Electronic Telegram No. 5311 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 V1 (LEMMON) A comet has been discovered at Mt. Lemmon using the 1.5-m reflector (observer J. B. Fazekas) and the 1.0-m Steward Observatory reflector (observer R. A. Kowalski, with Kowalski's observations reported first to the Minor Planet Center); the discovery observations are tabulated below. Fazekas reported that four 30-s exposures show an obvious comet with an 8" coma and no obvious tail; Kowalski reported a diffuse 20" coma with no tail. 2023 UT R.A. (2000) Decl. Mag. Observer Nov. 2.16917 22 20 27.15 +40 06 58.0 20.5 Fazekas 2.17433 22 20 26.99 +40 06 56.2 21.0 " 2.17950 22 20 26.85 +40 06 54.7 20.9 " 2.18466 22 20 26.65 +40 06 53.6 20.9 " 2.23372 22 20 24.75 +40 06 38.8 20.3 Kowalski 2.24051 22 20 24.46 +40 06 36.3 20.8 " 2.24710 22 20 24.26 +40 06 34.7 21.3 " 2.25357 22 20 23.98 +40 06 33.3 20.3 " P. Veres, MPC, relates that he started with the above observations and searched the MPC's "isolated tracklet file" (ITF) for possible pre-discovery observations, which resulted in his finding Mt. Lemmon Survey images of this comet on separate nights (previously unlinked) from Sept. 9 (mag 21.1-21.5), Sept. 21 (mag 20.9-21.9), Oct. 4 (mag 20.2-21.0), and Oct. 21 (mag 20.7-21.2). Veres also found Oct. 22 images (mag 21.1-21.2) in the ITF that were taken with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala. Veres then noticed a nearly parabolic orbit for these observations and posted it to the MPC's PCCP webpage. After the comet was posted to the PCCP webpage, R. Weryk (Department of Physics and Astronomy, University of Western Ontario) writes that he identified pre-discovery images of this comet in Pan-STARRS1 1.8-m reflector observations from Aug. 2 UT (mag 21.5-22.7), Aug. 23 (mag 21.4-21.8), and Sept. 29 (mag 21.6), as well as on Oct. 27 (Pan-STARRS2 1.8-m reflector; mag 20.4). He adds that four 45-s stacked w-band survey Pan-STARRS1 images taken on Oct. 22.25-22.32 UT (which had been in the ITF) show a diffuse coma of size 1".6 (full-width-at-half-maximum) in 1".4 seeing with no obvious tail. The available astrometry appears on MPEC 2023-V23. The following orbital elements by S. Nakano (Central Bureau) are from 41 observations spanning 2023 Aug. 2-Nov. 2 (mean residual 0".3), with corresponding "original" and "future" values of 1/a being +0.000644 and +0.000768 (+/- 0.000022) AU**-1, respectively. Epoch = 2025 July 24.0 TT T = 2025 July 13.06633 TT Peri. = 103.32185 e = 1.0004488 Node = 15.04281 2000.0 q = 5.0921812 AU Incl. = 102.01295 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 10.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 10 23 22 27.61 +40 54.7 6.252 6.898 127.0 6.6 20.7 2023 11 02 22 20.56 +40 07.8 6.286 6.851 121.0 7.1 20.7 2023 11 12 22 14.96 +39 18.5 6.339 6.804 114.1 7.6 20.7 2023 11 22 22 10.84 +38 30.2 6.407 6.757 106.7 8.0 20.7 2023 12 02 22 08.15 +37 46.0 6.484 6.711 99.1 8.3 20.7 2023 12 12 22 06.81 +37 08.2 6.567 6.665 91.4 8.5 20.7 2023 12 22 22 06.66 +36 38.7 6.651 6.619 83.9 8.5 20.7 2024 01 01 22 07.57 +36 18.8 6.731 6.574 76.6 8.4 20.7 2024 01 11 22 09.35 +36 09.4 6.804 6.529 69.7 8.1 20.7 2024 01 21 22 11.87 +36 11.0 6.866 6.485 63.4 7.8 20.7 2024 01 31 22 14.95 +36 23.7 6.915 6.441 57.6 7.4 20.7 2024 02 10 22 18.44 +36 47.4 6.947 6.397 52.7 7.0 20.7 2024 02 20 22 22.21 +37 22.1 6.962 6.354 48.7 6.7 20.6 2024 03 01 22 26.09 +38 07.4 6.959 6.311 46.0 6.5 20.6 2024 03 11 22 29.97 +39 03.0 6.937 6.269 44.7 6.4 20.6 2024 03 21 22 33.68 +40 08.5 6.896 6.227 44.7 6.5 20.5 2024 03 31 22 37.08 +41 23.4 6.837 6.186 46.1 6.7 20.5 2024 04 10 22 40.01 +42 47.1 6.761 6.145 48.6 7.0 20.5 2024 04 20 22 42.29 +44 19.1 6.669 6.104 52.1 7.5 20.4 2024 04 30 22 43.71 +45 58.7 6.565 6.065 56.3 7.9 20.3 2024 05 10 22 44.05 +47 44.8 6.449 6.025 61.0 8.4 20.3 2024 05 20 22 43.01 +49 36.2 6.325 5.987 66.1 8.9 20.2 2024 05 30 22 40.29 +51 31.2 6.196 5.949 71.3 9.3 20.2 2024 06 09 22 35.52 +53 27.6 6.064 5.911 76.6 9.6 20.1 2024 06 19 22 28.30 +55 22.4 5.933 5.874 81.8 9.9 20.0 2024 06 29 22 18.23 +57 11.6 5.806 5.838 86.8 10.0 19.9 2024 07 09 22 04.99 +58 50.4 5.687 5.802 91.4 10.1 19.9 2024 07 19 21 48.47 +60 13.1 5.578 5.767 95.7 10.1 19.8 2024 07 29 21 28.94 +61 13.6 5.481 5.733 99.2 10.1 19.8 2024 08 08 21 07.16 +61 46.7 5.400 5.699 102.1 10.0 19.7 2024 08 18 20 44.42 +61 48.9 5.336 5.666 104.0 10.0 19.7 2024 08 28 20 22.25 +61 19.9 5.290 5.634 104.9 10.0 19.6 2024 09 07 20 02.06 +60 22.4 5.261 5.603 104.7 10.0 19.6 2024 09 17 19 44.84 +59 02.0 5.250 5.572 103.6 10.1 19.6 2024 09 27 19 31.02 +57 25.7 5.255 5.542 101.5 10.2 19.6 2024 10 07 19 20.59 +55 40.4 5.273 5.513 98.7 10.3 19.5 2024 10 17 19 13.29 +53 52.7 5.303 5.485 95.3 10.4 19.5 2024 10 27 19 08.69 +52 08.0 5.340 5.458 91.5 10.5 19.5 2024 11 06 19 06.37 +50 30.6 5.383 5.431 87.5 10.5 19.5 2024 11 16 19 05.92 +49 03.9 5.427 5.405 83.5 10.5 19.5 2024 11 26 19 06.95 +47 50.2 5.470 5.381 79.6 10.4 19.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 November 4 (CBET 5311) Daniel W. E. Green