Electronic Telegram No. 5293 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 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-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala on Sept. 7 (discovery observations tabulated below). Four 45-s w-band survey images taken in 1" seeing how a condensed head of size 1".5 (full-width-at-half- maximum) with no tail. 2023 UT R.A. (2000) Decl. Mag. Sept. 7.57001 0 59 56.43 +31 45 19.4 20.1 7.58095 0 59 56.01 +31 45 19.2 20.3 7.59183 0 59 55.58 +31 45 18.8 20.5 7.60272 0 59 55.15 +31 45 18.7 19.7 Weryk identified the comet in numerous pre-discovery Pan-STARRS images on nine nights dating back to July 29.6 UT (when mag 21.6 was measured). Four 45-s w-band survey images taken on July 30.6 in 1".3 seeing show a condensed head of size 1".6 (FWHM) and magnitude 20.9-21.0 and no tail. Sixteen stacked 60-s CCD exposures taken remotely on Sept. 8.3 by H. Sato (Bunkyo-ku, Tokyo, Japan) using 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 19.4 as measured within a circular aperture of radius 4".9. The available astrometry appears on MPEC 2023-R197. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 89 observations spanning 2023 July 29-Sept. 14 (mean residual 0".4). T = 2026 Apr. 14.41232 TT Peri. = 144.33367 Node = 62.54725 2000.0 q = 3.5691365 AU Incl. = 149.31413 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 7.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 08 04 01 16.83 +31 15.5 8.468 8.708 100.4 6.6 19.7 2023 08 14 01 13.12 +31 32.0 8.249 8.645 109.8 6.3 19.6 2023 08 24 01 08.42 +31 42.6 8.042 8.582 119.3 5.9 19.5 2023 09 03 01 02.80 +31 46.3 7.851 8.518 128.6 5.3 19.4 2023 09 13 00 56.34 +31 41.9 7.683 8.454 137.7 4.6 19.3 2023 09 23 00 49.23 +31 28.8 7.540 8.391 146.0 3.8 19.3 2023 10 03 00 41.68 +31 06.7 7.427 8.327 152.5 3.2 19.2 2023 10 13 00 33.96 +30 36.0 7.346 8.263 155.3 2.9 19.2 2023 10 23 00 26.38 +29 57.6 7.298 8.200 153.3 3.1 19.1 2023 11 02 00 19.20 +29 13.3 7.284 8.136 147.2 3.8 19.1 2023 11 12 00 12.67 +28 25.1 7.300 8.072 138.8 4.6 19.1 2023 11 22 00 06.99 +27 35.3 7.345 8.008 129.4 5.5 19.1 2023 12 02 00 02.29 +26 46.3 7.412 7.944 119.5 6.2 19.0 2023 12 12 23 58.62 +26 00.2 7.497 7.880 109.4 6.8 19.0 2023 12 22 23 56.01 +25 18.7 7.595 7.816 99.4 7.1 19.0 2024 01 01 23 54.40 +24 43.1 7.698 7.751 89.5 7.3 19.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 September 15 (CBET 5293) Daniel W. E. Green