------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 1218 1997 Jul 28 15.25UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK GMH at AST.STAR.RL.AC.UK WORLD WIDE WEB http://www.demon.co.uk/astronomer ------------------------------------------------------------------- COMET P/1997 N2 (HELIN-ROMAN-ALU 2) Comet P/1989 U1 (= 1989y = 1989 XVI) has been recovered on CCD frames obtained by C. W. Hergenrother with the Smithsonian Astrophysical Observatory's 1.2-m reflector on Mt. Hopkins. Candidate images among several measured by T. B. Spahr and motion-checked by G. V. Williams show some possible very slight diffuseness on July 13, and this is more evident on a coaddition of the two-night total exposure of 12 min, a short tail then also being evident in p.a. 250 deg. The indicated correction to the prediction by B. G. Marsden on MPC 23483 (ephemeris on MPC 29154) is Delta T = -0.6 day. 1997 UT R.A. (2000) Decl. m2 July 13.45823 1 00 00.27 + 7 36 20.4 13.46002 1 00 00.43 + 7 36 20.9 13.46183 1 00 00.59 + 7 36 21.8 14.43271 1 01 26.89 + 7 43 01.7 19.6 14.43450 1 01 27.06 + 7 43 02.7 14.43628 1 01 27.21 + 7 43 03.3 The following orbital elements by Williams satisfy 16 observations 1989-1997 with mean residual 1".0: Epoch = 1997 Nov. 8.0 TT T = 1997 Nov. 10.0833 TT Peri. = 220.9513 e = 0.531645 Node = 178.4818 2000.0 q = 1.910084 AU Incl. = 5.7751 a = 4.078279 AU n = 0.1196709 P = 8.236 years IAUC 6704 Ephemeris by G.Hurst using EPH.EXE by N.James. The magnitude formula, based on m1 predictions, is taken from the ICQ 1997 Handbook. m = 11.5 + 5.0 log R + 15.0 log r Date R.A. (2000) Dec. R r Elong Mag. Motion h m o ' (AU) (AU) o "/hr P.A. 1997 July 26.00 1 18.07 +8 54.9 1.683 2.135 101.7 17.6 53 75 31.00 1 24.92 +9 21.1 1.616 2.116 104.8 17.4 51 76 1997 Aug 5.00 1 31.51 +9 43.9 1.551 2.098 107.9 17.3 49 78 10.00 1 37.79 +10 3.1 1.487 2.080 111.1 17.1 46 79 15.00 1 43.73 +10 18.3 1.426 2.063 114.5 17.0 43 81 20.00 1 49.28 +10 29.3 1.368 2.047 117.9 16.8 40 84 25.00 1 54.39 +10 35.8 1.311 2.032 121.5 16.7 36 87 30.00 1 59.01 +10 37.6 1.258 2.017 125.3 16.6 32 91 1997 Sept 4.00 2 3.07 +10 34.4 1.207 2.003 129.2 16.4 28 96 9.00 2 6.53 +10 26.2 1.160 1.990 133.3 16.3 24 103 14.00 2 9.36 +10 12.8 1.116 1.978 137.5 16.2 20 113 19.00 2 11.52 +9 54.4 1.076 1.967 142.0 16.1 17 128 24.00 2 13.00 +9 31.2 1.040 1.957 146.6 16.0 15 147 29.00 2 13.78 +9 3.5 1.008 1.948 151.4 15.9 15 167 Guy M Hurst