Electronic Telegram No. 5204 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/2022 W3 (LEONARD) Gregory J. Leonard, Lunar and Planetary Laboratory, University of Arizona, reports the discovery of a comet on CCD images taken on 2022 Nov. 26.5 UT with the Mount Lemmon Survey's 1.5-m reflector (discovery observations tabulated below). Four 30-s co-added images show that the comet then showed a moderately condensed coma 6" across with a broad tail 10" long in p.a. 240-260 degrees. 2022 UT R.A. (2000) Decl. Mag. Observer Nov. 26.47759 10 33 26.67 +33 40 13.3 19.7 Leonard 26.48682 10 33 27.01 +33 40 23.4 " 26.49596 10 33 27.35 +33 40 33.5 19.5 " 26.50115 10 33 27.52 +33 40 39.4 19.3 " Four 30-s exposures obtained on Dec. 20.4 UT by K. Wierzchos with the Catalina Sky Survey's 0.68-m Schmidt reflector showed the comet again (unintentionally) in sky that had slight haze; the comet appeared as a very condensed coma of diameter 6" with a broad 12" tail in p.a. 250 degrees. After the comet was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists also commented on the appearance. Five 90-s unfiltered exposures taken on Dec. 23.14-23.15 by F. Kugel with a 0.4-m f/2.8 reflector at Dauban, France, show a 12" tail in p.a. 240 degrees; the magnitude was 18.5-18.6 in an aperture of radius 5".8 (specified as the brightness of the inner coma). Twelve stacked 60-s exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) on Dec. 24.5 with a 0.61-m f/6.5 astrograph located at the Sierra Remote Observatory near Auberry, CA, USA, show a strongly condensed coma 12" in diameter with no tail and with magnitude 18.2; Sato added that the comet had brightened rapidly within a month. Forty stacked 60-s exposures taken by E. Bryssinck (Kruibeke, Belgium) with a 0.4-m f/3.8 reflector on Dec. 26.96 show a central condensation with a diffuse coma 12" in diameter and a tail 18" long toward p.a. 250 degrees; the magnitude was 18.8-19.0 as measured within a circular aperture of radius 5".5. L. Buzzi, Varese, Italy, writes that fifty stacked 15-s exposures taken by himself (and measured by A. Aletti and himself) on 2023 Jan. 6.14-6.16 with a 0.84-m f/3.5 reflector in good conditions but strong moonlight show a condensed coma 6" wide that is elongated for 9" in p.a. about 230 degrees; the magnitude was given as 18.7. The available astrometry (including pre-discovery Pan-STARRS2 observations found subsequent to discovery at mag 21.2-21.7 on 2022 Nov. 13) appears on MPEC 2022-A29. The following nearly parabolic orbital elements by S. Nakano (Central Bureau) are from 168 observations spanning 2022 Nov. 13- 2023 Jan. 10 (mean residual 0".5) and indicate that the comet will pass 0.76 AU from the earth on 2023 Aug. 15 UT. T = 2023 June 22.74531 TT Peri. = 116.50434 e = 0.9954175 Node = 132.27318 2000.0 q = 1.3979311 AU Incl. = 103.56425 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. 2022 12 07 10 39.33 +37 18.7 2.533 2.961 106.0 18.7 18.8 2022 12 17 10 43.24 +41 42.8 2.300 2.858 115.0 18.2 18.5 2022 12 27 10 44.57 +47 09.9 2.092 2.756 123.1 17.4 18.1 2023 01 06 10 41.65 +53 41.2 1.921 2.653 129.1 16.7 17.8 2023 01 16 10 31.16 +61 04.5 1.794 2.551 131.1 16.9 17.5 2023 01 21 10 21.00 +64 56.3 1.749 2.500 130.2 17.5 17.4 2023 01 26 10 05.46 +68 46.2 1.717 2.449 128.0 18.5 17.3 2023 01 31 09 41.77 +72 24.7 1.697 2.398 124.7 19.7 17.2 2023 02 05 09 05.72 +75 38.9 1.689 2.348 120.5 21.2 17.1 2023 02 10 08 12.28 +78 10.4 1.691 2.298 115.7 22.8 17.0 2023 02 15 07 00.64 +79 36.9 1.704 2.248 110.4 24.3 17.0 2023 02 20 05 42.88 +79 45.3 1.724 2.198 105.0 25.7 16.9 2023 02 25 04 37.29 +78 48.4 1.751 2.149 99.5 27.0 16.9 2023 03 02 03 50.50 +77 14.2 1.782 2.101 94.1 28.1 16.8 2023 03 07 03 19.07 +75 26.1 1.817 2.052 88.8 28.9 16.8 2023 03 12 02 58.00 +73 37.3 1.853 2.005 83.8 29.5 16.8 2023 03 17 02 43.66 +71 54.3 1.889 1.958 78.9 29.9 16.7 2023 03 22 02 33.73 +70 20.3 1.925 1.912 74.3 30.1 16.7 2023 03 27 02 26.72 +68 56.5 1.958 1.867 69.9 30.1 16.6 2023 04 01 02 21.70 +67 43.2 1.988 1.823 65.8 30.0 16.6 2023 04 06 02 18.02 +66 40.0 2.014 1.781 62.1 29.8 16.5 2023 04 11 02 15.27 +65 46.2 2.035 1.739 58.7 29.5 16.5 2023 04 16 02 13.15 +65 01.5 2.050 1.699 55.6 29.2 16.4 2023 04 21 02 11.41 +64 25.0 2.060 1.661 52.9 28.9 16.3 2023 04 26 02 09.86 +63 56.4 2.063 1.624 50.7 28.6 16.3 2023 05 01 02 08.34 +63 34.8 2.059 1.590 48.9 28.5 16.2 2023 05 06 02 06.71 +63 19.8 2.048 1.557 47.6 28.6 16.1 2023 05 11 02 04.84 +63 10.9 2.029 1.528 46.8 28.8 16.0 2023 05 16 02 02.61 +63 07.7 2.002 1.500 46.6 29.3 15.9 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 January 10 (CBET 5204) Daniel W. E. Green