Electronic Telegram No. 5308 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 U1 (FULS) David Carson Fuls, Lunar and Planetary Laboratory, University of Arizona, reports his discovery of a new comet on CCD images obtained on Oct. 16 with the Mt. Lemmon Survey 1.5-m reflector (discovery observations tabulated below), the comet noted as having a condensed coma of size 8".8 with a possible broad tail 6".4 long toward p.a. 345 degrees. 2023 UT R.A. (2000) Decl. Mag. Observer Oct. 16.47712 8 01 38.66 -11 46 03.1 19.3 Fuls 16.48186 8 01 38.62 -11 46 06.3 19.1 " 16.48662 8 01 38.59 -11 46 09.1 19.4 " 16.49137 8 01 38.56 -11 46 12.4 19.3 " 16.51422 8 01 38.41 -11 46 26.9 19.6 " 16.51498 8 01 38.40 -11 46 27.3 19.5 " 16.51575 8 01 38.39 -11 46 27.8 19.7 " 16.51651 8 01 38.39 -11 46 28.5 19.5 " After the object was posted on the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) found a strongly condensed coma 10" in diameter with no tail on twelve stacked 60-s CCD exposures taken remotely with a 0.51-m f/6.8 astrograph at Siding Spring, NSW, Australia; the magnitude was 19.5 as measured within a circular aperture of radius 6".6. The available astrometry appears on MPEC 2023-U288. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 25 observations spanning 2023 Oct. 16-29 (mean residual 0".3). T = 2024 Oct. 13.30685 TT Peri. = 255.75742 Node = 305.82429 2000.0 q = 4.9669732 AU Incl. = 108.16686 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 9.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 10 23 08 00.70 -12 56.0 5.671 5.662 84.4 10.1 18.8 2023 11 02 07 58.12 -14 46.4 5.488 5.627 92.9 10.1 18.7 2023 11 12 07 54.03 -16 38.8 5.312 5.592 101.4 10.0 18.6 2023 11 22 07 48.30 -18 30.7 5.149 5.558 109.5 9.6 18.5 2023 12 02 07 40.90 -20 18.8 5.004 5.525 117.2 9.1 18.4 2023 12 12 07 31.86 -21 59.4 4.883 5.492 123.8 8.6 18.4 2023 12 22 07 21.38 -23 28.1 4.789 5.460 128.9 8.1 18.3 2024 01 01 07 09.80 -24 41.3 4.725 5.430 131.8 7.8 18.2 2024 01 11 06 57.60 -25 36.1 4.692 5.399 131.9 7.8 18.2 2024 01 21 06 45.34 -26 11.1 4.691 5.370 129.4 8.1 18.2 2024 01 31 06 33.63 -26 26.8 4.719 5.342 124.7 8.7 18.2 2024 02 10 06 22.95 -26 25.5 4.772 5.314 118.5 9.4 18.2 2024 02 20 06 13.71 -26 10.4 4.846 5.288 111.4 10.0 18.2 2024 03 01 06 06.12 -25 45.8 4.936 5.262 103.9 10.5 18.2 2024 03 11 06 00.28 -25 15.6 5.035 5.238 96.3 10.9 18.3 2024 03 21 05 56.16 -24 43.5 5.139 5.214 88.8 11.0 18.3 2024 03 31 05 53.65 -24 12.7 5.243 5.191 81.6 11.0 18.3 2024 04 10 05 52.60 -23 45.6 5.342 5.170 74.7 10.8 18.3 2024 04 20 05 52.84 -23 24.4 5.433 5.149 68.4 10.5 18.4 2024 04 30 05 54.19 -23 10.7 5.511 5.129 62.8 10.1 18.4 2024 05 10 05 56.47 -23 05.6 5.576 5.111 57.8 9.6 18.4 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 5308) Daniel W. E. Green