Electronic Telegram No. 5112 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 F1 (ATLAS) A new comet discovered on CCD images taken on Mar. 30.3 UT with a 0.5-m f/2 Wright-Schmidt reflector at Rio Hurtado, Chile, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program, reported by L. Denneau to the Minor Planet Center, was noted by John Tonry as being slightly diffuse in the discovery exposures (which are tabulated below), with a coma size of 5".5 (full-width-at-half-maximum) in 3".9 seeing. 2022 UT R.A. (2000) Decl. Mag. Mar. 30.29854 18 23 12.63 -83 35 51.0 18.6 30.30125 18 23 12.66 -83 35 51.9 18.7 30.31076 18 23 14.70 -83 35 56.1 18.6 30.32206 18 23 16.63 -83 36 01.7 18.9 30.32341 18 23 17.20 -83 36 01.5 18.6 30.32525 18 23 17.27 -83 36 02.7 18.9 30.33162 18 23 18.14 -83 36 05.5 18.7 30.33658 18 23 18.81 -83 36 10.1 18.7 30.33932 18 23 20.32 -83 36 10.4 18.8 After the comet was posted on the MPC's PCCP webpage, other CCD astrometrists have commented on the cometary appearance. F. D. Romanov writes that three stacked 300-s exposures taken remotely on Mar. 31.6 UT with an iTelescope 0.50-m f/6.8 reflector at Siding Spring Observatory show a condensed coma 12" in diameter and a faint straight tail 15" long in p.a. 230 degrees; the total magnitude was 18.6--18.7 (Gaia DR2 band) in an aperture of radius 5". Five stacked 120-s exposures taken remotely by H. Sato (Tokyo, Japan) on Mar. 31.8 using a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, show a strongly condensed coma 10" in diameter with no tail; the magnitude was 18.5 as measured within a circular aperture of radius 6".5. E. Bryssinck, Kruibeke, Belgium, has measured twenty stacked 90-s luminance-filtered exposures obtained remotely by a large group of observers on Apr. 2.4 using a "Telescope Live" 0.61-m f/6.5 astrograph located at El Sauce, Chile, which show a condensed coma about 9" in diameter with magnitude 18.7-19.3 in an aperture radius of 5."5. C. Jacques, Belo Horizonte, MG, Brazil, find a 12" condensed coma with no tail in one-hundred stacked 30-s exposures taken on Apr. 4.1 with a 0.45-m f/2.9 reflector at the SONEAR Observatory, Oliveria. The available astrometry appears on MPEC 2022-G82. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 30 observations spanning 2022 Mar. 30-Apr. 5 (mean residual 0".5); these suggest that the comet will pass 1.46 AU from Saturn in 2025 August. T = 2022 Sept. 4.00477 TT Peri. = 281.10642 Node = 350.73296 2000.0 q = 5.9487809 AU Incl. = 57.98012 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 8.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Nag, 2022 03 02 17 05.10 -79 48.0 6.149 6.091 82.0 9.3 18.7 2022 03 12 17 31.04 -81 12.8 6.058 6.077 86.4 9.4 18.7 2022 03 22 17 58.73 -82 33.0 5.970 6.063 90.6 9.5 18.6 2022 04 01 18 28.39 -83 48.3 5.886 6.049 94.6 9.5 18.6 2022 04 11 19 00.22 -84 58.2 5.808 6.037 98.4 9.4 18.6 2022 04 21 19 34.56 -86 02.6 5.736 6.025 102.0 9.4 18.5 2022 05 01 20 11.84 -87 01.6 5.672 6.015 105.1 9.3 18.5 2022 05 11 20 52.73 -87 55.4 5.617 6.005 107.9 9.2 18.5 2022 05 21 21 39.78 -88 44.6 5.572 5.996 110.1 9.1 18.5 2022 05 31 22 49.91 -89 29.9 5.536 5.987 111.8 9.0 18.4 2022 06 10 09 08.86 -89 44.9 5.512 5.980 112.8 9.0 18.4 2022 06 20 11 03.88 -89 03.9 5.499 5.973 113.2 9.0 18.4 2022 06 30 11 58.43 -88 21.5 5.497 5.967 112.9 9.0 18.4 2022 07 10 12 46.00 -87 37.4 5.506 5.962 112.0 9.1 18.4 2022 07 20 13 30.22 -86 50.3 5.527 5.958 110.4 9.2 18.4 2022 07 30 14 11.82 -85 59.3 5.559 5.954 108.2 9.3 18.4 2022 08 09 14 50.96 -85 03.6 5.601 5.952 105.4 9.5 18.4 2022 08 19 15 27.65 -84 03.1 5.652 5.950 102.3 9.6 18.5 2022 08 29 16 02.02 -82 57.5 5.712 5.949 98.7 9.7 18.5 2022 09 08 16 34.25 -81 46.9 5.780 5.949 94.7 9.7 18.5 2022 09 18 17 04.46 -80 31.7 5.854 5.950 90.6 9.7 18.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2022 CBAT 2022 April 6 (CBET 5112) Daniel W. E. Green