Electronic Telegram No. 5474 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/2024 V1 (BORISOV) Gennadii Vladimirovich Borisov, Nauchnij, Crimea, reports his discovery of another comet on images obtained on Nov. 8 UT with a 0.50-m f/1.9 astrograph at the MARGO observatory near Nauchnij (discovery observations tabulated below). The object then showed a diffuse coma of diameter about 4" and a broad tail 4"-8" long spanning p.a. 290-310 degrees; the total green magnitude of the comet was 19.8 as measured in a circular aperture of size 0'.25. 2024 UT R.A. (2000) Decl. Mag. Observer Nov. 8.04936 10 54 44.76 +64 41 21.1 19.3 Borisov 8.05997 10 54 45.66 +64 41 18.9 19.8 " 8.07064 10 54 46.68 +64 41 16.9 19.8 " 8.12198 10 54 51.30 +64 41 08.4 19.0 " 8.12861 10 54 51.91 +64 41 07.3 19.5 " 8.13527 10 54 52.47 +64 41 06.3 19.7 " After the comet was posted on the Minor Planet Center's PCCP webpage, L. Buzzi (Varese, Italy) reported that forty-five stacked 60-s CMO-camera images obtained on Nov. 11.14-11.16 UT with a 0.84-m f/3.5 reflector (measured by A. Aletti and Buzzi) show a condensed 6" coma that is elongated toward p.a. about 330 degrees. The available astrometry appears on MPEC 2024-V184 and includes pre- discovery astrometry taken by K. Sarneczky with the Piszkesteto 0.60-m Schmidt telescope on Oct. 28.1 UT (when the comet was apparently asteroidal in appearance and of mag 20.1-20.5), which was sent to the MPC after the comet was posted to the PCCP. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 45 observations spanning Oct. 28-Nov. 11 (mean residual 0".4). There are no close approaches to any major planets. T = 2025 Apr. 2.91149 TT Peri. = 167.37497 Node = 328.72632 2000.0 q = 2.3506947 AU Incl. = 54.52498 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 10 17 10 12.19 +66 12.1 2.932 2.986 83.4 19.4 19.6 2024 10 27 10 33.62 +65 25.8 2.791 2.922 87.5 19.9 19.5 2024 11 06 10 51.52 +64 47.8 2.649 2.860 92.0 20.3 19.3 2024 11 16 11 05.66 +64 21.2 2.508 2.801 96.7 20.5 19.1 2024 11 26 11 15.62 +64 08.1 2.369 2.744 101.7 20.6 18.9 2024 12 06 11 20.65 +64 09.7 2.232 2.690 106.9 20.5 18.7 2024 12 16 11 19.67 +64 24.0 2.100 2.639 112.5 20.2 18.5 2024 12 26 11 11.37 +64 45.2 1.977 2.591 118.2 19.5 18.3 2025 01 05 10 54.41 +65 00.8 1.865 2.547 123.8 18.7 18.1 2025 01 15 10 28.51 +64 49.7 1.768 2.506 129.0 17.8 17.9 2025 01 25 09 55.90 +63 46.0 1.692 2.470 132.9 17.0 17.8 2025 02 04 09 21.64 +61 28.2 1.641 2.438 134.8 16.7 17.7 2025 02 14 08 51.56 +57 51.9 1.619 2.411 133.9 17.2 17.6 2025 02 24 08 29.01 +53 13.0 1.627 2.389 130.2 18.4 17.6 2025 03 06 08 14.44 +47 57.4 1.667 2.371 124.3 20.2 17.6 2025 03 16 08 06.73 +42 31.1 1.734 2.359 117.1 22.1 17.7 2025 03 26 08 04.31 +37 13.1 1.826 2.352 109.3 23.6 17.8 2025 04 05 08 05.86 +32 14.0 1.938 2.351 101.4 24.6 17.9 2025 04 15 08 10.34 +27 37.9 2.065 2.355 93.8 25.2 18.0 2025 04 25 08 16.94 +23 24.7 2.202 2.364 86.5 25.1 18.2 2025 05 05 08 25.13 +19 31.9 2.345 2.378 79.5 24.6 18.4 2025 05 15 08 34.49 +15 56.0 2.492 2.397 72.9 23.8 18.5 2025 05 25 08 44.72 +12 33.9 2.639 2.422 66.6 22.6 18.7 2025 06 04 08 55.60 +09 22.4 2.783 2.451 60.6 21.1 18.8 2025 06 14 09 06.95 +06 18.7 2.924 2.485 55.0 19.6 19.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 November 13 (CBET 5474) Daniel W. E. Green