Electronic Telegram No. 5011 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 P/2021 L6 = P/2017 S5 (ATLAS) M. Micheli reports the recovery of comet P/2017 S5 (cf. CBET 4434) on CCD images taken by H. H. Hsieh, S. Margheim, and L. Magill with the 8.1-m "Gemini South" telescope (astrometry tabulated below). Nothing was reported about the comet's appearance, but its faintness suggests stellar appearance. 2021 UT R.A. (2000) Decl. Mag. Observer June 9.07200 12 53 33.18 -15 45 44.6 24.0 Hsieh 9.07591 12 53 33.17 -15 45 43.7 24.7 " 9.07981 12 53 33.17 -15 45 42.7 24.2 " 9.08372 12 53 33.16 -15 45 41.3 24.1 " 12.99975 12 53 36.20 -15 31 08.0 24.8 " 13.00366 12 53 36.21 -15 31 07.2 24.8 " 13.00758 12 53 36.24 -15 31 06.5 24.9 " 13.01147 12 53 36.23 -15 31 05.6 24.4 " 13.01538 12 53 36.23 -15 31 04.7 24.4 " 13.01928 12 53 36.23 -15 31 03.9 24.7 " The residuals for the recovery observations are +107" in R.A. and -30" in Decl. from the prediction in NK 4193 and the ICQ's 2021 Comet Handbook, with a corresponding correction of Delta(T) = -0.25 day. The following linked orbital elements by S. Nakano (CBAT) are from 430 observations spanning 2017-2021 (mean residual 0".5). Epoch = 2017 July 26.0 TT T = 2017 July 28.03200 TT Peri. = 99.94600 e = 0.3130002 Node = 252.39285 2000.0 q = 2.1782501 AU Incl. = 11.84921 a = 3.1706708 AU n = 0.17457311 P = 5.65 years Epoch = 2023 Apr. 6.0 TT T = 2023 Mar. 19.34176 TT Peri. = 99.97922 e = 0.3148770 Node = 252.34973 2000.0 q = 2.1704996 AU Incl. = 11.85505 a = 3.1680439 AU n = 0.17479029 P = 5.64 years Epoch = 2028 Nov. 5.0 TT T = 2028 Oct. 31.67200 TT Peri. = 99.51663 e = 0.3155644 Node = 252.31817 2000.0 q = 2.1664430 AU Incl. = 11.86374 a = 3.1652984 AU n = 0.17501775 P = 5.63 years Epoch = 2034 June 7.0 TT T = 2034 June 16.34237 TT Peri. = 99.35382 e = 0.3171581 Node = 252.28479 2000.0 q = 2.1605116 AU Incl. = 11.86640 a = 3.1639996 AU n = 0.17512553 P = 5.63 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.5 and 2.5n = 10.0 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2022 02 10 17 22.20 -24 24.3 3.522 3.139 59.5 15.7 21.2 2022 03 02 17 47.24 -24 04.5 3.199 3.077 74.0 18.0 20.9 2022 03 22 18 08.12 -23 22.9 2.859 3.014 89.2 19.3 20.6 2022 04 11 18 23.09 -22 23.0 2.521 2.951 105.5 19.1 20.2 2022 05 01 18 30.13 -21 09.1 2.209 2.887 123.3 17.0 19.8 2022 05 21 18 27.54 -19 45.1 1.948 2.823 143.0 12.5 19.5 2022 06 10 18 15.44 -18 15.1 1.768 2.759 164.3 5.7 19.1 2022 06 30 17 57.84 -16 47.3 1.690 2.696 169.3 4.0 18.9 2022 07 20 17 42.14 -15 36.5 1.717 2.633 147.8 11.9 18.9 2022 08 09 17 34.94 -14 55.1 1.828 2.572 127.3 18.3 18.9 2022 08 29 17 38.75 -14 41.9 1.993 2.513 109.2 22.3 19.0 2022 09 18 17 52.94 -14 43.5 2.182 2.457 93.5 24.1 19.1 2022 10 08 18 15.64 -14 42.7 2.374 2.403 79.6 24.1 19.2 2022 10 28 18 44.90 -14 23.6 2.557 2.354 67.0 22.9 19.3 2022 11 17 19 19.04 -13 33.7 2.719 2.309 55.6 20.7 19.3 2022 12 07 19 56.60 -12 04.8 2.858 2.269 44.9 17.8 19.3 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2021 CBAT 2021 August 8 (CBET 5011) Daniel W. E. Green