Electronic Telegram No. 5680 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 R3 (PANSTARRS) Selected visual total-magnitude and coma-diameter estimates: Mar. 17.21 UT, 7.6, 8' (J. J. Gonzalez, Leon, Spain, 15x70 binoculars); 19.17, 8.8, 1'.2 (W. Hasubick, Buchloe, Germany, 44-cm reflector); 20.22, 8.5, 3' (V. Gonano, Udine, Italy, 20x80 binoculars); 24.20, 7.1, 6' (Gonzalez, 10x50 binoculars); 27.18, 7.3, 3' (Gonano); 30.14, 7.2, 4' (Gonano); Apr. 1.15, 7.0, 4' (Gonano); 4.16, 5.9, 3' (Gonzalez, 15x70 binoculars); 4.34 6.1, 2'.5 (M. Goiato, Aracatuba, Brasil, 20x100 binoculars; moonlight, comet altitude 5.5 deg; magnitude corrected for atmospheric extinction); 5.34, 6.0, 3' (W. Souza, Atibaia, Brazil, 10x42 binoculars); 6.15, 6.0, 3' (Gonano). Updated orbital elements by S. Nakano (Central Bureau) from 515 observations spanning 2025 Sept. 7-2026 Mar. 20 (mean residual 0".6), with corresponding "original" and "future" values of 1/a being +0.000318 and -0.000501 (+/- 0.000002) AU**-1, respectively. The comet passed 1.58 AU from Uranus on 2019 Nov. 23 UT. Epoch = 2026 Apr. 30.0 TT T = 2026 Apr. 19.89615 TT Peri. = 162.22446 e = 1.0003622 Node = 38.69471 2000.0 q = 0.4986378 AU Incl. = 124.73185 The light curve posited on CBET 5607 was followed closely until about r = 2.0 AU in January; since then the light curve has risen more steeply. Given the comet's instrinsic faintness, this may be another candidate for nucleus disruption near perihelion. The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 10.0 and 2.5n = 15 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2026 02 09 22 16.47 +17 34.0 2.231 1.523 34.5 21.5 14.5 2026 02 14 22 17.99 +17 32.6 2.187 1.442 31.6 21.0 14.1 2026 02 19 22 19.65 +17 35.5 2.134 1.359 29.2 20.8 13.6 2026 02 24 22 21.44 +17 42.1 2.070 1.276 27.4 20.9 13.2 2026 03 01 22 23.33 +17 52.4 1.996 1.191 26.3 21.6 12.6 2026 03 06 22 25.35 +18 05.8 1.910 1.106 25.9 23.1 12.1 2026 03 11 22 27.54 +18 22.1 1.812 1.020 26.2 25.5 11.4 2026 03 16 22 29.99 +18 40.8 1.701 0.934 27.2 29.1 10.7 2026 03 21 22 32.90 +19 00.9 1.576 0.848 28.6 34.2 9.9 2026 03 26 22 36.66 +19 21.1 1.437 0.765 30.3 41.2 9.0 2026 03 31 22 42.06 +19 39.0 1.282 0.685 32.0 50.6 8.1 2026 04 05 22 50.71 +19 49.7 1.112 0.613 33.2 63.4 7.0 2026 04 10 23 06.02 +19 43.6 0.930 0.553 33.0 80.7 6.0 2026 04 15 23 34.94 +18 56.2 0.745 0.513 29.7 104.3 5.0 2026 04 20 00 29.71 +16 23.6 0.584 0.499 20.1 136.1 4.3 2026 04 25 01 58.76 +10 16.7 0.494 0.514 3.7 172.8 4.1 2026 04 30 03 36.21 +01 53.5 0.520 0.555 21.2 139.1 4.7 2026 05 05 04 45.82 -04 06.0 0.638 0.615 35.7 107.1 5.9 2026 05 10 05 27.67 -07 13.1 0.797 0.688 42.8 85.3 7.1 2026 05 15 05 53.34 -08 46.9 0.968 0.768 45.6 70.1 8.2 2026 05 20 06 10.33 -09 36.8 1.138 0.852 46.2 59.1 9.2 2026 05 25 06 22.52 -10 06.0 1.302 0.937 45.7 50.6 10.1 2026 05 30 06 31.88 -10 25.4 1.458 1.023 44.5 44.0 11.0 2026 06 04 06 39.48 -10 40.6 1.606 1.109 43.1 38.7 11.7 2026 06 09 06 45.94 -10 54.3 1.746 1.195 41.6 34.3 12.4 2026 06 14 06 51.60 -11 08.5 1.878 1.279 40.0 30.7 13.0 2026 06 19 06 56.70 -11 23.9 2.000 1.363 38.6 27.7 13.5 2026 06 24 07 01.35 -11 41.1 2.115 1.445 37.3 25.2 14.0 2026 06 29 07 05.65 -12 00.5 2.222 1.526 36.3 23.2 14.5 2026 07 04 07 09.65 -12 22.2 2.320 1.607 35.6 21.6 14.9 2026 07 09 07 13.38 -12 46.4 2.411 1.686 35.2 20.3 15.3 2026 07 14 07 16.87 -13 13.1 2.495 1.764 35.2 19.4 15.7 2026 07 19 07 20.13 -13 42.6 2.571 1.841 35.5 18.7 16.0 2026 07 24 07 23.15 -14 14.6 2.639 1.917 36.3 18.3 16.3 2026 07 29 07 25.93 -14 49.3 2.701 1.992 37.4 18.0 16.6 2026 08 03 07 28.46 -15 26.6 2.756 2.066 38.9 17.9 16.9 2026 08 08 07 30.74 -16 06.5 2.804 2.140 40.7 18.0 17.2 2026 08 13 07 32.74 -16 49.1 2.846 2.212 42.8 18.1 17.4 2026 08 18 07 34.45 -17 34.3 2.882 2.284 45.2 18.3 17.7 2026 08 23 07 35.84 -18 22.0 2.912 2.354 47.8 18.5 17.9 2026 08 28 07 36.88 -19 12.2 2.936 2.425 50.6 18.8 18.1 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 April 6 (CBET 5680) Daniel W. E. Green