Electronic Telegram No. 5070 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/2021 U5 (CATALINA) An apparently asteroidal object discovered on CCD images obtained on Oct. 29 by A. R. Gibbs with the Catalina Sky Survey's 0.68-m Schmidt telescope (discovery observations tabulated below) has been shown to have cometary appearance by CCD astrometrists elsewhere after it was posted on the Minor Planet Center's PCCP webpage. 2021 UT R.A. (2000) Decl. Mag. Observer Oct. 29.49132 8 58 37.45 -20 02 23.4 19.1 Gibbs 29.49595 8 58 37.96 -20 02 27.0 18.8 " 29.50057 8 58 38.31 -20 02 28.2 18.7 " 29.50519 8 58 38.69 -20 02 30.4 19.2 " One-hundred stacked 15-s exposures taken on Nov. 6.2 UT by L. Buzzi at Varese, Italy, with a 0.84-m f/3.5 reflector (and measured by A. Aletti) show a condensed coma 6" wide (and mag 18.8) with a tail 10" long in PA 290 degrees. Fourteen stacked 60-s exposures taken remotely on Nov. 8.5 by H. Sato (Tokyo, Japan) with a 0.43-m f/6.8 astrograph located near Mayhill, NM, USA, show a strongly condensed coma 12" in diameter with a wide tail 15" long toward p.a. 270 degrees; the magnitude was 18.6 as measured within a circular aperture of radius 7".6. The available astrometry appears on MPEC 2021-V199. The following parabolic orbital elements by S. Nakano (CBAT) are from 56 observations spanning Oct. 29-Nov. 9 (mean residual 0".5) and indicate that the comet passed 2.71 AU from Uranus in 2013 Sept. T = 2022 Jan. 25.64121 TT Peri. = 320.98936 Node = 182.92234 2000.0 q = 2.3712769 AU Incl. = 39.02844 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. 2021 11 02 09 03.93 -20 39.4 2.588 2.551 76.7 22.3 18.3 2021 11 12 09 18.47 -22 23.2 2.467 2.512 81.1 22.9 18.2 2021 11 22 09 32.02 -24 01.9 2.347 2.478 85.8 23.4 18.0 2021 12 02 09 44.37 -25 31.9 2.228 2.448 90.7 23.7 17.9 2021 12 12 09 55.28 -26 48.9 2.112 2.423 96.1 23.8 17.7 2021 12 22 10 04.51 -27 47.7 1.998 2.403 101.9 23.6 17.5 2022 01 01 10 11.84 -28 22.7 1.888 2.387 108.3 23.0 17.4 2022 01 11 10 17.07 -28 27.0 1.784 2.377 115.3 22.0 17.3 2022 01 21 10 20.20 -27 53.4 1.689 2.372 122.8 20.4 17.1 2022 01 31 10 21.36 -26 35.2 1.607 2.372 130.9 18.3 17.0 2022 02 10 10 20.92 -24 27.4 1.541 2.377 139.3 15.7 16.9 2022 02 20 10 19.55 -21 30.0 1.495 2.388 147.3 12.9 16.9 2022 03 02 10 18.03 -17 49.5 1.476 2.404 153.5 10.6 16.9 2022 03 12 10 17.18 -13 39.8 1.485 2.425 155.5 9.8 16.9 2022 03 22 10 17.67 -09 20.4 1.525 2.450 152.1 11.0 17.0 2022 04 01 10 19.88 -05 10.5 1.595 2.480 145.0 13.4 17.2 2022 04 11 10 24.01 -01 25.2 1.692 2.515 136.5 15.9 17.3 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2021 CBAT 2021 November 10 (CBET 5070) Daniel W. E. Green