Electronic Telegram No. 5307 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/2023 Q2 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below, the last two having been made with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala. 2023 UT R.A. (2000) Decl. Mag. Aug. 23.25322 18 15 42.95 +51 55 52.0 21.1 23.26593 18 15 42.14 +51 55 37.0 21.1 23.27863 18 15 41.33 +51 55 21.9 21.6 23.29131 18 15 40.49 +51 55 06.7 21.1 23.38223 18 15 34.58 +51 53 18.1 20.8 23.38305 18 15 34.53 +51 53 17.1 21.1 Weryk writes that four 60-s gri-band follow-up images obtained on Sept. 9.24 UT with the 3.6-m Canada-France-Hawaii Telescope (queue observer A. Acohido) shows this to be clearly a comet; in the best image (0".6 seeing), there is a very condensed head of size 0".7 (full-width-at-half-maximum) with a broad tail 3" long spanning p.a. 65-120 degrees. Four additional 60-s CFHT exposures obtained on Oct. 13.2 (queue observer L. Wells; queue coordinator T. Burdullis) in 1".0 seeing show a very condensed head of size 1".1 (FWHM) and a broad tail > 10" long spanning p.a. 30-100 degrees. After the comet was posted on the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) reported that twenty-four stacked 60-s CCD exposures taken on Sept. 6.2 UT with a 0.51-m f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) show only a stellar appearance; the magnitude was 20.2 as measured within a circular aperture of radius 4".9. The astrometry appears on MPEC 2023-U285 and includes pre-discovery Pan-STARRS2 observations from July 6.6 UT (magnitude 21.1-21.2) that were found later. The following orbital elements by S. Nakano (Central Bureau) are from 120 observations spanning 2023 July 6-Oct. 29 (mean residual 0".4), with corresponding original and future values of 1/a being +0.002971 and +0.003341 (+/- 0.000017) AU**-1, respectively. Epoch = 2024 June 19.0 TT T = 2024 June 24.04929 TT Peri. = 171.71693 e = 0.9908317 Node = 92.67885 2000.0 q = 3.2094775 AU Incl. = 104.05866 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. 2023 10 23 18 03.16 +30 08.0 4.105 3.947 73.9 14.0 19.3 2023 10 28 18 05.34 +28 31.4 4.132 3.921 70.9 13.9 19.3 2023 11 02 18 07.81 +26 58.4 4.159 3.895 67.9 13.7 19.3 2023 11 07 18 10.53 +25 29.3 4.186 3.869 64.8 13.4 19.3 2023 11 12 18 13.49 +24 04.3 4.212 3.844 61.7 13.1 19.3 2023 11 17 18 16.66 +22 43.3 4.238 3.819 58.7 12.8 19.3 2023 11 22 18 20.00 +21 26.4 4.262 3.794 55.7 12.4 19.3 2023 11 27 18 23.49 +20 13.6 4.284 3.770 52.8 12.0 19.3 2023 12 02 18 27.12 +19 04.8 4.304 3.746 49.9 11.6 19.3 2023 12 12 18 34.68 +16 59.1 4.335 3.700 44.6 10.8 19.2 2023 12 22 18 42.52 +15 08.5 4.352 3.655 40.1 10.0 19.2 2024 01 01 18 50.49 +13 31.9 4.352 3.611 36.7 9.4 19.2 2024 01 11 18 58.45 +12 08.1 4.333 3.570 34.8 9.0 19.1 2024 01 21 19 06.25 +10 55.7 4.294 3.530 34.7 9.1 19.0 2024 01 31 19 13.76 +09 53.2 4.234 3.492 36.5 9.7 19.0 2024 02 10 19 20.83 +08 59.0 4.153 3.456 40.1 10.6 18.9 2024 02 20 19 27.30 +08 11.4 4.050 3.423 45.0 11.8 18.8 2024 02 25 19 30.26 +07 49.4 3.991 3.407 47.8 12.4 18.8 2024 03 01 19 33.01 +07 28.4 3.927 3.391 50.9 13.1 18.7 2024 03 06 19 35.52 +07 07.9 3.858 3.376 54.3 13.8 18.7 2024 03 11 19 37.77 +06 47.9 3.785 3.362 57.8 14.5 18.6 2024 03 16 19 39.72 +06 27.8 3.708 3.348 61.4 15.1 18.5 2024 03 21 19 41.35 +06 07.5 3.626 3.335 65.3 15.7 18.5 2024 03 26 19 42.63 +05 46.4 3.542 3.322 69.3 16.3 18.4 2024 03 31 19 43.52 +05 24.3 3.454 3.310 73.4 16.8 18.4 2024 04 05 19 43.99 +05 00.6 3.364 3.299 77.7 17.2 18.3 2024 04 10 19 43.99 +04 35.0 3.271 3.288 82.2 17.6 18.2 2024 04 15 19 43.48 +04 06.9 3.177 3.278 86.8 17.8 18.1 2024 04 20 19 42.42 +03 35.8 3.083 3.269 91.6 17.9 18.1 2024 04 25 19 40.75 +03 01.0 2.988 3.260 96.6 17.8 18.0 2024 04 30 19 38.44 +02 22.0 2.894 3.252 101.7 17.7 17.9 2024 05 05 19 35.43 +01 38.1 2.802 3.245 107.1 17.3 17.8 2024 05 10 19 31.68 +00 48.6 2.712 3.238 112.7 16.7 17.7 2024 05 15 19 27.14 -00 07.0 2.626 3.232 118.4 16.0 17.7 2024 05 20 19 21.79 -01 09.4 2.545 3.227 124.4 15.0 17.6 2024 05 25 19 15.60 -02 18.8 2.469 3.222 130.7 13.8 17.5 2024 05 30 19 08.58 -03 35.6 2.401 3.218 137.1 12.4 17.5 2024 06 04 19 00.74 -04 59.7 2.342 3.215 143.6 10.8 17.4 2024 06 09 18 52.13 -06 30.7 2.291 3.213 150.3 9.0 17.4 2024 06 14 18 42.83 -08 07.8 2.252 3.211 156.9 7.1 17.3 2024 06 19 18 32.97 -09 49.9 2.224 3.210 163.1 5.3 17.3 2024 06 24 18 22.69 -11 35.5 2.209 3.209 167.9 3.8 17.3 2024 06 29 18 12.15 -13 22.6 2.206 3.210 169.1 3.4 17.3 2024 07 04 18 01.55 -15 09.7 2.216 3.211 165.6 4.5 17.3 2024 07 09 17 51.08 -16 54.8 2.239 3.213 159.9 6.3 17.3 2024 07 14 17 40.94 -18 36.5 2.274 3.215 153.3 8.2 17.3 2024 07 19 17 31.28 -20 13.7 2.321 3.218 146.6 10.0 17.4 2024 07 24 17 22.25 -21 45.5 2.378 3.222 140.0 11.7 17.4 2024 07 29 17 13.94 -23 11.6 2.444 3.227 133.4 13.2 17.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 October 30 (CBET 5307) Daniel W. E. Green