Electronic Telegram No. 5547 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/2025 H1 = P/2003 QX_29 (NEAT) On 2025 Jan. 17, S. Deen (Simi Valley, CA, USA) reported that he had tentatively identified a single observation of comet P/2003 QX_29 (cf. IAUC 8192) obtained on 2024 Sept. 1.97 UT with the 4-m reflector (+ DECam) at Cerro Tololo, with the comet showing a condensed coma of size about 1".2 (full- width-at-half-maximum) and a tail about 3' long toward p.a. 105 degrees; the Minor Planet Center inadvertently published this single observation on MPEC 2025-C143 without any other confirming observations available. Deen also identified (and reported on Jan. 17) an image of the comet from 2004 July 14.52 at magnitude r = 23.9 that had been obtained with the Subaru 8.2-m telescope at Mauna Kea (there had previously been no known observations after 2003 Oct. 20). 2004 UT R.A. (2000) Decl. Mag. July 14.51941 1 15 54.05 +19 45 14.2 23.9 2024 UT R.A. (2000) Decl. Mag. Sept. 1.99674 16 16 49.48 -22 29 27.6 22.0 On 2025 Apr. 23, G. J. Leonard (University of Arizona) reported a possible new comet discovery on survey CCD images obtained with the Mt. Lemmon 1.5-m reflector (discovery observations tabulated below); Leonard described the object as having a moderately condensed coma about 8" across with no obvious tail in four co-added 30-s images. 2025 UT R.A. (2000) Decl. Mag. Observer Apr. 23.45344 20 09 53.29 -15 16 32.4 20.3 Leonard 23.45864 20 09 53.43 -15 16 31.1 21.1 " 23.46383 20 09 53.60 -15 16 29.6 20.3 " 23.46903 20 09 53.73 -15 16 28.6 20.3 " After Leonard's object was apparently posted to the MPC's PCCP webpage (under the preliminary designation CD876E2), W. H. Ryan reported that CCD images obtained on 2025 Apr. 24.45-24.47 UT with the 2.4-m f/8.9 Ritchey-Chretien reflector at Magdalena Ridge Observatory in New Mexico show a slightly ellipical, condensed coma of size 3" and mag 20.2-20.3, with a faint tail about 8" long spanning p.a. 244-259 degrees. These observations were identified at the MPC as being observations of P/2003 QX_29, and the MPC also identified three observations of this comet at mag 21.4-22.0 in its "isolated tracklet file" from 2024 July 1 that were obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala. Additional astrometry appears on MPEC 2025-H183. The residuals for the recovery observations are +17'.4 in R.A. and +7'.0 in Decl. from the prediction in NK 1112 and in the ICQ's 2025 Comet Handbook (from orbit an orbit in the ICQ's 2004 Comet Handbook), with a corresponding correction of Delta(T) = -2.25 days. The following linked orbital elements by S. Nakano (Central Bureau) are from 125 observations spanning 2002 June 11, 2003 Aug. 23-Oct. 20, 2004 July 14, and 2024 July 1-2025 Apr. 27 (mean residual 0".6). The comet will pass 1.59 AU from Saturn on 2032 Apr. 10 UT. Epoch = 2002 Oct. 13.0 TT T = 2002 Oct. 27.20171 TT Peri. = 37.34641 e = 0.4715670 Node = 264.59035 2000.0 q = 4.2399277 AU Incl. = 11.39705 a = 8.0235859 AU n = 0.04336619 P = 22.73 years Epoch = 2025 July 24.0 TT T = 2025 Aug. 5.07573 TT Peri. = 37.73967 e = 0.4711490 Node = 264.48500 2000.0 q = 4.2295020 AU Incl. = 11.39966 a = 7.9975302 AU n = 0.04357830 P = 22.62 years Epoch = 2047 Nov. 26.0 TT T = 2047 Nov. 