Electronic Telegram No. 5181 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 S4 (LEMMON) An apparently asteroidal object discovered on CCD images taken on Sept. 19 UT with the 1.5-m reflector at Mt. Lemmon (discovery observations tabulated below) has been found to show cometary appearance by CCD astrometrists elsewhere after it was posted to the Minor Planet Center's PCCP webpage. 2022 UT R.A. (2000) Decl. Mag. Sept.19.48802 2 52 09.09 +29 53 44.2 20.6 19.49273 2 52 08.99 +29 53 42.8 20.5 19.49744 2 52 08.87 +29 53 42.5 20.5 19.50215 2 52 08.77 +29 53 41.3 20.3 R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports that four 45-s w-band survey images obtained on Sept. 22.5 UT with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala show a condensed coma of size 1".5 (full-width-at-half-maximum in 1".2 seeing with no apparent tail (independent discovery). Weryk later found pre-discovery Pan-STARRS2 exposures taken (as above) on Aug. 26.5 that show a condensed comet of size 1".7 (FWHM) and mag 21 in 1".2 seeing, again with no tail. Ten stacked 120-s exposures taken remotely on Sept. 24.45-24.46 UT by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.43-m f/6.8 astrograph located at Mayhill, NM, USA, showed a stellar appearance; the magnitude was 20.3 as measured within a circular aperture of radius 5".7. L. Buzzi, Varese, Italy, writes that eighty stacked 60-s exposures taken in good conditions with a 0.84-m f/3.5 reflector on Oct. 4.1 (measured by Buzzi and A. Aletti) shows an essentially stellar appearance but with an apparent slight asymmetry toward the northeast/southwest. M. Jaeger reports that twenty-seven 100-s exposures images taken on Oct. 17.9 with a 0.41-m f/3.2 reflector at Oed, Austria, show a 10" coma of total mag 19.9; he has posted an image at the "ICQ Comet Observations" Facebook page. The available astrometry appears on MPEC 2022-U170. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 85 observations spanning 2022 Aug. 26-Oct. 21 (mean residual 0".3). These suggest that the comet will pass 1.08 AU from Jupiter in 2023 July. Nakano cautions about the emphasis of the single night of astrometry from Aug. 26 on the orbit, with a gap of more than seven weeks until the next observations. T = 2024 July 18.32788 TT Peri. = 268.36024 Node = 220.15643 2000.0 q = 2.7671362 AU Incl. = 101.02673 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. 2022 09 18 02 52.76 +29 58.6 6.117 6.732 124.1 7.1 20.6 2022 09 28 02 48.19 +29 22.4 5.917 6.660 134.7 6.1 20.4 2022 10 08 02 42.57 +28 36.7 5.741 6.588 145.4 4.9 20.3 2022 10 18 02 36.09 +27 41.3 5.593 6.516 156.0 3.6 20.2 2022 10 28 02 29.04 +26 36.5 5.477 6.444 165.5 2.2 20.2 2022 11 07 02 21.74 +25 23.4 5.395 6.371 169.0 1.7 20.1 2022 11 17 02 14.58 +24 04.3 5.350 6.299 162.2 2.7 20.0 2022 11 27 02 07.91 +22 41.7 5.339 6.226 151.7 4.3 20.0 2022 12 07 02 02.04 +21 18.9 5.361 6.153 140.5 5.8 20.0 2022 12 17 01 57.21 +19 58.6 5.411 6.080 129.1 7.2 19.9 2022 12 27 01 53.57 +18 43.3 5.484 6.008 117.9 8.3 19.9 2023 01 06 01 51.19 +17 35.0 5.574 5.935 106.9 9.1 19.9 2023 01 16 01 50.08 +16 34.6 5.674 5.862 96.2 9.6 19.9 2023 01 26 01 50.19 +15 42.5 5.778 5.789 85.7 9.8 19.9 2023 02 05 01 51.43 +14 58.6 5.880 5.716 75.6 9.6 19.9 2023 02 15 01 53.69 +14 22.2 5.975 5.642 65.8 9.2 19.9 2023 02 25 01 56.88 +13 52.5 6.058 5.569 56.3 8.5 19.9 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2022 CBAT 2022 October 22 (CBET 5181) Daniel W. E. Green