Electronic Telegram No. 5707 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/2026 M1 = P/2021 N1 (ZTF) The Minor Planet Center has apparently identified accidental recovery observations of comet P/2021 N1 (cf. CBET 4999) that were reported as an apparently asteroidal object when found on CCD images taken on June 22.6 UT with a 0.5-m f/2 Schmidt reflector at Haleakala, Hawaii, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program (recovery observations tabulated below). 2026 UT R.A. (2000) Decl. Mag. June 22.56465 23 25 50.69 -35 05 34.3 16.6 22.57060 23 25 54.21 -35 04 51.0 16.8 22.58202 23 26 00.96 -35 03 27.8 16.5 22.58613 23 26 03.41 -35 02 57.5 16.5 The available astrometry is posted via a link at the bottom of the MPC's oddly named "Recovery Page Criteria" (the ATLAS observations were originally posted as a new discovery on the MPC's NEOCP webpage). The Central Bureau learned of the recovery from H. Sato (Bunkyo-ku, Tokyo, Japan) when he sent follow-up CMOS astrometry of this comet obtained remotely on June 23.3 UT with a 0.25-m f/3.8 astrograph located at Rio Hurtado, Chile, when he noted a strongly condensed coma 15" in diameter and a tail 50" long toward p.a. 250 degrees; the magnitude was 16.1 as measured within a circular aperture of radius 8".7. M. Mattiazzo (Swan Hill, Vic., Australia) writes that eleven stacked 30-s CMOS images obtained on June 23.74 with a 0.43-m f/6.8 reflector located at Siding Spring, NSW, show a moderately compact coma 0'.23 in diameter with a 2'-long tail in p.a. 250 deg, with total mag 16.2. M. Masek, Institute of Physics of the Czech Academy of Sciences, writes that he obtained follow-up unfiltered CCD imaging of comet P/2021 N1 with a 25-cm Schmidt-Cassegrain reflector at the site of the future Cherenkov Telescope Array at La Palma, Canary Islands, on June 24.19 that show a 0'.4 condensed coma of total mag 15.6 with a tail 1'.1 long in p.a. 251 degrees. The residuals for the recovery observations were -4.0 deg in R.A. and -7.5 deg in Decl. with respect to a prediction on NK 5576, with a correction of Delta(T) = +1.5 days; a correction from the prediction in the ICQ's 2026 Comet Handbook is Delta(T) = +2.1 days. The following linked orbital elements by S. Nakano (Central Bureau) are from 117 observations spanning 2021 June 17-2026 June 26 (mean residual 0".5). The comet passed 0.52 AU from Jupiter on 2003 Apr. 6 and will pass 0.17 AU from the earth on 2026 June 29. The comet will pass 0.82 AU from Jupiter on 2038 Sept. 7 UT. Epoch = 2000 Sept.13.0 TT T = 2000 Sept. 6.30121 TT Peri. = 15.69423 e = 0.6504598 Node = 306.22774 2000.0 q = 1.0592929 AU Incl. = 13.84953 a = 3.0305325 AU n = 0.18682098 P = 5.28 years Epoch = 2005 Dec. 16.0 TT T = 2005 Dec. 20.38486 TT Peri. = 21.07648 e = 0.6735578 Node = 301.22597 2000.0 q = 0.9758312 AU Incl. = 11.48760 a = 2.9892923 AU n = 0.19070036 P = 5.17 years Epoch = 2011 Feb. 8.0 TT T = 2011 Feb. 20.83540 TT Peri. = 21.18836 e = 0.6740479 Node = 301.17264 2000.0 q = 0.9735341 AU Incl. = 11.48442 a = 2.9867400 AU n = 0.19094485 P = 5.16 years Epoch = 2016 Apr. 2.0 TT T = 2016 Apr. 15.86555 TT Peri. = 21.21545 e = 0.6758780 Node = 301.12766 2000.0 q = 0.9661081 AU Incl. = 11.48984 a = 2.9806927 AU n = 0.19152623 P = 5.15 years Epoch = 2021 May 26.0 TT T = 2021 June 6.55768 TT Peri. = 21.19089 e = 0.6769307 Node = 301.14414 2000.0 q = 0.9619964 AU Incl. = 11.50455 a = 2.9776785 AU n = 0.19181712 P = 5.14 years Epoch = 2026 July 19.0 TT T = 2026 July 28.48699 TT Peri. = 21.21972 e = 0.6758212 Node = 301.11368 2000.0 q = 0.9663168 AU Incl. = 11.48539 a = 2.9808141 AU n = 0.19151453 P = 5.15 years Epoch = 2031 Sept.11.0 TT T = 2031 Sept.18.85805 TT Peri. = 21.18619 e = 0.6749825 Node = 301.09418 2000.0 q = 0.9694766 AU Incl. = 11.47071 a = 2.9828445 AU n = 0.19131902 P = 5.15 years Epoch = 2036 Nov. 3.0 TT T = 2036 Nov. 15.23221 TT Peri. = 21.28797 e = 0.6745334 Node = 301.03065 2000.0 q = 0.9715950 AU Incl. = 11.45541 a = 2.9852376 AU n = 0.19108902 P = 5.16 years Epoch = 2042 Mar. 17.0 TT T = 2042 Mar. 2.62751 TT Peri. = 23.76000 e = 0.6590767 Node = 299.48298 2000.0 q = 1.0378872 AU Incl. = 10.66239 a = 3.0443425 AU n = 0.18555121 P = 5.31 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 18.0 and 2.5n = 10 for the magnitudes (which is a magnitude fainter than the parameters used for the 2021 return). Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2026 06 09 21 05.61 -50 55.7 0.260 1.188 126.5 43.3 15.8 2026 06 19 22 48.51 -41 30.8 0.194 1.115 116.2 54.8 14.9 2026 06 29 00 26.80 -19 40.3 0.165 1.053 98.4 72.7 14.3 2026 07 09 01 39.75 +05 24.5 0.186 1.006 81.4 88.1 14.4 2026 07 19 02 31.39 +22 11.7 0.239 0.976 73.6 92.8 14.8 2026 07 29 03 10.68 +31 49.6 0.307 0.966 72.1 90.3 15.3 2026 08 08 03 43.07 +37 34.2 0.376 0.978 73.8 84.6 15.8 2026 08 18 04 10.56 +41 13.5 0.441 1.010 77.1 77.7 16.3 2026 08 28 04 33.37 +43 41.1 0.497 1.059 81.7 70.7 16.7 2026 09 07 04 50.97 +45 26.2 0.543 1.122 87.3 63.8 17.2 2026 09 17 05 02.29 +46 44.5 0.580 1.196 94.1 57.0 17.6 2026 09 27 05 06.31 +47 42.7 0.607 1.277 102.2 50.1 18.0 2026 10 07 05 02.27 +48 19.5 0.630 1.363 111.5 43.0 18.3 2026 10 17 04 50.02 +48 25.3 0.652 1.452 122.0 35.6 18.7 2026 10 27 04 31.11 +47 45.8 0.680 1.543 133.4 27.9 19.0 2026 11 06 04 08.86 +46 11.6 0.721 1.634 144.7 20.5 19.4 2026 11 16 03 47.41 +43 47.6 0.780 1.725 154.3 14.4 19.8 2026 11 26 03 30.16 +40 54.6 0.861 1.816 158.6 11.5 20.3 2026 12 06 03 18.49 +37 58.5 0.965 1.905 155.2 12.5 20.7 2026 12 16 03 12.35 +35 18.8 1.093 1.994 147.4 15.4 21.2 2026 12 26 03 10.99 +33 06.0 1.241 2.081 138.3 18.3 21.7 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 June 27 (CBET 5707) Daniel W. E. Green