Electronic Telegram No. 5598 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/2025 O2 (MAPS) Alain Maury, San Pedro de Atacama, Chile, reports the discovery of a comet as a slightly fuzzy object on images obtained on July 25 UT with a 28-cm Celestron RASA Schmidt astrograph in the course of the MAPS survey (cf. CBET 5567), noting that the head showed a size of 5".2 (full-width-at-half-maximum) in 3".5 seeing with a slight elongation. The discovery observations are tabulated below. 2025 UT R.A. (2000) Decl. Mag. July 25.39965 3 41 11.97 -17 14 38.9 18.8 25.40596 3 41 11.59 -17 14 45.4 18.8 25.41225 3 41 11.27 -17 14 51.2 18.8 Other reports have been received as a result of the comet being placed on the Minor Planet Center's PCCP webpage. Forty stacked 30-s CCD exposures taken remotely by H. Sato (Tokyo, Japan) with a 0.51-m f/6.8 astrograph located at Rio Hurtado, Chile, on Aug. 10.3 UT show only a stellar appearance; the magnitude was 20.2 as measured within a circular aperture of radius 2".2. A. Aletti, Varese, Italy, writes that two-hundred stacked 300-s CMOS exposures taken on Aug. 22.04-22.08 by F. Bellini, L. Buzzi, G. Galli, and himself with a 0.36-m f/8.6 reflector at Hakos, Namibia, show a condensed 6" coma elongated toward p.a. 270 degrees. R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports that four 45-s w-band survey images taken on Aug. 27.6 with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala in 1".2-1".5 seeing show a diffuse coma of size 2".4 (FWHM) and a broad tail 6" long spanning p.a. 270-360 degrees. The available astrometry appears on MPEC 2025-Q231. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 84 observations spanning July 25-Aug. 29 (mean residual 0".6). The comet passed 3.62 AU from Jupiter on 2025 Feb. 8 UT. T = 2025 May 23.84028 TT Peri. = 280.29028 Node = 332.30391 2000.0 q = 2.2894282 AU Incl. = 134.54866 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 14.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 09 02 02 27.62 -29 12.3 1.857 2.557 123.6 19.2 18.6 2025 09 07 02 09.94 -30 55.5 1.820 2.582 129.6 17.5 18.6 2025 09 12 01 50.29 -32 28.7 1.797 2.608 135.0 15.8 18.6 2025 09 17 01 29.01 -33 46.2 1.790 2.635 139.3 14.4 18.6 2025 09 22 01 06.69 -34 43.2 1.799 2.662 141.9 13.4 18.7 2025 09 27 00 44.07 -35 16.8 1.825 2.690 142.5 13.1 18.7 2025 10 02 00 21.95 -35 26.2 1.867 2.719 141.0 13.4 18.8 2025 10 07 00 01.06 -35 13.4 1.925 2.749 137.8 14.1 18.9 2025 10 12 23 41.92 -34 41.8 1.998 2.779 133.3 15.1 19.1 2025 10 17 23 24.86 -33 55.6 2.084 2.810 128.1 16.2 19.2 2025 10 22 23 09.98 -32 59.1 2.181 2.842 122.5 17.2 19.3 2025 10 27 22 57.25 -31 55.9 2.287 2.874 116.7 18.0 19.5 2025 11 01 22 46.53 -30 49.2 2.400 2.907 110.9 18.6 19.6 2025 11 06 22 37.62 -29 41.0 2.520 2.940 105.2 19.0 19.8 2025 11 11 22 30.31 -28 33.1 2.644 2.973 99.5 19.2 19.9 2025 11 16 22 24.41 -27 26.3 2.772 3.007 94.0 19.2 20.0 2025 11 21 22 19.73 -26 21.3 2.901 3.042 88.6 18.9 20.2 2025 11 26 22 16.10 -25 18.4 3.031 3.077 83.3 18.6 20.3 2025 12 01 22 13.37 -24 17.7 3.162 3.112 78.1 18.1 20.4 2025 12 06 22 11.41 -23 19.2 3.290 3.148 73.0 17.4 20.6 2025 12 11 22 10.11 -22 22.9 3.418 3.184 68.1 16.7 20.7 2025 12 16 22 09.37 -21 28.7 3.542 3.220 63.2 15.8 20.8 2025 12 21 22 09.12 -20 36.4 3.663 3.256 58.3 14.9 20.9 2025 12 26 22 09.28 -19 45.8 3.781 3.293 53.6 13.9 21.0 2025 12 31 22 09.78 -18 56.8 3.894 3.330 48.9 12.9 21.1 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 September 1 (CBET 5598) Daniel W. E. Green