30.97708 TT Peri. = 37.01165 e = 0.4703144 Node = 264.04368 2000.0 q = 4.1952693 AU Incl. = 11.47389 a = 7.9203005 AU n = 0.04421724 P = 22.29 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 9.5 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 03 26 19 50.91 -17 18.9 4.555 4.297 68.8 12.5 19.1 2025 04 05 19 58.60 -16 35.6 4.404 4.287 76.8 13.1 19.0 2025 04 15 20 05.21 -15 52.4 4.250 4.278 84.9 13.5 19.0 2025 04 25 20 10.64 -15 10.1 4.094 4.270 93.2 13.6 18.9 2025 05 05 20 14.77 -14 29.6 3.941 4.262 101.7 13.4 18.8 2025 05 15 20 17.50 -13 51.8 3.794 4.256 110.5 12.9 18.7 2025 05 25 20 18.78 -13 17.5 3.656 4.250 119.7 12.0 18.6 2025 06 04 20 18.57 -12 47.6 3.532 4.244 129.1 10.7 18.5 2025 06 14 20 16.91 -12 22.7 3.424 4.240 138.7 9.1 18.4 2025 06 24 20 13.95 -12 03.2 3.336 4.236 148.6 7.2 18.4 2025 07 04 20 09.90 -11 49.2 3.272 4.234 158.4 5.1 18.3 2025 07 14 20 05.11 -11 40.7 3.234 4.231 167.3 3.0 18.3 2025 07 24 19 59.98 -11 36.9 3.223 4.230 171.1 2.1 18.3 2025 08 03 19 54.97 -11 37.2 3.241 4.230 164.9 3.6 18.3 2025 08 13 19 50.53 -11 40.4 3.287 4.230 155.5 5.7 18.3 2025 08 23 19 47.05 -11 45.5 3.357 4.231 145.6 7.8 18.4 2025 09 02 19 44.82 -11 51.1 3.451 4.233 135.7 9.6 18.5 2025 09 12 19 44.03 -11 56.1 3.564 4.235 126.1 11.1 18.5 2025 09 22 19 44.77 -11 59.5 3.692 4.238 116.7 12.2 18.6 2025 10 02 19 47.02 -12 00.4 3.832 4.243 107.5 13.0 18.7 2025 10 12 19 50.73 -11 57.9 3.980 4.247 98.7 13.4 18.8 2025 10 22 19 55.79 -11 51.4 4.132 4.253 90.1 13.5 18.9 2025 11 01 20 02.05 -11 40.4 4.286 4.259 81.8 13.3 19.0 2025 11 11 20 09.38 -11 24.4 4.437 4.267 73.7 12.9 19.0 2025 11 21 20 17.62 -11 03.3 4.583 4.274 65.8 12.2 19.1 2025 12 01 20 26.64 -10 36.7 4.722 4.283 58.1 11.3 19.2 2025 12 11 20 36.28 -10 04.6 4.851 4.292 50.5 10.2 19.3 2026 04 30 22 59.10 +04 01.8 5.038 4.495 52.4 10.2 19.5 2026 05 10 23 06.62 +05 09.5 4.937 4.514 59.8 11.1 19.5 2026 05 20 23 13.37 +06 14.7 4.827 4.533 67.3 11.9 19.5 2026 05 30 23 19.25 +07 16.4 4.710 4.554 75.0 12.4 19.4 2026 06 09 23 24.18 +08 13.9 4.587 4.574 82.9 12.7 19.4 2026 06 19 23 28.04 +09 06.2 4.463 4.596 91.1 12.8 19.4 2026 06 29 23 30.75 +09 52.3 4.340 4.617 99.5 12.5 19.3 2026 07 09 23 32.25 +10 31.1 4.221 4.639 108.1 12.0 19.3 2026 07 19 23 32.49 +11 01.5 4.110 4.662 117.1 11.2 19.3 2026 07 29 23 31.47 +11 22.5 4.011 4.685 126.3 10.1 19.2 2026 08 08 23 29.29 +11 33.3 3.929 4.709 135.8 8.6 19.2 2026 08 18 23 26.07 +11 33.5 3.866 4.733 145.2 7.0 19.2 2026 08 28 23 22.07 +11 23.2 3.826 4.757 154.4 5.3 19.2 2026 09 07 23 17.60 +11 03.3 3.812 4.782 162.2 3.7 19.2 2026 09 17 23 13.01 +10 35.4 3.827 4.807 165.6 3.0 19.2 2026 09 27 23 08.69 +10 01.9 3.870 4.833 161.8 3.7 19.3 2026 10 07 23 04.98 +09 25.6 3.941 4.858 153.8 5.2 19.3 2026 10 17 23 02.17 +08 49.3 4.039 4.885 144.5 6.8 19.4 2026 10 27 23 00.48 +08 15.7 4.161 4.911 134.7 8.3 19.5 2026 11 06 23 00.01 +07 46.9 4.303 4.938 125.0 9.5 19.6 2026 11 16 23 00.80 +07 24.6 4.461 4.966 115.4 10.4 19.7 2026 11 26 23 02.82 +07 09.7 4.631 4.993 105.9 11.0 19.8 2026 12 06 23 06.00 +07 02.8 4.809 5.021 96.7 11.2 19.9 2026 12 16 23 10.24 +07 04.0 4.991 5.049 87.8 11.2 20.0 2026 12 26 23 15.42 +07 13.0 5.172 5.077 79.0 11.0 20.1 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 April 28 (CBET 5547) Daniel W. E. Green