Electronic Telegram No. 5417 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 N3 (SARNECZKY) Krisztian Sarneczky, Konkoly Observatory, reports the discovery of a comet in eleven 60-s stacked w-band images (limiting mag about 20.5) taken on July 8-9 UT at the Piszkesteto Observatory in Hungary with the 0.60-m Schmidt telescope (discovery observations tabulated below). The discovery images show a condensed head slightly more diffuse than nearby stars and 4" in diameter with no tail. Fifteen 60-s stacked follow-up images taken on July 10.0 with the same telescope show a fuzzy coma, slightly elongated in the north-south direction (not in the direction of motion with size about 6" x 8", again with no tail. [Note: the discoverer's name is Kriszti\'an S\'arneczky in TeX form.] 2024 UT R.A. (2000) Decl. Mag. Observer July 8.89672 5 58 15.64 +70 24 52.0 19.6 Sarneczky 8.90593 5 58 16.57 +70 24 55.4 19.6 " 8.96236 5 58 23.46 +70 25 22.1 19.4 " 9.00406 5 58 28.38 +70 25 40.4 19.5 " 9.00938 5 58 29.03 +70 25 42.3 19.4 " 9.01471 5 58 29.60 +70 25 45.5 19.2 " 9.02061 5 58 30.32 +70 25 48.0 19.3 " 9.02594 5 58 31.00 +70 25 50.6 19.5 " 9.03144 5 58 31.67 +70 25 52.7 19.5 " After the comet was placed on the Minor Planet Center's PCCP webpage, other astrometrists sent reports of the comet's appearance to the Central Bureau. L. Buzzi, Varese, Italy, writes that forty-three stacked 60-s CMOS images taken on July 9.95-9.97 UT with a 0.84-m f/3.5 reflector (and measured by Buzzi and A. Aletti) show a somewhat diffuse aspect, with a moderately condensed coma 6" wide and no tail. Twelve stacked 60-s CCD images taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.43-m f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) on July 10.4 show only a stellar apperance; the magnitude was 20.4 as measured within a circular aperture of radius 3".8. P. Veres, Minor Planet Center, found in the MPC's "isolated tracklet file" a possible single night of CCD observations obtained on 2023 Dec. 15.3 UT by M. Holbrook with a 0.36-m f/2.2 reflector showing the apparently stellar object at mag 20.3-20.5. Veres then asked R. Weryk (Department of Physics and Astronomy, University of Western Ontario) to search for possibly confirming pre-discovery images obtained at Haleakala to see if he could find the comet, and Weryk reported apparently asteroidal images from 2023 Oct. 9.6 obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector that confirm the identity with Holbrook's object. The available astrometry appears on MPEC 2024-O11. The following orbital elements by S. Nakano (Central Bureau) are from 99 observations spanning 2023 Oct. 9-2024 July 17 (mean residual 0".4), with corresponding "original" and "future" values of 1/a being +0.000015 and -0.000069 (+/- 0.000012) AU**-1, respectively. There are no close approaches to major planets. Epoch = 2025 Mar. 26.0 TT T = 2025 Apr. 11.42036 TT Peri. = 86.88458 e = 1.0012677 Node = 82.60852 2000.0 q = 5.0144130 AU Incl. = 88.72920 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. 