Electronic Telegram No. 5439 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/2024 Q2 = P/2005 SB_216 (LONEOS) On Aug. 30, Martin Masek (Institute of Physics of the Czech Academy of Sciences) reported an apparent recovery of comet P/2005 SB_216 (cf. IAUC 8668) on CCD images obtained with a 0.25-m f/6.8 reflector (known as the "Fotometric Robotic Atmospheric Monitor") located at the site of the Cherenkov Telescope Array, La Palma, Spain, with two additional nights of astrometry coming later (as tabulated below). Masek notes that the object appears essentially stellar (though the head of the comet has a size around 4".9 full-width-at-half- maximum) in 3".5-4".2 seeing on the first night. 2024 UT R.A. (2000) Decl. Mag. Observer Aug. 30.13457 1 16 28.15 +15 46 14.5 19.6 Masek 30.16469 1 16 27.50 +15 46 20.0 19.6 " 30.19810 1 16 26.93 +15 46 24.8 19.8 " 30.99335 1 16 12.30 +15 48 28.8 19.5 " 31.05286 1 16 11.12 +15 48 37.5 19.6 " Sept. 1.04281 1 15 52.03 +15 51 08.0 19.5 " 1.09740 1 15 50.89 +15 51 16.1 19.6 " On Sept. 3, Michael S. P. Kelley (University of Maryland) reported the independent recovery of this comet in CCD observations obtained on a dozen nights last month (Aug. 2-29) with the 1.2-m Schmidt telescope at Palomar (+ ZTF camera), with additional observers G. Helou and T. A. Prince (and measuring by Kelley and F. J. Masci). The comet appeared essentially stellar with i and r magnitudes generally 20.0-20.5 and g magnitudes generally around 21. Two 30-s r-band images from Aug. 25.4 UT show the head as having a size of 3".0 (FWHM) in 2'.1 seeing with a limiting magnitude (5 sigma) of 20.5. The available astrometry appears on MPEC 2024-R78. The residuals for the recovery observations are +58" in R.A. and +56" in Decl. from the prediction on NK 1828 (and in the ICQ's 2024 Comet Handbook), with a corresponding correction of Delta(T) = -0.18 day. The following linked orbital elements by S. Nakano (Central Bureau) are from 503 observations spanning 2005 Sept. 23- 2024 Sept. 3 (mean residual 0".6; twenty-four observations were rejected). The comet will pass 0.57 AU from Jupiter on 2028 Feb. 13 UT. Epoch = 2007 Mar. 1.0 TT T = 2007 Feb. 11.39086 TT Peri. = 83.57784 e = 0.4633200 Node = 1.69902 2000.0 q = 3.8183352 AU Incl. = 24.09810 a = 7.1147330 AU n = 0.05193572 P = 18.98 years Epoch = 2025 Dec. 31.0 TT T = 2026 Jan. 14.11747 TT Peri. = 83.23281 e = 0.4673394 Node = 1.08097 2000.0 q = 3.8229405 AU Incl. = 24.10767 a = 7.1770663 AU n = 0.05126059 P = 19.23 years Epoch = 2043 May 31.0 TT T = 2043 May 30.95107 TT Peri. = 78.53509 e = 0.4483583 Node = 359.94664 2000.0 q = 3.7163480 AU Incl. = 24.91762 a = 6.7368873 AU n = 0.05636573 P = 17.49 years Epoch = 2060 Dec. 7.0 TT T = 2060 Dec. 3.10617 TT Peri. = 77.68354 e = 0.4536412 Node = 359.65938 2000.0 q = 3.7519378 AU Incl. = 24.84799 a = 6.8671687 AU n = 0.05476934 P = 18.00 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 11.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 08 18 01 19.17 +15 09.4 4.221 4.821 121.0 10.4 19.6 2024 08 28 01 17.09 +15 40.5 4.068 4.790 130.8 9.2 19.5 2024 09 07 01 13.68 +16 04.7 3.934 4.758 140.8 7.7 19.4 2024 09 17 01 09.08 +16 21.5 3.823 4.727 151.0 5.9 19.3 2024 09 27 01 03.53 +16 30.9 3.738 4.696 160.9 4.0 19.2 2024 10 07 00 57.34 +16 33.1 3.681 4.665 168.8 2.4 19.2 2024 10 17 00 50.98 +16 29.4 3.654 4.635 168.4 2.5 19.1 2024 10 27 00 44.88 +16 21.6 3.658 4.605 160.1 4.2 19.1 2024 11 06 00 39.49 +16 12.0 3.691 4.575 149.9 6.2 19.1 2024 11 16 00 35.20 +16 03.2 3.749 4.546 139.4 8.1 19.1 2024 11 26 00 32.26 +15 57.6 3.830 4.516 128.9 9.8 19.2 2024 12 06 00 30.82 +15 57.1 3.930 4.488 118.8 11.1 19.2 2024 12 16 00 30.95 +16 03.4 4.042 4.459 108.9 12.1 19.2 2024 12 26 00 32.61 +16 17.2 4.163 4.431 99.4 12.6 19.3 2025 01 05 00 35.72 +16 38.9 4.288 4.404 90.3 12.9 19.3 2025 01 15 00 40.17 +17 08.6 4.413 4.376 81.5 12.8 19.4 2025 01 25 00 45.83 +17 45.8 4.534 4.349 73.0 12.5 19.4 2025 02 04 00 52.59 +18 30.2 4.649 4.323 64.9 11.9 19.4 2025 02 14 01 00.30 +19 21.0 4.754 4.297 57.0 11.1 19.5 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 September 5 (CBET 5439) Daniel W. E. Green