Electronic Telegram No. 5450 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 R4 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on Sept. 11 UT with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). Four 45-s w-band survey images taken in 1".2 seeing show a very condensed head of size 1".3 (full-with-at-half-maximum) with no tail. 2024 UT R.A. (2000) Decl. Mag. Sept.11.37094 22 36 03.41 + 8 44 12.8 21.2 11.39265 22 36 02.76 + 8 44 11.7 20.8 11.40594 22 36 02.37 + 8 44 10.9 21.1 11.42163 22 36 01.91 + 8 44 10.1 21.2 11.51632 22 35 59.08 + 8 44 05.1 21.1 11.51698 22 35 59.07 + 8 44 05.1 20.9 Weryk adds that two 60-s w-band follow-up images obtained on Sept. 13.35 UT with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala in 1".0 seeing show a very condensed head of size 1".2 (FWHM) with no tail. Weryk also identified apparently asteroidal pre-discovery Pan-STARRS2 observations from 2024 July 3.54-3.58 (mag 21.8-22.5), July 9.53-5.57 (mag 21.5-23.3), Aug. 6.45-6.48 (maag 21.6-21.7), and Sept. 6.50 (mag 20.7-20.8), as well as Pan-STARRS1 observations on Aug. 13.55-13.57 (mag 21.4-21.8). After the comet was posted on the Minor Planet Center's PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) obtained twenty-eight stacked CCD exposures remotely on Sept. 14.2 UT using a "Deep Sky Chile" 0.51-m f/6.8 astrograph located at Rio Hurtado, Chile, that reveal a strongly condensed coma 4" in diameter with no tail; the magnitude was 20.6 as measured within a circular aperture of radius 2".2. S. Deen (Simi Valley, CA, USA) has identified three stellar images of the comet in archival data obtained with the Cerro Tololo 4-m reflector (+ DECam), on 2024 Aug. 23.24, Aug. 26.15, and Sept. 11.09 UT. The available astrometry appears on MPEC 2024-S12 and includes four apparently asteroidal single-night observations made with the Mt. Lemmon Survey 1.5-m reflector on Sept. 9.24-9.25 UT (magnitude given as 20.6-21.0) and found in the MPC's "isolated tracklet file". The following parabolic orbital elements by S. Nakano (Central Bureau) are from 34 observations spanning 2024 July 3-Sept. 14 (mean residual 0".2). These indicated that the comet passed 2.33 AU from Saturn on 2024 Apr. 8. T = 2027 Oct. 28.23152 TT Peri. = 109.01512 Node = 345.91548 2000.0 q = 4.4128818 AU Incl. = 95.29599 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 8.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 09 07 22 38.21 +08 47.7 8.606 9.578 163.9 1.7 20.5 2024 09 17 22 33.32 +08 38.9 8.568 9.521 160.3 2.0 20.5 2024 09 27 22 28.63 +08 27.6 8.561 9.463 152.7 2.8 20.5 2024 10 07 22 24.31 +08 15.0 8.583 9.405 143.5 3.6 20.5 2024 10 17 22 20.51 +08 02.1 8.631 9.347 133.7 4.4 20.4 2024 10 27 22 17.32 +07 49.9 8.702 9.290 123.7 5.1 20.4 2024 11 06 22 14.84 +07 39.7 8.790 9.232 113.6 5.6 20.4 2024 11 16 22 13.11 +07 32.2 8.891 9.174 103.6 6.0 20.4 2024 11 26 22 12.13 +07 28.2 8.998 9.116 93.7 6.2 20.4 2024 12 06 22 11.90 +07 28.4 9.108 9.058 84.0 6.2 20.5 2024 12 16 22 12.37 +07 33.1 9.214 9.000 74.5 6.0 20.5 2024 12 26 22 13.47 +07 42.5 9.311 8.942 65.1 5.7 20.5 2025 01 05 22 15.14 +07 56.8 9.396 8.884 56.0 5.3 20.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 September 17 (CBET 5450) Daniel W. E. Green