Electronic Telegram No. 5212 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 Y2 (LEMMON) [Editor's note: this text replaces that on CBET 5211 (Mauna Kea date).] An apparently asteroidal object discovered with the Mt. Lemmon Survey's 1.5-m reflector on 2022 Dec. 24 (discovery observations tabulated below) has been found to show cometary appearance by CCD astrometrists elsewhere after the object was posted on the Minor Planet Center's PCCP webpage. 2022 UT R.A. (2000) Decl. Mag. Dec. 24.46872 11 12 42.34 +23 44 17.4 20.0 24.46963 11 12 42.23 +23 44 18.5 20.3 24.47385 11 12 41.80 +23 44 24.4 20.2 24.47478 11 12 41.73 +23 44 25.7 20.6 24.47900 11 12 41.30 +23 44 31.2 20.3 24.47991 11 12 41.20 +23 44 32.7 20.4 24.48414 11 12 40.74 +23 44 38.2 20.1 24.48507 11 12 40.70 +23 44 39.4 20.2 Twelve stacked 60-s exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) on 2023 Jan. 27.21 UT using an iTelescope 0.43-m f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) show a strongly condensed coma 8" in diameter with no tail; the magnitude was 18.8 as measured within a circular aperture of radius 5".7. Sato had previously found the comet to show only a stellar appearance on twenty stacked 60-s exposures taken remotely on 2022 Dec. 26.4 UT with a 0.61-m f/6.5 astrograph located at the Sierra Remote Observatory near Auberry, CA, USA (when the magnitude was 20.2 as measured within a circular aperture of radius 3".8). Y. Ramanjooloo reports that multiple exposures taken on 2022 Dec. 31.53 with the University of Hawaii 2.2-m reflector at Mauna Kea show a broad, faint tail 5".5 long and 3".3 wide in p.a. 235 degrees (the tail spanning p.a. 225-261 deg); the object's condensed head showed a size of about 2".1 (full-width-at-half-maximum) in the best image in 1".1 seeing. Two 15-s exposures taken with the same telescope on 2023 Jan. 2 show a very faint tail about 5" long extending towards p.a. 236 deg; the object's very condensed head showed a size of about 2".3 (FWHM) in 1".1 seeing. Fifty-eight 60-s exposures taken by L. Buzzi, Varese, Italy, with a 0.84-m f/3.5 reflector (and measured by Buzzi and A. Aletti) on 2023 Jan. 28.04-28.15 show a condensed coma 7" wide extended toward p.a. around 145 deg. Twenty-one stacked 60-s exposures taken by D. D. Balam, C. E. Spratt, P. Langill, and D. W. E. Green with the Dominion Astrophysical Observatory 1.82-m Plaskett telescope (+ SDSS g' filter) of the National Research Council of Canada on Jan. 30.30 clearly show a short fan- shaped tail extending 16" toward p.a. 130 deg; the head of the comet was measured to be 4".8 in size (FWHM) in 3".3 seeing. The available astrometry appear on MPEC 2023-B225. The following preliminary elliptical orbital elements by S. Nakano (Central Bureau) are from 109 observations spanning 2022 Dec. 24-2023 Jan. 30 (mean residual 0".6); the uncertainty on the orbital period is +/- 0.75 yr. The comet will pass 1.34 AU from Jupiter in 2023 Dec. and 2.03 AU from Saturn in 2025 Oct. No other observations were found in a search of archival astrometry. T = 2023 Mar. 22.62595 TT Peri. = 105.54693 e = 0.8705043 Node = 216.34714 2000.0 q = 2.5450110 AU Incl. = 165.90692 a = 19.6532405 AU n = 0.01131235 P = 87.127 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 14.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2022 10 28 11 38.22 +13 29.4 3.535 2.926 45.5 14.0 20.5 2022 11 07 11 39.38 +14 09.7 3.325 2.880 55.4 16.5 20.3 2022 11 17 11 39.16 +15 09.5 3.095 2.835 65.7 18.5 20.1 2022 11 27 11 36.98 +16 34.7 2.851 2.794 76.7 20.1 19.8 2022 12 07 11 32.00 +18 32.9 2.599 2.755 88.5 20.9 19.6 2022 12 17 11 23.02 +21 12.7 2.350 2.719 101.2 20.8 19.3 2022 12 27 11 08.32 +24 42.4 2.114 2.685 115.2 19.3 19.1 2023 01 06 10 45.54 +29 03.3 1.910 2.655 130.5 16.4 18.8 2023 01 16 10 11.96 +33 58.3 1.755 2.629 146.0 12.1 18.6 2023 01 26 09 26.09 +38 37.4 1.671 2.606 157.0 8.5 18.4 2023 02 05 08 31.08 +41 48.4 1.669 2.586 152.9 10.0 18.4 2023 02 15 07 35.95 +42 49.6 1.748 2.570 138.2 14.9 18.5 2023 02 25 06 49.84 +42 04.4 1.893 2.558 121.9 19.2 18.6 2023 03 07 06 16.00 +40 26.8 2.083 2.550 106.6 21.9 18.8 2023 03 17 05 52.97 +38 37.8 2.297 2.546 92.7 23.0 19.1 2023 03 27 05 38.07 +36 57.2 2.521 2.545 80.0 22.7 19.3 2023 04 06 05 28.89 +35 31.6 2.741 2.549 68.4 21.4 19.4 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 January 31 (CBET 5212) Daniel W. E. Green