Electronic Telegram No. 5322 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 X1 (LEONARD) G. J. Leonard, Lunar and Planetary Laboratory, University of Arizona, reports his discovery of a comet on CCD images obtained on Dec. 4 with the Catalina Sky Survey's 0.68-m Schmidt telescope (discovery observations tabulated below). The comet showed a moderately condensed coma about 8" across with no apparent tail in four 30-s co-added images. 2023 UT R.A. (2000) Decl. Mag. Observer Dec. 4.44005 12 39 03.85 +18 23 33.9 17.3 Leonard 4.44205 12 39 04.14 +18 23 43.1 17.6 " 4.44404 12 39 04.31 +18 23 51.0 17.2 " 4.44605 12 39 04.41 +18 23 59.6 17.7 " After the comet was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists also commented on the cometary appearance. A. Hale (Cloudcroft, NM, USA) writes that 180-s exposures taken on Dec. 5.6 UT with a 0.35-m Schmidt-Cassegrain reflector in the Las Cumbres Observatory's Clamshell dome at Haleakala, HI, USA, show a diffuse coma of diameter 1'.2 with no tail; he adds that a small, somewhat bright central condensation was embedded within a larger, diffuse coma. One-hundred-twenty-six stacked 30-s exposures taken on Dec. 6.2 by A. Aletti (and measured with M. Auteri) using a 0.36-m f/7.5 reflector at Varese, Italy, show it to be clearly a comet despite the moon being nearby, with a condensed 25" coma in size (mag 18.3) and no tail. Ten stacked 60-s exposures taken remotely by M. Mattiazzo (Swan Hill, Victoria, Australia) with a 0.43-m f/6.8 reflector (+ luminance filter) located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) on Dec. 6.47 show a diffuse coma 1' with total (UCAC4 V) magnitude 16.8, adding that the moon was situated only 21 degrees from the comet. Twenty- three stacked 60-s exposures taken remotely on Dec. 6.5 by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.25-m f/3.4 astrograph at the Utah Desert Remote Observatory show the comet to be moderately condensed with an outer coma 2'.0 in diameter and no tail; the magnitude was 14.7 as measured within a circular aperture of radius 60".0. The astrometry appears on MPEC 2023-X225. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 123 observations spanning Dec. 4-11 (mean residual 0".5). These elements indicate that the comet passed 1.69 AU from Saturn on 2021 July 15 and 3.48 AU from Jupiter on 2021 Dec. 12 UT. T = 2023 Oct. 18.28550 TT Peri. = 321.83104 Node = 137.09188 2000.0 q = 0.9536441 AU Incl. = 110.62833 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 10 23 11 40.40 -15 37.1 1.656 0.957 31.3 32.7 14.4 2023 10 28 11 45.81 -12 47.7 1.610 0.969 34.4 35.4 14.4 2023 11 02 11 51.49 -09 47.0 1.557 0.988 38.1 38.3 14.4 2023 11 07 11 57.51 -06 32.2 1.497 1.014 42.3 41.1 14.4 2023 11 12 12 03.90 -02 59.9 1.432 1.047 47.0 43.7 14.4 2023 11 17 12 10.74 +00 53.9 1.365 1.085 52.0 45.9 14.5 2023 11 22 12 18.07 +05 13.8 1.297 1.128 57.3 47.5 14.5 2023 11 27 12 25.98 +10 04.6 1.230 1.175 62.9 48.4 14.5 2023 12 02 12 34.57 +15 30.6 1.168 1.225 68.7 48.6 14.5 2023 12 07 12 43.99 +21 35.0 1.114 1.278 74.7 48.1 14.6 2023 12 12 12 54.43 +28 17.7 1.070 1.333 80.8 46.8 14.6 2023 12 17 13 06.19 +35 33.9 1.040 1.390 86.7 45.0 14.7 2023 12 22 13 19.71 +43 12.6 1.026 1.449 92.2 42.7 14.8 2023 12 27 13 35.72 +50 56.8 1.031 1.508 96.9 40.3 15.0 2024 01 01 13 55.43 +58 26.8 1.056 1.569 100.5 38.0 15.2 2024 01 06 14 20.92 +65 23.3 1.099 1.630 102.9 36.0 15.4 2024 01 11 14 56.04 +71 29.5 1.158 1.691 104.0 34.3 15.6 2024 01 16 15 47.84 +76 29.8 1.233 1.753 104.0 33.0 15.9 2024 01 21 17 07.24 +80 04.0 1.320 1.815 103.0 31.9 16.2 2024 01 26 18 56.97 +81 45.9 1.416 1.878 101.4 30.9 16.4 2024 01 31 20 46.53 +81 34.5 1.520 1.940 99.2 30.1 16.7 2024 02 05 22 05.75 +80 17.0 1.630 2.002 96.8 29.3 17.0 2024 02 10 22 57.67 +78 39.5 1.744 2.064 94.1 28.5 17.2 2024 02 15 23 33.15 +77 04.0 1.860 2.126 91.3 27.7 17.5 2024 02 20 23 59.24 +75 38.3 1.979 2.188 88.5 26.8 17.7 2024 02 25 00 19.73 +74 24.5 2.097 2.250 85.6 26.0 17.9 2024 03 01 00 36.73 +73 22.5 2.216 2.311 82.8 25.2 18.1 2024 03 06 00 51.42 +72 31.6 2.334 2.372 80.0 24.3 18.3 2024 03 11 01 04.55 +71 50.8 2.451 2.433 77.3 23.5 18.5 2024 03 16 01 16.56 +71 19.0 2.566 2.494 74.6 22.6 18.7 2024 03 21 01 27.75 +70 55.3 2.679 2.554 72.1 21.8 18.9 2024 03 26 01 38.33 +70 38.8 2.789 2.615 69.6 21.0 19.1 2024 03 31 01 48.46 +70 28.7 2.896 2.674 67.3 20.2 19.2 2024 04 05 01 58.25 +70 24.3 3.000 2.734 65.1 19.4 19.4 2024 04 10 02 07.78 +70 25.2 3.100 2.793 63.1 18.6 19.5 2024 04 15 02 17.12 +70 30.8 3.197 2.852 61.2 17.9 19.7 2024 04 20 02 26.30 +70 40.6 3.290 2.911 59.4 17.3 19.8 2024 04 25 02 35.36 +70 54.3 3.379 2.969 57.9 16.7 19.9 2024 04 30 02 44.35 +71 11.5 3.464 3.027 56.5 16.1 20.0 2024 05 05 02 53.29 +71 32.0 3.545 3.085 55.3 15.6 20.2 2024 05 10 03 02.21 +71 55.5 3.622 3.142 54.3 15.1 20.3 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 December 12 (CBET 5322) Daniel W. E. Green