Electronic Telegram No. 5700 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 L1 (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 June 8 (discovery observations tabulated below). Four 45-s stacked w-band survey images taken in 1".5-1".8 seeing show a condensed head of size 2".1 (full-width-at-half- maximum) with a broad tail 4" long spanning p.a. 230-290 degrees. 2026 UT R.A. (2000) Decl. Mag. June 8.54946 20 43 58.62 - 0 32 02.9 20.0 8.55832 20 43 58.51 - 0 32 05.7 19.9 8.56719 20 43 58.42 - 0 32 07.9 20.1 8.57639 20 43 58.30 - 0 32 10.5 20.2 Weryk then found pre-discovery images of this comet on three nights (May 25.6, 29.6, and 30.6 UT), all at mag 19.7-19.9. A 27-s i-band survey image from May 25 taken in 1".0 seeing shows a very condensed head of size 1".5 (FWHM) with a suspected 2" tail to the west. Three 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 June 9.49 UT in 0".8 seeing (queue observer J. Silva; queue coordinator J. Ou) show a condensed head of size 1".5 (FWHM) and a broad tail 10" long spanning p.a. 290-310 degrees. The available astrometry appears on MPEC 2026-L49 (including pre- discovery astrometry from Mt. Lemmon dating back to Apr. 8 at mag 20.9, and Palomar astrometry from June 7 and 8, all of which were reported after Weryk's discovery was posted to the Minor Planet Center's PCCP webpage). The following orbital elements by S. Nakano (Central Bureau) are from 38 observations spanning 2026 Apr. 8-June 9 (mean residual 0".3). There are no close approaches to major planets. T = 2027 Apr. 11.39097 TT Peri. = 200.59363 e = 0.9936820 Node = 130.50415 2000.0 q = 4.8794728 AU Incl. = 67.26248 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 10.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2026 06 09 20 43.89 -00 34.1 4.800 5.419 122.9 9.1 19.3 2026 06 19 20 41.48 -01 25.2 4.645 5.386 132.7 8.0 19.2 2026 06 29 20 37.99 -02 27.9 4.510 5.355 142.7 6.6 19.1 2026 07 09 20 33.59 -03 42.0 4.400 5.324 152.7 5.0 19.0 2026 07 19 20 28.48 -05 06.6 4.319 5.294 161.9 3.4 19.0 2026 07 29 20 22.97 -06 40.0 4.269 5.265 167.6 2.4 18.9 2026 08 08 20 17.39 -08 19.4 4.251 5.237 164.8 2.9 18.9 2026 08 18 20 12.10 -10 01.9 4.267 5.210 156.3 4.5 18.9 2026 08 28 20 07.44 -11 44.3 4.313 5.183 146.2 6.2 18.9 2026 09 07 20 03.72 -13 23.6 4.388 5.158 135.8 7.8 18.9 2026 09 17 20 01.15 -14 57.8 4.486 5.134 125.4 9.2 18.9 2026 09 27 19 59.88 -16 25.0 4.604 5.110 115.1 10.2 19.0 2026 10 07 19 59.99 -17 44.5 4.736 5.088 105.1 10.9 19.0 2026 10 17 20 01.47 -18 55.7 4.876 5.067 95.3 11.3 19.1 2026 10 27 20 04.29 -19 58.8 5.021 5.047 85.8 11.3 19.1 2026 11 06 20 08.35 -20 54.1 5.165 5.028 76.5 11.1 19.2 2026 11 16 20 13.56 -21 42.1 5.304 5.010 67.5 10.5 19.2 2026 11 26 20 19.80 -22 23.3 5.434 4.993 58.7 9.7 19.3 2026 12 06 20 26.94 -22 58.6 5.551 4.977 50.1 8.7 19.3 2026 12 16 20 34.87 -23 28.5 5.654 4.962 41.7 7.6 19.3 2026 12 26 20 43.46 -23 53.9 5.739 4.949 33.5 6.3 19.4 2027 03 16 22 03.52 -26 23.0 5.680 4.884 33.7 6.5 19.3 2027 03 26 22 13.62 -26 50.7 5.584 4.881 41.4 7.8 19.2 2027 04 05 22 23.49 -27 24.5 5.475 4.880 49.2 8.9 19.2 2027 04 15 22 33.03 -28 05.6 5.353 4.880 57.0 9.9 19.1 2027 04 25 22 42.18 -28 55.5 5.221 4.881 64.9 10.8 19.1 2027 05 05 22 50.83 -29 55.2 5.084 4.883 72.9 11.4 19.0 2027 05 15 22 58.89 -31 06.2 4.944 4.886 80.9 11.8 19.0 2027 05 25 23 06.25 -32 29.0 4.804 4.891 88.9 11.9 18.9 2027 06 04 23 12.78 -34 04.3 4.669 4.897 97.0 11.9 18.9 2027 06 14 23 18.34 -35 52.1 4.543 4.904 105.0 11.5 18.8 2027 06 24 23 22.79 -37 51.5 4.429 4.913 112.8 11.0 18.8 2027 07 04 23 25.96 -40 00.8 4.332 4.922 120.2 10.3 18.7 2027 07 14 23 27.70 -42 17.1 4.255 4.933 127.0 9.5 18.7 2027 07 24 23 27.91 -44 36.6 4.200 4.945 132.6 8.7 18.7 2027 08 03 23 26.52 -46 54.6 4.171 4.958 136.7 8.1 18.7 2027 08 13 23 23.56 -49 05.6 4.168 4.973 138.5 7.8 18.7 2027 08 23 23 19.20 -51 04.5 4.191 4.988 137.9 7.8 18.7 2027 09 02 23 13.77 -52 46.8 4.240 5.005 135.0 8.2 18.7 2027 09 12 23 07.75 -54 09.3 4.312 5.022 130.3 8.8 18.8 2027 09 22 23 01.74 -55 10.4 4.405 5.041 124.4 9.5 18.8 2027 10 02 22 56.35 -55 50.3 4.515 5.061 117.9 10.1 18.9 2027 10 12 22 52.12 -56 10.3 4.639 5.082 111.0 10.6 19.0 2027 10 22 22 49.49 -56 12.9 4.772 5.104 103.9 10.9 19.1 2027 11 01 22 48.67 -56 00.9 4.912 5.127 96.9 11.1 19.1 2027 11 11 22 49.78 -55 37.0 5.054 5.151 90.0 11.1 19.2 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 June 9 (CBET 5700) Daniel W. E. Green