Electronic Telegram No. 5594 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 A6 (LEMMON) This comet (cf. CBET 5508) has had a notable outburst in brightness as it appears now in the morning sky after being hidden by the sun's glare for several months. H. Sato (Bunkyo-ku, Tokyo, Japan) obtained CCD exposures on Aug. 11.49 UT with a 0.51-m f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) that show a strongly condensed coma 20" in diameter; the magnitude was measured as 14.5 within a circular aperture of radius 11".5. M. Mattiazzo (Swan Hill, Vic., Australia) reports that twelve 30-s CMOS exposures taken on Aug. 12.48 with a 0.50-m f/3 telescope at Beryl Junction show a 1' coma of magnitude 13.9. K. Kadota (Ageo, Japan) obtained CCD images with a 0.25-m f/5 reflector on Aug. 14.8 that reveal a total magnitude of 13.2. Eleven 50-s exposures taken on Aug. 19.08 by M. Jaeger and G. Rhemann indicate a total magnitude near 11. The images posted at the "ICQ Comet Observations" forum on Facebook show a round coma and no obvious tail. The following updated orbital elements by S. Nakano (Central Bureau) are from 117 observations spanning 2024 Nov. 12-2025 Aug. 14 (mean residual 0".4), with corresponding "original" and "future" values of 1/a being +0.008193 and +0.009092 (+/- 0.000007) AU**-1, respectively. The comet passed 2.33 AU from Jupiter on 2025 Apr. 16 and will pass 0.60 AU from the earth on 2025 Oct. 21 UT. Epoch = 2025 Nov. 21.0 TT T = 2025 Nov. 8.53978 TT Peri. = 132.97025 e = 0.9956364 Node = 108.09813 2000.0 q = 0.5298877 AU Incl. = 143.66289 The following ephemeris by the undersigned from the above orbital elements cautiously uses photometric power-law parameters H = 10.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 08 13 07 30.62 +29 31.4 2.571 1.784 31.3 17.1 14.1 2025 08 18 07 37.12 +30 01.8 2.438 1.707 34.8 19.8 13.8 2025 08 23 07 44.12 +30 36.3 2.299 1.630 38.2 22.6 13.5 2025 08 28 07 51.75 +31 15.8 2.154 1.551 41.6 25.6 13.2 2025 09 02 08 00.21 +32 01.4 2.003 1.472 44.9 28.9 12.9 2025 09 07 08 09.79 +32 54.6 1.846 1.392 48.1 32.6 12.5 2025 09 12 08 20.93 +33 57.1 1.684 1.310 51.0 36.7 12.1 2025 09 17 08 34.33 +35 11.1 1.518 1.228 53.7 41.3 11.6 2025 09 22 08 51.13 +36 38.7 1.350 1.146 56.0 46.6 11.1 2025 09 27 09 13.23 +38 21.1 1.180 1.062 57.6 52.8 10.6 2025 10 02 09 43.98 +40 13.9 1.013 0.979 58.2 60.3 10.0 2025 10 07 10 28.96 +41 55.1 0.855 0.897 57.2 69.5 9.3 2025 10 12 11 35.55 +42 10.1 0.718 0.816 53.8 80.9 8.6 2025 10 17 13 04.23 +38 13.3 0.623 0.738 47.7 93.7 7.9 2025 10 22 14 34.12 +27 57.0 0.598 0.667 40.6 103.7 7.5 2025 10 27 15 41.37 +14 32.7 0.655 0.605 36.2 104.1 7.3 2025 11 01 16 23.57 +02 47.7 0.778 0.559 34.1 94.4 7.4 2026 01 20 17 07.84 -45 44.3 2.089 1.550 44.5 26.4 13.1 2026 01 30 17 01.99 -49 18.7 2.067 1.706 55.0 28.3 13.4 2026 02 09 16 51.31 -53 05.3 2.028 1.858 65.9 29.0 13.7 2026 02 19 16 33.02 -57 00.3 1.982 2.006 77.0 28.7 13.9 2026 03 01 16 03.10 -60 47.5 1.937 2.151 88.4 27.4 14.1 2026 03 11 15 17.26 -63 51.7 1.906 2.293 99.7 25.3 14.3 2026 03 21 14 15.52 -65 17.7 1.899 2.431 110.3 22.6 14.5 2026 03 31 13 08.95 -64 19.5 1.926 2.567 119.3 19.8 14.7 2026 04 10 12 13.36 -61 07.4 1.993 2.700 125.5 17.6 14.9 2026 04 20 11 34.86 -56 37.4 2.102 2.831 127.8 16.3 15.2 2026 04 30 11 10.86 -51 47.0 2.251 2.959 126.1 16.0 15.5 2026 05 10 10 56.94 -47 12.6 2.436 3.085 121.4 16.2 15.8 2026 05 20 10 49.70 -43 11.5 2.649 3.209 114.9 16.6 16.2 2026 05 30 10 46.91 -39 49.5 2.882 3.331 107.6 16.9 16.5 2026 06 09 10 47.12 -37 05.4 3.131 3.452 99.8 16.8 16.8 2026 06 19 10 49.41 -34 55.9 3.387 3.570 92.0 16.5 17.1 2026 06 29 10 53.15 -33 16.6 3.646 3.687 84.3 15.9 17.3 2026 07 09 10 57.90 -32 03.1 3.904 3.803 76.8 15.1 17.6 2026 07 19 11 03.38 -31 11.7 4.156 3.917 69.5 14.1 17.8 2026 07 29 11 09.34 -30 39.0 4.398 4.029 62.4 12.9 18.1 2026 08 08 11 15.62 -30 22.2 4.628 4.140 55.6 11.7 18.3 2026 08 18 11 22.09 -30 19.0 4.843 4.250 49.1 10.4 18.5 2026 08 28 11 28.60 -30 27.6 5.041 4.359 43.2 9.1 18.6 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 August 20 (CBET 5594) Daniel W. E. Green