Periodic Comet d'Arrest

The following prediction, derived by B. G. Marsden from observations during 1950-1971 and with consideration of perturbations by all nine planets and nongravitational effects, differs slightly from that in Handb. Br. Astron. Assoc. for 1976. The uncertainty is several times this difference, possibly up to Delta-T = +/- 0.2 day (cf. Marsden et al. 1973, Astron. J. 78, 211). T = 1976 Aug 12.8401 ET Epoch = 1976 Aug. 10.0 ET Peri. = 178.9271 e = 0.656142 Node = 141.3513 1950.0 a = 3.385149 AU Incl. = 16.6898 n = 0.1582477 q = 1.164009 AU P = 6.228 years For dT = +1d 1976/77 ET R. A. (1950) Decl. Delta r dR.A. dDecl. m2 Feb. 12 16 03.00 - 3 46.4 2.256 2.349 -1m21 + 4'5 21.0 22 16 18.74 - 3 18.7 -1.38 + 4.9 Mar. 3 16 34.34 - 2 35.0 1.875 2.191 -1.57 + 5.4 20.3 13 16 49.66 - 1 34.0 -1.80 + 5.9 23 17 04.63 - 0 14.6 1.517 2.029 -2.07 + 6.5 19.5 Apr. 2 17 19.09 + 1 24.1 -2.40 + 7.1 12 17 32.90 + 3 22.3 1.195 1.867 -2.81 + 7.8 18.6 22 17 45.97 + 5 39.4 -3.31 + 8.5 May 2 17 58.15 + 8 13.5 0.918 1.706 -3.93 + 9.0 17.6 12 18 09.37 +11 00.4 -4.70 + 9.3 22 18 19.70 +13 53.9 0.688 1.550 -5.65 + 8.9 16.6 June 1 18 29.26 +16 43.9 -6.84 + 7.4 11 18 38.56 +19 16.0 0.502 1.407 -8.28 + 4.1 15.5 21 18 48.54 +21 11.9 -10.04 - 1.3 July 1 19 00.71 +22 04.6 0.349 1.286 -12.17 - 8.8 14.3 6 19 08.41 +21 55.0 -13.40 -13.1 11 19 17.77 +21 12.6 0.283 1.238 -14.78 -17.2 13.7 16 19 29.31 +19 47.4 -16.34 -20.6 21 19 43.65 +17 26.0 0.224 1.201 -18.11 -22.3 13.1 26 20 01.47 +13 50.9 -20.13 -20.9 31 20 23.47 + 8 43.4 0.178 1.176 -22.41 -15.1 12.5 Aug. 5 20 50.09 + 1 53.2 -24.90 - 4.8 10 21 21.12 - 6 24.6 0.153 1.165 -27.42 + 6.8 12.1 15 21 55.30 -15 15.5 -29.62 +12.4 20 22 30.36 -23 23.0 0.160 1.168 -31.01 + 5.7 12.2 25 23 03.66 -29 51.5 -31.16 -12.0 30 23 33.08 -34 28.4 0.196 1.185 -29.98 -32.8 12.7 Sept. 4 23 57.61 -37 29.5 -27.75 -49.6 9 0 17.16 -39 18.6 0.249 1.215 -24.98 -59.7 13.3 14 0 32.20 -40 16.0 -22.11 -63.3 19 0 43.48 -40 36.0 0.313 1.257 -19.42 -62.3 14.0 29 0 57.82 -39 57.4 -14.93 -53.7 Oct. 9 1 05.61 -38 07.6 0.463 1.369 -11.58 -42.9 15.2 19 1 10.39 -35 31.7 -9.08 -33.4 29 1 14.41 -32 25.1 0.649 1.508 -7.19 -26.1 16.3 Nov. 8 1 18.98 -29 00.8 -5.76 -20.7 18 1 24.59 -25 29.3 0.877 1.661 -4.66 -16.8 17.4 28 1 31.48 -21 57.7 -3.81 -13.9 Dec. 8 1 39.64 -18 31.4 1.154 1.821 -3.16 -11.7 18.4 18 1 48.93 -15 13.7 -2.65 -10.0 28 1 59.24 -12 06.3 1.476 1.983 -2.25 - 8.7 19.3 Jan. 7 2 10.43 - 9 10.5 -1.93 - 7.5 17 2 22.34 - 6 26.4 1.833 2.145 -1.67 - 6.6 20.1 27 2 34.87 - 3 54.2 -1.46 - 5.8 Feb. 6 2 47.93 - 1 33.7 2.212 2.304 -1.29 - 5.0 20.8 16 3 01.41 + 0 35.4 -1.15 - 4.4 26 3 15.25 + 2 33.4 2.599 2.460 -1.03 - 3.9 21.5 m2 = 15.5 + 5 log Delta + 10 log r J. Bortle, Brooks Observatory, notes that this comet has undergone considerable brightness surges closely following perihelion passage at almost every apparition. Based on a study of observations 1857-1970, and assuming the maximum of the surge to occur 20 days after perihelion, he provides the following predictions for m1: 1976 ET m1 1976 ET m1 1976 ET m1 June 11 13.5 Aug. 10 9.2 Oct. 9 8.8 July 1 12.3 20 8.4 29 10.5 11 11.7 30 6.2 Nov. 18 11.8 21 11.1 Sept. 9 6.7 Dec. 8 13.2 31 10.5 19 7.4