Electronic Telegram No. 5421 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 N4 (SARNECZKY) Krisztian Sarneczky, Konkoly Observatory, reports the discovery of a slow-moving, small-elongation object in w-band CCD-images obtained on July 14.97 UT with the 0.60-m Schmidt telescope at Piszkesteto Observatory in Hungary. The object was apparently asteroidal on twelve 40-s discovery images and on twenty-four 60-s follow-up images. During follow-up observations on the next night (July 15.96) with the same telescope, thanks to the better seeing, the object immediately and clearly showed a comet-like appearance on three 60-s blinked images. The comet had a condensed, circular coma with diffuse edges, 8" in diameter, with no tail. The relevant astrometry is tabulated below. 2024 UT R.A. (2000) Decl. Mag. Observer July 14.96106 5 41 35.77 +66 21 09.9 19.0 Sarneczky 14.97026 5 41 37.24 +66 21 11.1 19.2 " 14.97945 5 41 38.56 +66 21 12.2 18.9 " 14.99494 5 41 40.67 +66 21 14.3 19.2 " 15.00026 5 41 41.43 +66 21 14.2 19.1 " 15.00557 5 41 42.07 +66 21 15.5 18.9 " 15.01148 5 41 43.00 +66 21 15.9 18.9 " 15.01680 5 41 43.74 +66 21 17.1 19.3 " 15.02806 5 41 45.33 +66 21 18.3 18.9 " 15.03382 5 41 46.12 +66 21 18.9 19.1 " The available astrometry appears on MPEC 2024-O41. The following preliminary parabolic orbital elements by S. Nakano (Central Bureau) are from 72 observations spanning 2024 July 14-22 (mean residual 0".4). There are no close approaches to any major planets. T = 2025 Jan. 6.24387 TT Peri. = 116.25805 Node = 339.62789 2000.0 q = 5.4029600 AU Incl. = 49.77606 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 8.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 06 19 04 41.34 +65 18.9 6.298 5.603 43.4 7.2 18.5 2024 06 29 05 04.42 +65 45.5 6.259 5.584 44.8 7.4 18.5 2024 07 09 05 27.71 +66 08.8 6.211 5.566 46.9 7.7 18.4 2024 07 19 05 50.98 +66 28.9 6.152 5.549 49.7 8.0 18.4 2024 07 29 06 14.04 +66 45.9 6.084 5.533 53.0 8.4 18.4 2024 08 08 06 36.65 +67 00.4 6.007 5.517 56.8 8.8 18.3 2024 08 18 06 58.59 +67 13.1 5.923 5.503 60.9 9.3 18.3 2024 08 28 07 19.62 +67 24.7 5.831 5.489 65.5 9.6 18.2 2024 09 07 07 39.54 +67 36.5 5.734 5.477 70.3 10.0 18.2 2024 09 17 07 58.12 +67 49.5 5.631 5.465 75.4 10.3 18.2 2024 09 27 08 15.14 +68 04.8 5.526 5.455 80.7 10.4 18.1 2024 10 07 08 30.37 +68 23.5 5.418 5.445 86.3 10.6 18.1 2024 10 17 08 43.52 +68 46.4 5.311 5.436 91.9 10.6 18.0 2024 10 27 08 54.33 +69 13.8 5.205 5.429 97.7 10.5 18.0 2024 11 06 09 02.41 +69 45.8 5.105 5.422 103.5 10.2 17.9 2024 11 16 09 07.37 +70 21.3 5.011 5.416 109.1 9.9 17.9 2024 11 26 09 08.79 +70 58.5 4.927 5.412 114.5 9.6 17.8 2024 12 06 09 06.27 +71 34.6 4.855 5.408 119.4 9.1 17.8 2024 12 16 08 59.64 +72 05.4 4.798 5.405 123.6 8.7 17.8 2024 12 26 08 49.09 +72 26.1 4.758 5.404 126.7 8.4 17.7 2025 01 05 08 35.40 +72 31.6 4.736 5.403 128.5 8.2 17.7 2025 01 15 08 20.01 +72 17.7 4.734 5.403 128.7 8.2 17.7 2025 01 25 08 04.70 +71 42.6 4.752 5.405 127.2 8.3 17.7 2025 02 04 07 51.15 +70 46.6 4.791 5.407 124.2 8.7 17.8 2025 02 14 07 40.58 +69 32.5 4.848 5.411 120.0 9.1 17.8 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 July 24 (CBET 5421) Daniel W. E. Green