97.8 16.2 18.4 2026 11 16 21 55.28 -32 28.2 3.348 3.433 86.5 16.7 18.4 2026 11 26 21 49.94 -32 46.4 3.436 3.335 75.8 16.7 18.4 2026 12 06 21 46.96 -32 55.6 3.516 3.236 65.6 16.1 18.3 2026 12 16 21 46.11 -32 58.9 3.580 3.137 56.0 15.1 18.2 2026 12 26 21 47.11 -32 59.1 3.624 3.038 46.9 13.7 18.2 2027 03 16 22 36.99 -35 18.4 2.979 2.257 36.4 15.2 16.7 2027 03 26 22 46.91 -36 34.1 2.771 2.165 43.8 18.6 16.4 2027 04 05 22 57.82 -38 20.0 2.542 2.075 51.7 22.2 16.1 2027 04 15 23 10.15 -40 47.6 2.294 1.988 59.8 25.8 15.7 2027 04 25 23 24.70 -44 13.6 2.036 1.905 68.1 29.3 15.3 2027 05 05 23 43.32 -49 02.4 1.776 1.827 76.6 32.5 14.8 2027 05 15 00 10.59 -55 47.4 1.526 1.755 85.0 35.0 14.4 2027 05 25 01 01.26 -64 54.3 1.307 1.689 92.6 36.8 13.9 2027 06 04 03 18.67 -74 29.5 1.147 1.632 97.8 38.0 13.5 2027 06 14 07 43.20 -72 01.1 1.081 1.584 98.0 39.4 13.3 2027 06 24 09 39.29 -57 45.9 1.125 1.546 92.3 41.1 13.3 2027 07 04 10 24.13 -43 54.8 1.263 1.520 82.9 41.6 13.5 2027 07 14 10 48.91 -33 17.1 1.459 1.507 72.5 40.0 13.7 2027 07 24 11 05.88 -25 34.7 1.681 1.507 62.3 36.7 14.1 2027 08 03 11 19.06 -19 58.0 1.907 1.520 52.5 32.0 14.4 2027 08 13 11 30.16 -15 46.9 2.123 1.545 43.0 26.6 14.6 2027 08 23 11 39.95 -12 33.3 2.320 1.582 33.7 20.8 14.9 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 August 7 (CBET 5721) Daniel W. E. Green