Electronic Telegram No. 5248 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 F1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on Mar. 27 UT with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). 2023 UT R.A. (2000) Decl. Mag. Mar. 27.59582 15 51 13.42 - 3 29 10.3 20.8 27.60624 15 51 11.28 - 3 29 12.7 21.0 27.61667 15 51 09.15 - 3 29 14.9 21.0 27.62709 15 51 06.99 - 3 29 17.1 20.9 Weryk adds that three 60-s gri-band follow-up images obtained on Mar. 28.5 UT with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea by queue observer L. Wells (coordinator E. Bertin) show a very condensed coma of size 0".9 (full-width-at-half-maximum) of mag 20.8-20.9 in 0".8 seeing (and no tail), with the point-spread function showing a soft appearance. Three additional 60-s CFHT exposures taken on Apr. 15.53 (queue observer H. Januszewski; coordinator T. Burdullis) show a very condensed 1".25 coma (FWHM) in 1".17 seeing with an 8" tail in p.a. 30-60 degrees. Pre-discovery observations from Mar. 18.6 UT were identified on images obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala, with the magnitude given as 21.2-21.7. After the comet was posted to the Minor Planet Center's PCCP webpage, other CCD astrometrists reported on the comet's appearance. Forty stacked 20-s exposures obtained by H. Sato (Bunkyo-ku, Tokyo, Japan) using a 0.51-m f/6.8 astrograph located at Deep Sky Chile, Rio Hurtado, Chile, on Mar. 29.4 UT show only a stellar appearance; the magnitude was 20.8 as measured within a circular aperture of radius 2".2. L. Buzzi, Varese, Italy, writes that two-hundred-seventy-seven stacked 20-s exposures taken on Apr. 16.1 by A. Aletti and F. Bellini with a 0.36-m f/7.5 reflector in good conditions show a slightly condensed coma 10" wide of mag 19.0, elongated in p.a. 85 degrees; the FWHM is larger than that of stars of similar brightness (5".0 vs. 4".0). The available astrometry appears on MPEC 2023-H184. The following elliptical orbital elements by S. Nakano (Central Bureau) are from 166 observations spanning 2023 Mar. 18-Apr. 25 (mean residual 0".4). The comet will pass 2.38 AU from Jupiter on 2024 July 3 UT. T = 2023 June 28.36700 TT Peri. = 216.66270 e = 0.9932349 Node = 25.24776 2000.0 q = 1.7080501 AU Incl. = 131.75034 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 16.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 04 16 14 09.73 -04 56.7 0.959 1.955 169.9 5.1 18.2 2023 04 26 12 53.87 -05 33.3 0.921 1.896 159.3 10.8 18.0 2023 05 06 11 43.19 -05 47.6 1.001 1.844 133.1 23.5 18.1 2023 05 16 10 51.07 -05 52.2 1.166 1.800 111.3 31.6 18.4 2023 05 26 10 16.81 -06 02.2 1.374 1.763 94.0 35.0 18.7 2023 06 05 09 54.97 -06 22.7 1.596 1.735 79.9 35.1 18.9 2023 06 15 09 41.04 -06 53.7 1.815 1.717 68.1 33.3 19.2 2023 06 25 09 32.13 -07 34.5 2.020 1.709 57.7 30.2 19.4 2023 07 05 09 26.42 -08 24.3 2.202 1.710 48.6 26.5 19.6 2023 07 15 09 22.77 -09 22.8 2.359 1.722 40.8 22.7 19.8 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 April 26 (CBET 5248) Daniel W. E. Green