Electronic Telegram No. 5701 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/2026 AZ_17 (BOK) An apparently asteroidal object discovered on CCD images obtained on Jan. 13 UT with the 2.25-m Bok reflector at Kitt Peak (discovery observations tabulated below) has been found to show cometary appearance. Apparently no fewer than eight separate designations were sent to the Minor Planet Center of this object, and it immediately was placed on the MPC's NEOCP webpage due to a high "NEO Digest2 score" (according to P. Veres), although it sat on the NEOCP without ever being moved to the PCCP webpage for several weeks, apparently. Finally, it was given the designation 2026 AZ_17 without the observations ever being published or made available at the MPC website (until the newly published MPEC 2026-L52), although the designation was published with a preliminary orbit on the "Daily Orbit Update" MPEC 2026-C86 on Feb. 12 -- this despite the fact that H. Groeller reported the object to be very diffuse with no tail on four co-added 60-s exposures obtained on Jan. 21.5 UT with the 1.55-m Kuiper reflector at Catalina and A. F. Tubbiolo reported a very condensed head of size 3" with a broad tail 6" long spanning p.a. 275-280 degrees on Feb. 4.5 with a 2.5-m reflector at Kitt Peak (which the MPC ignored when giving the minor-planet designation a month after the discovery). 2026 UT R.A. (2000) Decl. Mag. Jan. 13.53745 15 42 18.63 +12 21 17.8 13.54243 15 42 18.94 +12 21 18.6 22.1 13.54740 15 42 19.27 +12 21 19.7 21.8 13.55236 15 42 19.62 +12 21 20.5 22.0 R. Haver reported on the "ICQ Comet Observations" Facebook forum that he obtained forty 90-s CMOS exposures with a 0.4-m Cassegrain reflector at Frasso Sabino, Italy, on Apr. 19.0 UT that show a coma of diameter 8" and a probable tail 13" long in p.a. 233 degrees (total mag 18.8). A. Hale, Cloudcroft, NM, USA, remotely obtained 300-s CCD exposures on Apr. 21.0 with the Las Cumbres Observatory 1.0-m f/8 Schmidt-Cassegrain telescope; the stacked exposures reveal a condensed but slightly diffuse but condensed coma of size 5" with a distinct short and somewhat-broad tail 8" long in p.a. 220 degrees. One-hundred-nineteen 30-s CMOS exposures taken by L. Buzzi and A. Aletti (Varese, Italy) using a 0.36-m f/8.6 Ritchey-Chretien reflector located at Hakos, Namibia, on Apr. 21.04-21.06 show a "fuzzy" coma 7" in size, elongated at least 5" toward p.a. about 220 degrees. Two-hundred stacked 30-s unfiltered CCD images obtained by Aletti on Apr. 25.0 with a 0.36-m f/7.5 reflector at Varese show a condensed 6" coma with a faint tail 7" long in p.a. 225 degrees. Fourteen stacked 60-s CCD exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) using a 0.61-m f/6.5 astrograph located at the Sierra Remote Observatory near Auberry, CA, USA, on Apr. 21.4 UT show a 3" coma and a fan- like tail 5" long spanning 210-255 degrees; the magnitude was 19.7 as measured within a circular aperture of radius 1".6. Fifty stacked 60-s CCD exposures taken remotely by Sato on May 10.65-10.66 with a 0.25-m f/4.5 reflector at Siding Spring, NSW, Australia, show a condensed coma about 11" in diameter with a hint of a faint tail about 17" long toward p.a. about 217 degrees; the total R magnitude was measured to be 18.6. Exposures taken on Apr. 23.03 UT by M. Jaeger, G. Rhemann, and E. Prosperi with a 0.25-m f/4 reflector at Martinsberg, Oed, Austria, show a 6" coma of mag 18.8 and a 35"-long tail in p.a. 244 degrees. W. Hasubick writes that exposures taken on Apr. 26.08 with a 0.44-m reflector at Buchloe, Germany, show a condensed coma of size 14" with a straight 23" tail in p.a. 244 degrees. Twenty 120-s CMOS images obtained on May 28.33-28.35 by T. Prystavski (Lviv, Ukraine) with an iTelescope 0.51-m f/3 Cassegrain reflector in the Great Basin Desert near Beryl Junction, UT, USA, in moonlight show a slightly curved 0'.2-long tail in p.a. 184 degrees. The following orbital elements by S. Nakano (Central Bureau) are from 108 observations spanning 2026 Jan. 13-June 8 (mean residual 0".4), with corresponding "original" and "future" values of 1/a being +0.015416 and +0.015360 (+/- 0.000004) AU**-1, respectively; they indicate an osculating orbital period of 524 yr. There are no close approaches to major planets. Epoch = 2026 Nov. 16.0 TT T = 2026 Nov. 23.20969 TT Peri. = 146.90904 e = 0.9619626 Node = 149.97300 2000.0 q = 2.4726977 AU Incl. = 36.23407 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 12.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2026 06 09 16 31.63 +29 26.0 2.313 3.034 127.0 15.5 18.2 2026 06 19 16 26.54 +28 51.8 2.285 2.977 124.1 16.4 18.1 2026 06 29 16 22.46 +27 44.6 2.272 2.921 120.4 17.5 18.0 2026 07 09 16 19.95 +26 07.3 2.271 2.867 116.1 18.6 17.9 2026 07 19 16 19.41 +24 03.8 2.281 2.817 111.5 19.6 17.9 2026 07 29 16 21.08 +21 39.4 2.303 2.768 106.5 20.6 17.8 2026 08 08 16 25.03 +18 59.6 2.333 2.723 101.5 21.4 17.8 2026 08 18 16 31.23 +16 09.5 2.372 2.681 96.4 22.0 17.8 2026 08 28 16 39.58 +13 14.0 2.419 2.642 91.3 22.5 17.8 2026 09 07 16 49.93 +10 17.4 2.473 2.607 86.1 22.7 17.8 2026 09 17 17 02.11 +07 23.6 2.533 2.575 81.0 22.7 17.8 2026 09 27 17 15.96 +04 36.1 2.599 2.547 75.9 22.4 17.8 2026 10 07 17 31.29 +01 57.6 2.669 2.524 70.8 22.0 17.8 2026 10 17 17 47.95 -00 29.5 2.744 2.505 65.7 21.3 17.9 2026 10 27 18 05.74 -02 43.2 2.823 2.490 60.6 20.3 17.9 2026 11 06 18 24.49 -04 42.0 2.904 2.480 55.4 19.2 18.0 2026 11 16 18 44.03 -06 25.2 2.987 2.474 50.3 17.9 18.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 June 10 (CBET 5701) Daniel W. E. Green