2024 06 19 05 22.56 +68 06.3 6.173 5.500 44.9 7.5 19.4 2024 06 29 05 39.67 +69 13.2 6.117 5.470 46.7 7.8 19.3 2024 07 09 05 58.46 +70 25.7 6.048 5.440 49.3 8.1 19.3 2024 07 19 06 19.21 +71 43.3 5.967 5.411 52.7 8.6 19.2 2024 07 29 06 42.38 +73 05.4 5.876 5.383 56.5 9.1 19.2 2024 08 08 07 08.64 +74 30.9 5.778 5.356 60.8 9.5 19.1 2024 08 18 07 38.93 +75 58.4 5.674 5.330 65.3 9.9 19.1 2024 08 28 08 14.65 +77 25.3 5.568 5.305 69.8 10.3 19.0 2024 09 07 08 57.70 +78 47.9 5.462 5.281 74.4 10.6 19.0 2024 09 17 09 50.22 +80 00.0 5.359 5.257 78.8 10.8 18.9 2024 09 27 10 53.67 +80 53.0 5.261 5.235 83.1 11.0 18.9 2024 10 07 12 06.35 +81 17.1 5.171 5.214 86.9 11.0 18.8 2024 10 17 13 21.59 +81 05.7 5.091 5.193 90.3 11.1 18.8 2024 10 27 14 31.02 +80 19.7 5.024 5.174 93.1 11.1 18.7 2024 11 06 15 29.93 +79 07.5 4.969 5.156 95.3 11.0 18.7 2024 11 16 16 18.16 +77 39.4 4.929 5.139 96.7 11.0 18.7 2024 11 26 16 57.64 +76 04.3 4.903 5.122 97.3 11.0 18.6 2024 12 06 17 30.48 +74 29.2 4.890 5.107 97.2 11.0 18.6 2024 12 16 17 58.30 +72 59.3 4.889 5.093 96.4 11.1 18.6 2024 12 26 18 22.30 +71 38.4 4.899 5.081 95.0 11.1 18.6 2025 01 05 18 43.25 +70 29.3 4.918 5.069 93.2 11.2 18.6 2025 01 15 19 01.65 +69 34.0 4.943 5.058 91.1 11.2 18.6 2025 01 25 19 17.82 +68 53.5 4.971 5.049 88.9 11.2 18.6 2025 02 04 19 31.95 +68 28.4 5.002 5.040 86.6 11.3 18.6 2025 02 14 19 44.05 +68 18.6 5.031 5.033 84.5 11.3 18.6 2025 02 24 19 54.10 +68 23.6 5.058 5.027 82.6 11.3 18.6 2025 03 06 20 01.94 +68 42.6 5.082 5.022 81.0 11.2 18.6 2025 03 16 20 07.32 +69 14.0 5.100 5.019 79.7 11.2 18.6 2025 03 26 20 09.86 +69 56.1 5.112 5.016 78.9 11.3 18.6 2025 04 05 20 09.04 +70 46.4 5.119 5.015 78.4 11.3 18.6 2025 04 15 20 04.20 +71 41.4 5.120 5.014 78.3 11.3 18.6 2025 04 25 19 54.62 +72 36.9 5.116 5.015 78.6 11.3 18.6 2025 05 05 19 39.56 +73 27.1 5.107 5.018 79.2 11.4 18.6 2025 05 15 19 18.75 +74 04.9 5.095 5.021 80.1 11.4 18.6 2025 05 25 18 52.78 +74 22.2 5.082 5.026 81.1 11.5 18.6 2025 06 04 18 23.51 +74 11.5 5.068 5.031 82.2 11.5 18.6 2025 06 14 17 53.97 +73 27.8 5.056 5.038 83.2 11.5 18.6 2025 06 24 17 27.16 +72 10.6 5.048 5.046 84.1 11.6 18.6 2025 07 04 17 05.06 +70 22.7 5.045 5.055 84.8 11.6 18.6 2025 07 14 16 48.33 +68 09.5 5.048 5.066 85.2 11.5 18.7 2025 07 24 16 36.65 +65 37.0 5.059 5.077 85.3 11.5 18.7 2025 08 03 16 29.34 +62 50.8 5.079 5.090 84.9 11.5 18.7 2025 08 13 16 25.59 +59 56.1 5.109 5.103 84.0 11.4 18.7 2025 08 23 16 24.68 +56 57.2 5.148 5.118 82.7 11.3 18.7 2025 09 02 16 26.01 +53 58.1 5.196 5.134 80.9 11.2 18.8 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 July 18 (CBET 5417) Daniel W. E. Green