Electronic Telegram No. 5291 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/2023 P1 (NISHIMURA) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports his identification of pre-discovery stellar images of this comet (cf. CBETs 5285, 5290) in images obtained with the Pan-STARRS1 (Jan. 25) and Pan-STARRS2 (Jan. 19 and 24) 1.8-m Ritchey-Chretien reflectors at Haleakala, with his astrometry tabulated below. 2023 UT R.A. (2000) Decl. Mag. Jan. 19.32603 5 42 40.33 - 9 31 06.1 21.6 19.33829 5 42 39.40 - 9 31 02.1 21.2 19.35041 5 42 38.42 - 9 30 57.8 21.4 19.36261 5 42 37.45 - 9 30 53.9 21.4 24.27852 5 36 20.38 - 9 01 06.3 22.2 24.28988 5 36 19.52 - 9 01 02.0 22.2 24.30127 5 36 18.65 - 9 00 57.4 22.1 24.31266 5 36 17.78 - 9 00 53.2 22.2 25.26478 5 35 06.87 - 8 54 38.8 25.27888 5 35 05.80 - 8 54 32.8 22.7 25.29296 5 35 04.75 - 8 54 27.7 23.2 Also, Hirohisa Sato has reported the following new astrometry from CCD images taken using a 0.25-m f/4 reflector at Sukagawa, Japan. Thirteen stacked 45-s exposures show a strongly condensed a coma about 5'.2 in diameter and a tail more than 17' long (extending beyond the field-of-view) toward p.a. about 287 degrees. 2023 UT R.A. (2000) Decl. Mag. Observer Aug. 28.77819 8 16 28.54 +23 07 04.2 7.5 Sato 28.78133 8 16 29.81 +23 07 07.3 " 28.78512 8 16 31.35 +23 07 10.8 " The January observations above show residuals of +15" in R.A. and -26" in Decl. with respect to the orbit on CBET 5290. The following updated orbital elements by S. Nakano (Central Bureau) are from 402 observations spanning 2023 Jan. 19-Aug. 28 (mean residual 0".6), with indicated orbital period 437 years and corresponding original and future values of 1/a being +0.017407 and +0.018131 (+/- 0.000031) AU**-1, respectively. The comet passed 4.16 AU from Jupiter on 2023 July 19 UT. These elements suggest that this comet passed perihelion previously around the years 302, 723, 1169 (April), and 1588 (July); Nakano noticed some similarity in the elements of comet C/1558 P1, but the node is very different. Epoch = 2023 Sept. 13.0 TT T = 2023 Sept. 17.64148 TT Peri. = 116.29686 e = 0.9960880 Node = 66.83421 2000.0 q = 0.2251598 AU Incl. = 132.47647 The following ephemeris by the undersigned from the above orbital elements uses the same photometric power-law parameters as on CBET 5290 and is little changed from that ephemeris: Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 08 04 06 45.59 +17 23.1 1.952 1.196 30.6 25.6 10.1 2023 08 14 07 10.53 +19 21.2 1.649 0.990 34.1 35.1 9.1 2023 08 24 07 48.73 +21 50.0 1.326 0.767 35.2 49.4 7.7 2023 09 03 08 59.96 +24 09.4 1.009 0.524 30.1 75.0 5.8 2023 09 13 11 21.34 +18 02.7 0.839 0.279 13.9 119.6 3.2 2023 09 23 12 51.79 -04 20.2 1.132 0.294 14.2 57.2 4.0 2023 10 03 12 56.84 -16 10.2 1.459 0.542 13.7 26.0 6.7 2023 10 13 12 56.18 -22 50.8 1.696 0.784 15.8 20.2 8.3 2023 10 23 12 55.71 -27 46.2 1.873 1.005 20.7 20.4 9.4 2023 11 02 12 55.21 -31 56.0 2.005 1.210 27.1 22.0 10.2 2023 11 12 12 54.06 -35 44.1 2.102 1.403 34.5 23.5 10.8 2023 11 22 12 51.49 -39 21.8 2.168 1.585 42.3 24.8 11.3 2023 12 02 12 46.67 -42 54.2 2.211 1.758 50.6 25.7 11.7 2023 12 12 12 38.59 -46 22.1 2.234 1.925 59.1 26.1 12.0 2023 12 22 12 25.99 -49 42.2 2.245 2.085 67.9 25.9 12.3 2024 01 01 12 07.52 -52 45.8 2.249 2.240 76.8 25.3 12.6 2024 01 11 11 42.07 -55 18.6 2.254 2.390 85.6 24.2 12.8 2024 01 21 11 09.55 -57 00.6 2.268 2.536 94.1 22.8 13.0 2024 01 31 10 32.12 -57 31.9 2.296 2.678 101.9 21.1 13.2 2024 02 10 09 54.08 -56 42.5 2.345 2.817 108.4 19.4 13.4 2024 02 20 09 20.18 -54 38.3 2.420 2.953 113.2 17.9 13.7 2024 03 01 08 53.25 -51 39.8 2.523 3.086 115.8 16.8 13.9 2024 03 11 08 33.73 -48 11.9 2.654 3.216 116.0 16.1 14.2 2024 03 21 08 20.75 -44 36.3 2.811 3.343 114.1 15.8 14.4 2024 03 31 08 12.98 -41 08.6 2.992 3.469 110.4 15.7 14.7 2024 04 10 08 09.20 -37 57.9 3.191 3.592 105.5 15.6 15.0 2024 04 20 08 08.43 -35 09.3 3.406 3.713 99.9 15.5 15.2 2024 04 30 08 09.89 -32 44.4 3.630 3.832 93.9 15.2 15.5 2024 05 10 08 13.02 -30 43.0 3.860 3.950 87.7 14.8 15.7 2024 05 20 08 17.38 -29 03.9 4.092 4.066 81.4 14.2 15.9 2024 05 30 08 22.64 -27 45.4 4.322 4.180 75.2 13.6 16.1 2024 06 09 08 28.54 -26 45.8 4.547 4.293 69.2 12.8 16.4 2024 06 19 08 34.88 -26 03.4 4.764 4.404 63.4 11.9 16.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 August 29 (CBET 5291) Daniel W. E. Green