Electronic Telegram No. 5309 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 T3 (FULS) David Carson Fuls, Lunar and Planetary Laboratory, University of Arizona, reports his discovery of a new comet on CCD images obtained on Oct. 15 with the Mt. Lemmon Survey 1.5-m reflector (discovery observations tabulated below), the comet noted as having a very compact coma of size 6".2 with a possible tail in p.a. 255 degrees. 2023 UT R.A. (2000) Decl. Mag. Observer Oct. 15.47208 8 09 17.09 - 0 42 19.0 18.5 Fuls 15.47675 8 09 17.25 - 0 42 20.2 18.9 " 15.48141 8 09 17.35 - 0 42 21.4 18.8 " 15.48609 8 09 17.52 - 0 42 23.8 19.3 " After the comet was posted at the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) noted that eight stacked 120-s CCD exposures taken on Oct. 16.51 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 19.3 as measured within a circular aperture of radius 4".9. The astrometry appears on MPEC 2023-U290. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 39 observations spanning 2023 Oct. 15-25 (mean residual 0".5). T = 2025 Jan. 26.68295 TT Peri. = 306.22099 Node = 245.82531 2000.0 q = 3.3746190 AU Incl. = 27.18353 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 9.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 10 23 08 12.39 -01 32.2 5.339 5.323 83.7 10.7 18.9 2023 11 02 08 15.67 -02 39.7 5.131 5.259 91.9 10.9 18.8 2023 11 12 08 17.90 -03 47.7 4.926 5.196 100.3 10.8 18.7 2023 11 22 08 18.96 -04 54.7 4.727 5.133 108.9 10.5 18.6 2023 12 02 08 18.79 -05 58.9 4.539 5.070 117.5 9.9 18.4 2023 12 12 08 17.36 -06 58.5 4.365 5.008 126.0 9.2 18.3 2023 12 22 08 14.72 -07 51.1 4.209 4.946 134.2 8.2 18.2 2024 01 01 08 10.99 -08 34.8 4.075 4.884 141.6 7.2 18.1 2024 01 11 08 06.40 -09 07.4 3.966 4.823 147.4 6.3 18.0 2024 01 21 08 01.28 -09 27.6 3.883 4.763 150.3 5.9 17.9 2024 01 31 07 56.03 -09 34.9 3.827 4.703 149.6 6.1 17.8 2024 02 10 07 51.08 -09 29.7 3.798 4.644 145.4 6.9 17.7 2024 02 20 07 46.83 -09 13.5 3.794 4.585 138.9 8.2 17.7 2024 03 01 07 43.66 -08 48.5 3.813 4.527 131.2 9.5 17.7 2024 03 11 07 41.82 -08 17.6 3.850 4.470 123.0 10.7 17.6 2024 03 21 07 41.48 -07 43.6 3.903 4.413 114.7 11.8 17.6 2024 03 31 07 42.70 -07 09.2 3.968 4.357 106.4 12.7 17.6 2024 04 10 07 45.47 -06 36.9 4.040 4.302 98.4 13.3 17.6 2024 04 20 07 49.74 -06 08.6 4.116 4.248 90.7 13.7 17.6 2024 04 30 07 55.39 -05 45.9 4.193 4.195 83.2 13.8 17.6 2024 05 10 08 02.32 -05 29.9 4.268 4.143 76.1 13.7 17.6 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 5309) Daniel W. E. Green