Electronic Telegram No. 5348 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 C1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala, Hawaii, on Feb. 9 (discovery observations tabulated below); four 45-s w-band survey images taken in 0".9-1".1 seeing show a very condensed head of size 1".3 (full-width- at-half-maximum) with a clear tail 6" long towards p.a. 285 degrees. 2024 UT R.A. (2000) Decl. Mag. Feb. 9.40398 10 51 12.81 +25 17 43.2 21.2 9.41691 10 51 12.50 +25 17 46.7 21.1 9.42983 10 51 12.20 +25 17 50.2 21.2 9.44280 10 51 11.89 +25 17 53.8 21.2 9.52931 10 51 09.85 +25 18 16.8 21.2 9.53013 10 51 09.81 +25 18 17.0 21.1 Weryk then identified Pan-STARRS2 pre-discovery images of the comet taken on 2023 Dec. 12.6 UT (mag 22.2-22.8), 2024 Jan. 20.5 (mag 21.4-21.6), and Feb. 4.41-4.45 (mag 20.7-21.1), as well as on pre-discovery images taken with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on 2024 Jan. 21.5 (mag 21.1-22.1). Four 45-s w-band survey images taken in 1".1-1".2 seeing on Jan. 20 show a very condensed head of size 1".5 (FWHM) and a 3" tail toward p.a. 280 degrees. Four 45-s w-band survey images taken in 1".8-2".1 seeing on Feb. 4 show a very condensed head of size 2".2 (FWHM) and a 4" tail toward p.a. 280 degrees. Four 45-s Pan-STARRS2 w-band survey images taken in 1".5 seeing on Feb. 10.4 show a very condensed head of size 1".7 (FWHM) with a tail about 5" long toward p.a. 285 deg. After the comet was posted on the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) reported that twelve stacked 120-s CCD exposures taken remotely on Feb. 11.5 UT with a 0.43-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 20.8 as measured within a circular aperture of radius 5".7. The available astrometry appears on MPEC 2024-C177. The following two- body orbital elements by S. Nakano (Central Bureau) are from 30 observations spanning 2023 Dec. 12-2024 Feb. 13 (mean residual 0".2). T = 2024 Aug. 31.32081 TT Peri. = 94.52184 e = 0.5819645 Node = 83.81504 2000.0 q = 4.4122988 AU Incl. = 14.22718 a = 10.5548427 AU n = 0.02874262 P = 34.29 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 01 11 10 57.41 +23 07.2 3.933 4.643 131.5 9.1 21.3 2024 01 21 10 56.54 +23 49.5 3.817 4.625 141.1 7.7 21.2 2024 01 31 10 54.34 +24 34.9 3.724 4.607 150.4 6.1 21.2 2024 02 10 10 50.98 +25 20.4 3.657 4.590 158.5 4.5 21.1 2024 02 20 10 46.79 +26 02.2 3.619 4.573 162.9 3.6 21.1 2024 03 01 10 42.17 +26 36.9 3.609 4.557 160.9 4.1 21.1 2024 03 11 10 37.57 +27 01.9 3.628 4.542 154.1 5.5 21.1 2024 03 21 10 33.45 +27 15.2 3.674 4.528 145.3 7.2 21.1 2024 03 31 10 30.22 +27 16.3 3.743 4.514 135.9 8.9 21.1 2024 04 10 10 28.16 +27 05.2 3.832 4.502 126.6 10.3 21.1 2024 04 20 10 27.47 +26 43.0 3.938 4.490 117.4 11.5 21.2 2024 04 30 10 28.20 +26 10.8 4.056 4.479 108.5 12.3 21.3 2024 05 10 10 30.35 +25 30.1 4.183 4.469 99.9 12.9 21.3 2024 05 20 10 33.85 +24 42.0 4.315 4.459 91.6 13.1 21.4 2024 05 30 10 38.57 +23 47.9 4.447 4.451 83.6 13.1 21.4 2024 06 09 10 44.38 +22 48.6 4.579 4.443 75.9 12.8 21.5 2024 06 19 10 51.15 +21 45.0 4.706 4.436 68.5 12.3 21.5 2024 06 29 10 58.75 +20 37.9 4.828 4.430 61.3 11.6 21.6 2024 07 09 11 07.05 +19 28.0 4.941 4.425 54.3 10.8 21.6 2024 07 19 11 15.94 +18 15.7 5.044 4.421 47.4 9.7 21.7 2024 07 29 11 25.33 +17 01.7 5.136 4.417 40.8 8.6 21.7 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 February 15 (CBET 5348) Daniel W. E. Green