Electronic Telegram No. 5000 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/2021 N2 (FULS) David Carson Fuls, Lunar and Planetary Laboratory, University of Arizona, reports the discovery of another comet in CCD images taken on July 9 with the Catalina Sky Survey's 0.68-m Schmidt reflector; Fuls described the comet as being very condensed in appearance with a very slight elongation toward p.a. 270 degrees. The discovery observations are tabulated below. Pre-discovery Catalina observations from June 27 were identified later, with measured magnitude 18.4-18.8 (but no indication of appearance). 2021 UT R.A. (2000) Decl. Mag. Observer July 9.43635 2 00 39.07 +17 24 23.0 18.3 Fuls 9.44163 2 00 39.43 +17 24 24.7 18.4 " 9.44692 2 00 39.64 +17 24 25.6 18.2 " 9.45221 2 00 39.92 +17 24 27.2 18.3 " After the comet was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists also have commented on the cometary appearance. E. Guido, Castellammare di Stabia, Italy, writes that twenty-eight stacked 60-s unfiltered exposures taken remotely by a large group of observers on July 10.15-10.16 UT with a "Telescope Live" 0.7-m f/8 Ritchey-Chretien reflector at Oria, Almeria, Spain, show a compact coma about 8" in diameter and a tail 10" long in p.a. 250 degrees; the magnitude was measured as 17.9-18.3. Eight stacked 60-s exposures taken remotely by H. Sato (Tokyo, Japan) with a 0.43-m f/6.8 astrograph located near Mayhill, NM, USA, on July 10.43 UT show a strongly condensed coma 8" in diameter with a hint of a tail 10" long toward p.a. 270 degrees; the magnitude was 18.2 as measured within a circular aperture of radius 5".7. Twenty stacked 90-s exposures taken by L. Buzzi and L. Demetz with a 0.51-m f/6.7 astrograph of the Skygems Telescope Network in Namibia on July 12.1 (and measured by A. Aletti, Buzzi, and G. Galli) show a condensed 7" coma and a short tail 10" long in p.a. 260 degrees; the magnitude was given as 18.3. Twenty stacked 120-s CCD exposures taken remotely on July 15.2 by E. Bryssinck, Kruibeke, Belgium, using a 0.5-m f/6.8 reflector at the Skygems Remote Observatory in Namibia show a strong central condensation and a compact coma 8" across with a short tail 11" long in p.a. 259 degrees. The available astrometry appears on MPEC 2021-N137. The following preliminary elliptical orbital elements by S. Nakano (CBAT) are from 64 observations spanning 2021 June 27-July 15 (mean residual 0".3), and while they suggest that the comet passed 0.49 AU from Saturn in 2015 February, the uncertainty in the orbit is such that a parabola can still fit the observations to a mean residual of 0".4. A search for additional archived observations was unsuccessful. T = 2021 Oct. 29.06229 TT Peri. = 174.78627 e = 0.4735976 Node = 221.91977 2000.0 q = 3.8245657 AU Incl. = 12.99511 a = 7.2654789 AU n = 0.05032777 P = 19.58 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 9.0 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2021 07 05 01 56.75 +17 07.9 4.119 3.888 69.9 14.2 18.0 2021 07 10 02 01.13 +17 26.4 4.047 3.883 73.5 14.5 17.9 2021 07 15 02 05.30 +17 43.3 3.974 3.878 77.2 14.8 17.9 2021 07 20 02 09.24 +17 58.6 3.899 3.873 81.0 15.0 17.8 2021 07 25 02 12.93 +18 12.2 3.825 3.868 84.9 15.2 17.8 2021 07 30 02 16.35 +18 23.9 3.750 3.864 88.8 15.2 17.7 2021 08 04 02 19.48 +18 33.8 3.675 3.860 92.8 15.2 17.7 2021 08 09 02 22.29 +18 41.7 3.600 3.856 96.9 15.1 17.6 2021 08 14 02 24.78 +18 47.4 3.526 3.852 101.1 15.0 17.6 2021 08 19 02 26.91 +18 51.0 3.454 3.849 105.4 14.7 17.5 2021 08 24 02 28.68 +18 52.3 3.383 3.845 109.8 14.3 17.5 2021 08 29 02 30.06 +18 51.3 3.315 3.842 114.3 13.9 17.4 2021 09 03 02 31.05 +18 47.8 3.248 3.840 118.9 13.3 17.4 2021 09 08 02 31.63 +18 41.8 3.185 3.837 123.7 12.6 17.4 2021 09 13 02 31.79 +18 33.2 3.126 3.835 128.6 11.8 17.3 2021 09 18 02 31.56 +18 22.1 3.071 3.833 133.5 11.0 17.3 2021 09 23 02 30.93 +18 08.4 3.020 3.831 138.6 10.0 17.2 2021 09 28 02 29.93 +17 52.2 2.974 3.829 143.8 8.9 17.2 2021 10 03 02 28.57 +17 33.6 2.934 3.828 149.1 7.7 17.2 2021 10 08 02 26.90 +17 12.8 2.900 3.827 154.5 6.4 17.1 2021 10 13 02 24.96 +16 49.9 2.873 3.826 160.0 5.1 17.1 2021 10 18 02 22.82 +16 25.2 2.852 3.825 165.6 3.7 17.1 2021 10 23 02 20.52 +15 59.2 2.838 3.825 171.2 2.3 17.1 2021 10 28 02 18.13 +15 32.3 2.832 3.825 176.6 0.9 17.1 2021 11 02 02 15.72 +15 04.7 2.833 3.825 176.9 0.8 17.1 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2021 CBAT 2021 July 15 (CBET 5000) Daniel W. E. Green